Magnetic sensor and magnetic measurement method

Abstract

A magnetic sensor 1 according to the present invention, which makes it possible to remove 1 / f noise and measure a small magnetic field with high accuracy, comprises a variable magnetic field detection unit 100a including: a first magnetic body 31 magnetized by a measurement magnetic field in a first direction (X direction); a magnetic detection element 10a that is positioned on one first-direction side (X1 side) relative to a first end part 311 of the first magnetic body 31, the first end part 311 being the end part of the first magnetic body 31 on the one first-direction side, and that has a sensitivity axis extending along the first direction; a variable-magnetic-state member 40 that is positioned on the one first-direction side relative to the first end part 311 of the first magnetic body 31 and is capable of assuming a first state and a second state which differ in terms of a magnetic state, including at least one of effective magnetic permeability and direction of magnetization; and a magnetic state modulation member 20 for changing the magnetic state of the variable-magnetic-state member 40.

Description

Magnetic sensor and magnetic measurement method

[0001] The present invention relates to a magnetic sensor including a magnetoresistive element and a magnetic measurement method.

[0002] Some magnetic sensors that detect and measure magnetic fields include a magnetoresistive element that uses the GMR (giant magnetoresistance) effect or the TMR (tunneling magnetoresistance) effect. The magnetoresistive element in these magnetic sensors has a structure in which a pinned magnetic layer, a non-magnetic intermediate layer, and a free magnetic layer are stacked in this order. In the magnetoresistive element, when an external magnetic field to be measured is applied, the magnetization direction of the free magnetic layer changes, causing a resistance change according to the angle between the magnetization direction of the free magnetic layer and the magnetization direction of the pinned magnetic layer. A magnetic sensor that includes a magnetoresistive element can detect a magnetic field using the resistance change of the magnetoresistive element.

[0003] Magnetic sensors equipped with magnetoresistive elements have 1 / f noise that cannot be removed by filters. 1 / f noise is inversely proportional to frequency, becoming larger as the frequency decreases, which can hinder high-precision measurements. Therefore, various methods are used to remove 1 / f noise.

[0004] Patent Document 1 discloses an even-function magnetic sensor that removes 1 / f noise by taking the difference between the output when a bias magnetic field is applied in a certain direction (+X direction) and the output when a bias magnetic field is applied in the opposite direction (-X direction).

[0005] Patent Document 2 discloses a measuring device that, when measuring the Hall electromotive force of a semiconductor sample, shifts the frequency band of the voltage difference Vm to the lower frequency side in order to remove noise due to a Schottky barrier that occurs between an electrode and a sample, thereby removing the frequency band of the voltage difference Vm that is significantly affected by 1 / f noise.

[0006] Patent Document 3 discloses a magnetic field sensing device that samples bridge signals at a first current and a second current by switching between two sample holds, and determines the value of the magnetic field from the difference between the sampled first and second bridge signals.

[0007] Patent Document 4 discloses a sensor device that uses a modulator to switch the positive and negative sides of a sensor signal and obtain the difference between the modulated signals in order to remove 1 / f noise from the output signal.

[0008] Japanese Patent Application Laid-Open No. 2018-115972 Japanese Patent Application Laid-Open No. 2020-148727 Special Publication No. 2012-518788 Special Publication No. 2009-544004

[0009] A magnetic sensor equipped with a magnetoresistive element has a problem in that 1 / f noise in the low frequency range reduces the detection accuracy of the magnetic sensor, and various devices and methods have been proposed to solve this problem. The object of the present invention is to provide a magnetic sensor equipped with a magnetoresistive element and a magnetic measurement method that can remove 1 / f noise using a configuration different from conventional ones and measure small magnetic fields with high accuracy.

[0010] In one aspect, the present invention is a magnetic sensor characterized by comprising a variable magnetic field detection unit having: a first magnetic body that is magnetized by a measurement magnetic field in a first direction; a magnetic detection element that is located on one side of a first end of the first magnetic body in the first direction and has a sensitivity axis along the first direction; a magnetic state variable member that is located on one side of the first end of the first magnetic body in the first direction and can take a first state and a second state in which the magnetic states differ, including at least one of effective permeability and magnetization direction; and a magnetic state modulation member that changes the magnetic state of the magnetic state variable member.

[0011] In such a magnetic sensor, by using two outputs from the magnetic field detection unit when the magnetic state variable member is in different states, a signal with 1 / f noise removed can be obtained when measuring the measurement magnetic field, which is the external magnetic field to be measured.

[0012] The magnetic sensor may further include a magnetic field calculation unit that calculates the measured magnetic field based on a first output from the variable magnetic field detection unit when the magnetic state variable member is in the first state and a second output from the variable magnetic field detection unit when the magnetic state variable member is in the second state. The magnetic field calculation unit can calculate a signal from which 1 / f noise has been removed.

[0013] In the above magnetic sensor, the effective permeability μ2 in the first direction of the magnetic state changeable member in the second state may be higher than the effective permeability μ1 in the first direction of the magnetic state changeable member in the first state, and may also be higher than the permeability μ0 in the first direction of a first material located between the first magnetic body and the magnetic detection element.

[0014] In this way, because the effective magnetic permeability of the magnetic state changeable member in the second state is higher than that of the surrounding magnetic field, the magnetic flux based on the measured magnetic field, i.e., the magnetic flux of the measured magnetic field and the magnetic flux generated when the first magnetic body is magnetized by the measured magnetic field, tends to concentrate in the magnetic state changeable member. As a result, the density of the magnetic flux reaching the magnetically sensitive portion of the magnetic detector element when the magnetic state changeable member is in the second state tends to differ from the density of the magnetic flux reaching the magnetically sensitive portion of the magnetic detector element when the magnetic state changeable member is in the first state.

[0015] In one embodiment (first embodiment) of the above-mentioned magnetic sensor, the variable magnetic field detection unit may have a non-magnetic member between the magnetic detection element and the magnetic state variable member, and the magnetic sensing portion of the magnetic detection element may be magnetically uncoupled from the magnetic state variable member.

[0016] When the magnetic sensing part of the magnetic detector element and the magnetic state variable member are magnetically uncoupled, in the second state in which the magnetic state variable member is more likely to collect magnetic flux based on the measured magnetic field, the magnetic flux based on the measured magnetic field is less likely to reach the magnetic sensing part of the magnetic detector element.

[0017] In another embodiment (second embodiment) of the magnetic sensor described above, the magnetic sensing portion of the magnetic detector element may be magnetically coupled to the magnetic state variable member.

[0018] When the magnetic sensing part of the magnetic detector element and the magnetic state variable member are magnetically coupled, in the second state in which the magnetic state variable member is more likely to collect magnetic flux based on the measured magnetic field, the magnetic flux based on the measured magnetic field also more easily reaches the magnetic sensing part of the magnetic detector element.

[0019] In the magnetic sensor having the magnetic detector element and magnetic state changeable member, the magnetic detector element and the magnetic state changeable member may be aligned in a second direction perpendicular to the first direction. In this case, the magnetic state changeable member may have a portion closer to the first magnetic body in the first direction than the detection center of the magnetic detector element. Furthermore, the center of the magnetic state changeable member in the first direction and the detection center of the magnetic detector element may be at the same position in the first direction, and the length of the magnetic state changeable member in the first direction may be longer than the length of the magnetic detector element in the first direction. The length of the first magnetic body in the first direction may be longer than the length in the second direction.

[0020] The variable magnetic field detection unit of the magnetic sensor may further include a second magnetic body that is more distal in the first direction than the magnetic detection element when viewed from the first end.

[0021] By positioning the magnetic detector element between the first magnetic body and the second magnetic body in the first direction, the magnetic flux based on the measured magnetic field can be made to reach the magnetic detector element efficiently.

[0022] In this case, the magnetic state changeable member may be arranged so as to be magnetically coupled to the first magnetic body and the second magnetic body in the second state. In this case, the measurement magnetic field passes preferentially through the magnetically coupled portion consisting of the first magnetic body, the magnetic state changeable member, and the second magnetic body, thereby making it possible to increase the difference in magnetic flux density reaching the magnetically sensitive portion of the magnetic detector element compared to when the magnetic state changeable member is not magnetically coupled to the first magnetic body or the second magnetic body.

[0023] In the magnetic sensor of the first embodiment or the magnetic sensor of the second embodiment, the magnetic state modulation member and the magnetic state changeable member may form a magnetic control body stacked in a second direction perpendicular to the first direction, and the magnetic control body and the magnetic detector element may be arranged side by side in the second direction. In this case, the magnetic state modulation member may have a spin torque generation unit that imparts a spin orbit torque to the magnetic state changeable member when current is applied, and the magnetic state of the magnetic state changeable member when current is applied may differ from the magnetic state when current is not applied, based on the spin orbit torque from the spin torque generation unit.

[0024] By using spin-orbit torque to change the magnetic state of the magnetic state-variable member, it is possible to increase the degree of difference between the magnetic states of the first and second states and to facilitate switching between states.

[0025] In one specific example (Type A) of using the above-mentioned spin orbit torque, the variable magnetic field detection unit may include a bias magnetic field source that magnetizes the magnetic state variable member along the second direction to an extent that the magnetization does not rotate due to the measurement magnetic field when the magnetic state modulation member is in a non-conductive state. In this case, the magnetic state variable member may be in the first state when the magnetic state modulation member is in a non-conductive state, and may be in the second state when the magnetic state modulation member is in a conductive state and a current flows in an in-plane direction of a first surface having a normal along the second direction, and in the second state, the magnetic state variable member may be magnetized in a direction opposite to the direction of the current flow to an extent that the magnetization can rotate in the in-plane direction of the first surface due to a magnetic field based on the measurement magnetic field when subjected to the spin orbit torque.

[0026] In the first state, the magnetization direction of the magnetic state changeable member is fixed by the bias magnetic field, so the magnetic field based on the measured magnetic field is less likely to concentrate on the magnetic state changeable member. In contrast, in the second state, the magnetic state changeable member is magnetized by the magnetic flux based on the measured magnetic field, so the magnetic flux based on the measured magnetic field concentrates on the magnetization state changeable member. Therefore, the magnetic flux density reaching the magnetic detector element located around the magnetic state changeable member differs between the first state and the second state.

[0027] In this case, in the second state, the current flowing through the magnetic state modulation member may be in a third direction that is an in-plane direction of the first surface and perpendicular to the first direction, which may reduce hysteresis.

[0028] In a specific example of Type A, the form of the bias magnetic field source is not limited. The magnetic state modulation member may have an antiferromagnetic portion made of antiferromagnetic material, and the exchange coupling between the antiferromagnetic portion and the magnetic state variable member may serve as the bias magnetic field source. Alternatively, the bias magnetic field source may include at least one of a coil that generates an induced magnetic field when current is applied and a permanent magnet, and in this case, the bias magnetic field source may be laminated on the magnetic control body.

[0029] In another specific example (Type B) of using the above-mentioned spin orbit torque, when the magnetic state modulation member is in an energized state and a current flows along the first direction, the magnetic state changeable member is in the first state, and in the first state, the magnetic state changeable member is subjected to the spin orbit torque and is magnetized in a third direction perpendicular to the first direction and the second direction by a magnetic flux based on the measured magnetic field, and the magnetization of the magnetic state changeable member is less likely to rotate by the magnetic flux based on the measured magnetic field than in the second state, and when the magnetic state modulation member is in a de-energized state, the magnetic state changeable member is in the second state, and in the second state, the magnetization of the magnetic state changeable member is more likely to orient in the first direction by the magnetic flux based on the measured magnetic field than in the first state.

[0030] In the first state, the magnetization direction of the magnetic state changeable member is fixed based on the spin orbit torque, so the magnetic field based on the measured magnetic field is less likely to concentrate on the magnetic state changeable member. In contrast, in the second state, the magnetic state changeable member is magnetized by the magnetic flux based on the measured magnetic field, so the magnetic flux based on the measured magnetic field concentrates on the magnetization state changeable member. Therefore, the magnetic flux density reaching the magnetic detector element located around the magnetic state changeable member differs between the first state and the second state.

[0031] In a specific example of Type B, the variable magnetic field detection unit may have a bias magnetic field source that applies a bias magnetic field to the magnetic state changeable member. The bias magnetic field source may take various forms, as in the specific example of Type A. In this case, the bias magnetic field that the magnetic state changeable member receives in the second state is along the in-plane direction of a first surface having a normal along the second direction, and may be such that the magnetization of the magnetic state changeable member can be rotated by a magnetic flux based on the measured magnetic field.

[0032] In the second state, a bias magnetic field is applied to the magnetic state-changeable member, thereby reducing hysteresis.

[0033] The bias magnetic field is oriented along a third direction perpendicular to the first and second directions, thereby realizing a more stable reduction in hysteresis.

[0034] In another specific example (Type C) of using the above-mentioned spin orbit torque, when the magnetic state modulation member is in an energized state and a current flows along the first direction, the magnetic state changeable member is in the first state, and in the first state, the magnetic state changeable member is subjected to the spin orbit torque and is magnetized in the first direction and the second direction by a magnetic flux based on the measured magnetic field, and the magnetization of the magnetic state changeable member is less likely to rotate by the magnetic flux based on the measured magnetic field than in the second state, and when the magnetic state modulation member is in a de-energized state, the magnetic state changeable member is in the second state, and in the second state, the magnetization of the magnetic state changeable member is more likely to orient in the first direction by the magnetic flux based on the measured magnetic field than in the first state.

[0035] In the first state, the magnetization direction of the magnetic state changeable member is fixed based on the spin orbit torque, so the magnetic field based on the measured magnetic field is less likely to concentrate on the magnetic state changeable member. In contrast, in the second state, the magnetic state changeable member is magnetized by the magnetic flux based on the measured magnetic field, so the magnetic flux based on the measured magnetic field concentrates on the magnetization state changeable member. Therefore, the magnetic flux density reaching the magnetic detector element located around the magnetic state changeable member differs between the first state and the second state.

[0036] In a specific example of Type C, the variable magnetic field detection unit may have a bias magnetic field source that applies a bias magnetic field to the magnetic state changeable member. The form of the bias magnetic field source in this case is the same as in the specific example of Type A. The direction and strength of the bias magnetic field are the same as in the specific example of Type B. Specifically, the bias magnetic field may be along an in-plane direction of a first surface having a normal along the second direction, to an extent that the magnetization of the magnetic state changeable member can be rotated by a magnetic flux based on the measurement magnetic field, or may be along a third direction orthogonal to the first direction and the second direction.

[0037] In another aspect, the present invention provides a magnetic measurement method using a magnetic sensor including a variable magnetic field detection unit having: a first magnetic body that is magnetized by a measurement magnetic field in a first direction; a magnetic detection element that is located on one side of a first end of the first magnetic body in the first direction and has a sensitivity axis along the first direction; a magnetic state changeable member that is located on the one side of the first end of the first magnetic body in the first direction and can take a first state and a second state in which the magnetic states differ, including at least one of effective permeability and magnetization direction; and a magnetic state modulation member that changes the magnetic state of the magnetic state changeable member; and a magnetic field calculation unit that calculates the measurement magnetic field from a first output from the variable magnetic field detection unit when the magnetic state changeable member is in the first state and a second output from the variable magnetic field detection unit when the magnetic state changeable member is in the second state. This magnetic measurement method includes a first measurement step of setting the magnetic state variable member to the first state and obtaining the first output when the measurement magnetic field is applied, a second measurement step of setting the magnetic state variable member to the second state and obtaining the second output when the measurement magnetic field is applied, and a magnetic field calculation step of calculating the measurement magnetic field from the first output and the second output in the magnetic field calculation unit.

[0038] The magnetic field calculation step calculates a measured magnetic field based on the first output acquired in the first measurement step and the second output acquired in the second measurement step, thereby obtaining a measured magnetic field from which the 1 / f noise of the magnetoresistive element has been removed. For example, the 1 / f noise can be removed from the first output by using the difference between the first output and the second output in the magnetic field calculation step.

[0039] According to the present invention, since 1 / f noise can be removed from the measured magnetic field, it is possible to provide a magnetic sensor and a magnetic measurement method with high magnetic resolution that can measure a small magnetic field with high accuracy.

[0040] A block diagram of a magnetic sensor according to an embodiment of the present invention. An explanatory diagram of a magnetic field detection unit included in the magnetic sensor according to an embodiment of the present invention. A diagram for explaining a variable magnetic field detection unit (the magnetic state of the magnetically variable member is in the first state) included in the magnetic sensor according to the first embodiment of the present invention. A diagram for explaining a variable magnetic field detection unit (the magnetic state of the magnetically variable member is in the second state) included in the magnetic sensor according to the first embodiment of the present invention. A flowchart for explaining a magnetic measurement method using the magnetic sensor according to the first embodiment of the present invention. An explanatory diagram of a preferred example of the variable magnetic field detection unit included in the magnetic sensor according to the first embodiment of the present invention. An explanatory diagram of another example of a preferred example of the variable magnetic field detection unit included in the magnetic sensor according to the first embodiment of the present invention. An explanatory diagram of another example of a preferred example of the variable magnetic field detection unit included in the magnetic sensor according to the first embodiment of the present invention. An explanatory diagram of a modified example of the variable magnetic field detection unit included in the magnetic sensor according to the first embodiment of the present invention. A diagram for explaining a variable magnetic field detection unit (the magnetic state of the magnetically variable member is in the second state) included in the magnetic sensor according to the second embodiment of the present invention. A diagram for explaining a preferred example of the variable magnetic field detection unit (the magnetic state of the magnetically variable member is in the second state) included in the magnetic sensor according to the second embodiment of the present invention. A diagram for explaining the state before a measurement magnetic field is applied to a variable magnetic field detection unit (the magnetic state of the magnetically variable member is in the first state) included in a magnetic sensor according to an example (Example 1-1) in which the variable magnetic field detection unit is of type A and has the configuration of the first embodiment (the magnetically variable member 40 and the magnetosensitive portion of the magnetic detection element are magnetically uncoupled). A diagram for explaining the state in which a measurement magnetic field is applied to a variable magnetic field detection unit (the magnetic state of the magnetically variable member is in the first state) included in the magnetic sensor according to Example 1-1. A diagram for explaining the state before a measurement magnetic field is applied to a variable magnetic field detection unit (the magnetic state of the magnetically variable member is in the second state) included in the magnetic sensor according to Example 1-1. A diagram for explaining the state in which a measurement magnetic field is applied to a variable magnetic field detection unit (the magnetic state of the magnetically variable member is in the second state) included in the magnetic sensor according to Example 1-1. A diagram for explaining the state before a measurement magnetic field is applied to a variable magnetic field detection unit (the magnetic state of the magnetically variable member is in the first state) included in a magnetic sensor according to an example (Example 1-2) in which the variable magnetic field detection unit is of type A and has the configuration of the second embodiment (the magnetically variable member 40 and the magnetosensitive portion of the magnetic detection element are magnetically coupled).1-3 is a diagram illustrating a state in which a measurement magnetic field is applied to a variable magnetic field detection unit (the magnetic state of the magnetic state variable member is in a first state) included in the magnetic sensor according to Example 1-2. FIG. 1-4 is a diagram illustrating a state before a measurement magnetic field is applied to a variable magnetic field detection unit (the magnetic state of the magnetic state variable member is in a second state) included in the magnetic sensor according to Example 1-2. FIG. 1-5 is a diagram illustrating a state before a measurement magnetic field is applied to a variable magnetic field detection unit (the magnetic state of the magnetic state variable member is in a second state) included in the magnetic sensor according to Example 1-2. FIG. 1-6 is a diagram illustrating a state before a measurement magnetic field is applied to a variable magnetic field detection unit (the magnetic state of the magnetic state variable member is in a first state) included in a magnetic sensor according to Example 2-1, which has a configuration in which the variable magnetic field detection unit is Type B and the first embodiment (the magnetic state variable member 40 and the magnetic sensing unit of the magnetic detector element are magnetically uncoupled). FIG. 1-7 is a diagram illustrating a state after a measurement magnetic field is applied to a variable magnetic field detection unit (the magnetic state of the magnetic state variable member is in a first state) included in the magnetic sensor according to Example 2-1. 2-1 is a diagram illustrating a state before a measurement magnetic field is applied to a variable magnetic field detection unit (the magnetic state of the magnetic state variable member is in a second state) included in the magnetic sensor according to Example 2-1. FIG. 2-2 is a diagram illustrating a state after a measurement magnetic field is applied to a variable magnetic field detection unit (the magnetic state of the magnetic state variable member is in a second state) included in the magnetic sensor according to Example 2-1. FIG. 2-3 is a diagram illustrating a state before a measurement magnetic field is applied to a variable magnetic field detection unit (the magnetic state of the magnetic state variable member is in a first state) included in a magnetic sensor according to an example (Example 2-2) having a configuration in which the variable magnetic field detection unit is Type B and the second embodiment (the magnetic state variable member 40 and the magnetic sensing unit of the magnetic detector element are magnetically coupled). FIG. 2-4 is a diagram illustrating a state before a measurement magnetic field is applied to a variable magnetic field detection unit (the magnetic state of the magnetic state variable member is in a first state) included in the magnetic sensor according to Example 2-2. FIG. 2-5 is a diagram illustrating a state before a measurement magnetic field is applied to a variable magnetic field detection unit (the magnetic state of the magnetic state variable member is in a second state) included in the magnetic sensor according to Example 2-2. 10 is a diagram illustrating a state in which a measurement magnetic field is applied to a variable magnetic field detection unit (the magnetic state of the magnetic state variable member is in the second state) provided in the magnetic sensor according to Example 2-2. FIG.FIG. is a diagram for explaining a state before a measurement magnetic field is applied to a variable magnetic field detection unit included in a magnetic sensor according to an embodiment (Embodiment 3-1) in which the variable magnetic field detection unit is of type C and has a configuration of the first embodiment (the magnetically variable member 40 and the magnetosensitive portion of the magnetic detection element are magnetically uncoupled), and the magnetic state of the magnetically variable member is in the first state. FIG. is a diagram for explaining a state in which a measurement magnetic field is applied to a variable magnetic field detection unit included in a magnetic sensor according to Embodiment 3-1, and the magnetic state of the magnetically variable member is in the first state. FIG. is a diagram for explaining a state before a measurement magnetic field is applied to a variable magnetic field detection unit included in a magnetic sensor according to Embodiment 3-1, and the magnetic state of the magnetically variable member is in the second state. FIG. is a diagram for explaining a state in which a measurement magnetic field is applied to a variable magnetic field detection unit included in a magnetic sensor according to Embodiment 3-1, and the magnetic state of the magnetically variable member is in the second state. FIG. is a diagram for explaining a state before a measurement magnetic field is applied to a variable magnetic field detection unit included in a magnetic sensor according to an embodiment (Embodiment 3-2) in which the variable magnetic field detection unit is of type C and has a configuration of the second embodiment (the magnetically variable member 40 and the magnetosensitive portion of the magnetic detection element are magnetically coupled), and the magnetic state of the magnetically variable member is in the first state. FIG. is a diagram for explaining a state in which a measurement magnetic field is applied to a variable magnetic field detection unit included in a magnetic sensor according to Embodiment 3-2, and the magnetic state of the magnetically variable member is in the first state. FIG. is a diagram for explaining a state before a measurement magnetic field is applied to a variable magnetic field detection unit included in a magnetic sensor according to Embodiment 3-2, and the magnetic state of the magnetically variable member is in the second state. FIG. is a diagram for explaining a state in which a measurement magnetic field is applied to a variable magnetic field detection unit included in a magnetic sensor according to Embodiment 3-2, and the magnetic state of the magnetically variable member is in the second state. FIG. is a diagram for explaining a state in which a measurement magnetic field is applied to a variable magnetic field detection unit included in a magnetic sensor according to a modification of Embodiment 2-1, and the magnetic state of the magnetically variable member is in the first state.

[0041] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In each drawing, the same members are denoted by the same reference numerals, and the description thereof will be omitted. In order to show the positional relationship of each member, reference coordinates are shown in each drawing as appropriate.

[0042] Fig. 1 is a block diagram of a magnetic sensor according to one embodiment of the present invention. Fig. 2 is an explanatory diagram of a magnetic field detection unit provided in the magnetic sensor according to one embodiment of the present invention. The magnetic sensor 1 of this embodiment includes a magnetic field detection unit 2, a control power supply 3, a magnetic field calculation unit 4, an amplifier 5, an analog-to-digital conversion circuit (A / D conversion circuit 6), and a control unit 7. The control unit 7 controls the various units that make up the magnetic sensor 1, and is configured as a CPU (central processing unit), a program, etc.

[0043] The magnetic field detection unit 2 detects an external magnetic field as a measurement target. As shown in FIG. 2 , the magnetic field detection unit 2 is configured with a full bridge circuit 15 configured with magnetic sensor elements 10a, 10b, 10c, and 10d that measure a magnetic field along the X direction. In this embodiment, the magnetic field detection unit 2 has variable magnetic field detection units 100a, 100b, 100c, and 100d corresponding to the magnetic sensor elements 10a, 10b, 10c, and 10d, respectively. The control power supply 3 applies a predetermined current or a predetermined voltage to each unit based on a control signal from the control unit 7.

[0044] The magnetic field calculation unit 4 calculates the external magnetic field to be measured (measured magnetic field H) based on the output of the magnetic field detection unit 2, and is configured, for example, with a CDS (Correlated Double Sampling) circuit. The magnetic field calculation unit 4 calculates the measured magnetic field H based on a first output from the variable magnetic field detection units 100a, 100b, 100c, and 100d when the magnetic state of the magnetic state variable member 40 (described later) is in a first state, and a second output from the variable magnetic field detection units 100a, 100b, 100c, and 100d when the magnetic state of the magnetic state variable member 40 is in a second state. For example, 1 / f noise can be removed from the first output by calculating the difference between a signal based on the first output and a signal based on the second output.

[0045] In the magnetic sensor 1, after the magnetic field calculation unit 4 calculates the measured magnetic field H, the signal corresponding to the calculated measured magnetic field H is amplified by the amplifier 5 and then converted into digital data by the A / D conversion circuit 6.

[0046] The four magnetic sensor elements 10a, 10b, 10c, and 10d included in the magnetic field detection unit 2 of the magnetic sensor 1 according to one embodiment of the present invention may be provided on the same substrate (one chip). In this embodiment, the four magnetic sensor elements 10a, 10b, 10c, and 10d are provided on the same substrate (not shown), and FIG. 2 is a view of the magnetic field detection unit 2 of the magnetic sensor 1 as viewed from the stacking surface (front surface) of the substrate in the normal direction of the substrate. That is, in FIG. 2, the Z1 side is the front surface of the substrate, and the Z2 side is the back surface of the substrate. The Z direction is along the stacking direction of the magnetic sensor elements 10a, 10b, 10c, and 10d.

[0047] The magnetic field detection unit 2 has a full bridge circuit 15 in which a first half bridge circuit, in which magnetic detector elements 10a and 10b, both of which extend in the Y direction, are connected in series, and a second half bridge circuit, in which magnetic detector elements 10c and 10d, both of which extend in the Y direction, are connected in series, are connected in parallel between a power supply terminal Vdd, which is a power supply feeding point, and a ground terminal GND.

[0048] The first half-bridge circuit has an output terminal V1 between the magnetic detector element 10a and the magnetic detector element 10b. The second half-bridge circuit has an output terminal V2 between the magnetic detector element 10c and the magnetic detector element 10d. The potential difference between the outputs from these two output terminals V1 and V2 (midpoint potential Va of the first half-bridge circuit - midpoint potential Vb of the second half-bridge circuit) allows quantitative measurement of the magnitude of the external magnetic field applied from the outside as the measured magnetic field H. In this embodiment, the magnetic field detection unit 2 outputs a first signal including the midpoint potential Va from the output terminal V1 and a second signal including the midpoint potential Vb from the output terminal V2. The processing performed by the magnetic field calculation unit 4 includes calculating the midpoint potential difference using these first and second signals as inputs.

[0049] In the pair of magnetic detector elements 10a and 10b forming the first half-bridge circuit, the magnetization 11m of the pinned magnetic layer 11 (see FIG. 3A) is oriented in the X2 direction and the X1 direction, in that order, as indicated by the hollow arrows in FIG. 2. In the pair of magnetic detector elements 10c and 10d forming the second half-bridge circuit, the magnetization 11m of the pinned magnetic layer 11 is oriented in the X1 direction and the X2 direction, in that order, as indicated by the hollow arrows in FIG. 2.

[0050] In the first half-bridge circuit and the second half-bridge circuit, the magnetization 11m of the fixed magnetic layer 11 of the magnetic detector element 10b on the power supply terminal Vdd side and the magnetic detector element 10d is opposite (anti-parallel). The magnetization 11m of the fixed magnetic layer 11 of the magnetic detector element 10a on the ground terminal GND side and the magnetic detector element 10c is opposite (anti-parallel). Therefore, the sensitivity axis direction of the magnetic detector elements 10a, 10b, 10c, and 10d is the X direction, which is also referred to as the "first direction" in this specification. The Z direction is also referred to as the "second direction," and the Y direction is also referred to as the "third direction."

[0051] The four magnetic detector elements 10a, 10b, 10c, and 10d have the same orientation of magnetization 13m of the free magnetic layer 13 (see FIG. 3A) when no measurement magnetic field H is applied, and are aligned along the Y direction Y2 direction (hereinafter abbreviated as "Y2 direction"; the same applies to other directions) as indicated by the black arrows in FIG. 2. The method for aligning the orientation of magnetization 13m of the free magnetic layer 13 when no measurement magnetic field H is applied is not limited. An external bias magnetic field may be applied, or exchange coupling with an antiferromagnetic layer that interacts with the free magnetic layer 13 may be used.

[0052] With the above-described configuration, the outputs of the output terminal V1 from the first half-bridge circuit and the output terminal V2 from the second half-bridge circuit change in opposite directions as the magnitude of the measured magnetic field H in the X direction changes. Therefore, a large output is obtained as the potential difference between the two output terminals V1 and V2. Therefore, the magnetic sensor 1 can detect the measured magnetic field H with high accuracy. Note that the first or second half-bridge circuit can be used instead of the full-bridge circuit 15, or the magnetic sensor element 10a can be used alone.

[0053] 2, the magnetic sensor 1 according to this embodiment includes variable magnetic field detection units 100a, 100b, 100c, and 100d that correspond to the magnetic detection elements 10a, 10b, 10c, and 10d, respectively, and measure the measurement magnetic field H by changing the surrounding magnetic environment. Below, the variable magnetic field detection unit 100a will be described as a specific example.

[0054] 3A is a diagram illustrating a variable magnetic field detection unit (the magnetic state of the magnetic state variable member is in a first state) included in a magnetic sensor according to a first embodiment of the present invention. The variable magnetic field detection unit 100a includes a first magnetic body 31 and a second magnetic body 32 that are magnetized by a measurement magnetic field H along a first direction, a magnetic detection element 10a located between the first magnetic body 31 and the second magnetic body 32 in the first direction, a magnetic state variable member 40 whose magnetic state is changeable, and a magnetic state modulation member 20 that changes the magnetic state of the magnetic state variable member 40. In this specification, the concept of "magnetization" used with respect to a magnetic member such as the magnetic state variable member 40 also includes the generation of a magnetic field inside the member based on a physical phenomenon different from the magnetization of a ferromagnetic body (for example, a virtual magnetic field generated based on the topological properties of an antiferromagnetic body).

[0055] The first magnetic body 31 and the second magnetic body 32 may be made of any material as long as they can be magnetized in the first direction by the measurement magnetic field H along the first direction. Specific examples include magnetic materials such as a CoFe alloy and a NiFe alloy (nickel-iron alloy). The first magnetic body 31 and the second magnetic body 32 function as magnetic collectors (yokes) that collect and magnetize the measurement magnetic field H in the first direction. As shown in FIG. 3A , when the measurement magnetic field H is oriented toward one side of the first direction, specifically the X1 direction, the measurement magnetic field H is collected by the first magnetic body 31 and magnetizes the first magnetic body 31. As a result, a magnetic flux (hereinafter also referred to as "measurement magnetic flux Φ") with a density higher than that of the measurement magnetic field H is generated in the first magnetic body 31. This measurement magnetic flux Φ is emitted in the first direction from the first end 311, which is the end of the first magnetic body 31 on the first orientation side (X1 side). The magnetic permeability μ0 of the insulator 50 made of the first material and located around the first magnetic body 31 and the second magnetic body 32 is sufficiently lower than the magnetic permeability of the first magnetic body 31 and the second magnetic body 32, so the measurement magnetic flux Φ emitted in the first direction from the first end 311 also diffuses in the second and third directions within the first material, but converges to the end of the second magnetic body 32 on the X2 side.

[0056] The magnetic sensor element 10a is located in a first orientation relative to a first end 311, which is the end of the first magnetic body 31 on the first orientation side (X1 side), and has a sensitivity axis along the first direction. Specific examples of the magnetic sensor element 10a include magnetoresistive elements such as giant magnetoresistive (GMR) elements and tunneling magnetoresistive (TMR) elements, and Hall elements. FIG. 3A shows a giant magnetoresistive (GMR) element as a specific example of the magnetic sensor element 10a. The magnetic sensor element 10a is located between the first magnetic body 31 and the second magnetic body 32. In other words, the second magnetic body 32 is located more distal in the first direction (X direction) than the magnetic sensor element 10a when viewed from the first end 311 of the first magnetic body 31. The first magnetic body 31 and the second magnetic body 32 collect the measurement magnetic field H in the first direction (X direction) and increase the magnetic flux density between the first magnetic body 31 and the second magnetic body 32, so that the magnetic detection element 10a has higher magnetic resolution than when the first magnetic body 31 and the second magnetic body 32 are not provided.

[0057] The magnetic sensor element 10a, which is a giant magnetoresistance effect element, includes a pinned magnetic layer 11, a free magnetic layer 13, and an intermediate layer 12 formed between the pinned magnetic layer 11 and the free magnetic layer 13. The pinned magnetic layer 11 is made of a magnetic material such as a CoFe alloy (cobalt-iron alloy). The intermediate layer 12 is made of a non-magnetic material such as Cu. The free magnetic layer 13 is made of a soft magnetic material such as a CoFe alloy or a NiFe alloy (nickel-iron alloy) and is formed as a single-layer structure, a laminated structure, a laminated ferrimagnetic structure, or the like. When the magnetic sensor element 10a is made of a tunnel magnetoresistance effect element, the intermediate layer 12 is an insulating barrier layer made of MgO, Al2O3, titanium oxide, or the like.

[0058] The resistance value of the magnetic detector element 10a changes depending on the relative relationship between the magnetization directions of the fixed magnetic layer 11, in which the direction of magnetization 11m is fixed, and the free magnetic layer 13, which is a magnetically sensitive part whose direction and magnitude of magnetization 13m change in response to an external magnetic field. The variable magnetic field detector 100a of the magnetic sensor 1 can measure the direction and strength of an external magnetic field based on changes in the resistance value of the magnetic detector element 10a. In this embodiment, the free magnetic layer 13 is located on the Z2 side of the magnetic detector element 10a, and the detection center 10P of the magnetic detector element 10a is located at the center of the free magnetic layer 13.

[0059] The magnetic state variable member 40 is a member that can be in a first state and a second state, which differ in magnetic state including at least one of effective magnetic permeability and orientation of magnetization 40m, and the magnetic state is controlled by the magnetic state modulating member 20. The magnetic state variable member 40 is located closer to the first orientation (X1 side) than the first end 311 of the first magnetic body 31, and in the example shown in Fig. 3A, is located between the first magnetic body 31 and the second magnetic body 32 in the first direction.

[0060] Although the relative permeability of the magnetic state changeable member 40, which is made of an antiferromagnetic material, is approximately 1 or less, as described above, a magnetic field stronger than the external magnetic field may be generated inside the magnetic state changeable member 40. In this case, the magnetic state changeable member 40 generates a magnetic collection phenomenon that collects the external magnetic field within itself. However, due to its antiferromagnetic properties, the magnetic field generated inside the magnetic state changeable member 40 does not leak to components that are not magnetically coupled to the magnetic state changeable member 40. Therefore, in this specification, the "effective magnetic permeability" of the magnetic state changeable member 40 is evaluated based on its magnetic collection function when subjected to an external magnetic field in a predetermined direction. For example, if the relative permeability around the magnetic state changeable member 40 is 1, and the magnetic state changeable member 40 has the function of further collecting the external magnetic field when subjected to an external magnetic field having a component along a first direction, the effective relative permeability of the magnetic state changeable member 40 in the first direction is determined to be greater than 1. Therefore, when the effective relative permeability of the magnetic state changeable member 40 in the first direction exceeds 1 as described above, the magnetic flux density around the magnetic state changeable member 40 decreases due to the magnetic flux collecting function of the magnetic state changeable member 40.

[0061] In one specific example, the magnetic state variable member 40 has an effective magnetic permeability μ2 in the first direction (X direction) in the second state that is higher than the effective magnetic permeability μ1 in the first direction (X direction) in the first state. Also, the effective magnetic permeability μ2 in the first direction (X direction) in the second state is higher than the magnetic permeability μ0 in the first direction (X direction) of the first material located between the first magnetic body 31 and the magnetic detection element 10a. In this embodiment, an insulator 50 is located as the first material.

[0062] In the first embodiment, the magnetic state variable member 40 and the magnetic state modulation member 20 are stacked in the second direction (Z direction) to form the magnetic control body 60, and a non-magnetic member 41 is provided between the magnetic control body 60 and the magnetic detection element 10a, and the non-magnetic member 41 magnetically decouples the magnetic state variable member 40 of the magnetic control body 60 from the free magnetic layer 13 of the magnetic detection element 10a.

[0063] 3A , the measurement magnetic field H is collected by the first magnetic body 31, which functions as a yoke. This magnetic field magnetizes the first magnetic body 31, causing a measurement magnetic flux Φ to be emitted from the first end 311 of the first magnetic body 31. In the first state, the effective permeability μ1 of the magnetic state variable member 40 in the X direction is not significantly different from the permeability μ0 of the insulator 50. Therefore, the measurement magnetic flux Φ is emitted from the first end 311 of the first magnetic body 31 while diffusing to include components in the second direction (Z direction) and the third direction (Y direction) as well as components in the X1 direction. The measurement magnetic flux Φ then converges between the first magnetic body 31 and the second magnetic body 32, with the components in the second direction and the third direction becoming smaller, and reaches the second magnetic body 32, which is located closer to the X1 side than the first magnetic body 31. A part of the measurement magnetic flux Φ that diffuses and converges in this way reaches the free magnetic layer 13 of the magnetic sensor element 10a and is measured by the magnetic sensor element 10a.

[0064] (Second State) FIG. 3B is a diagram illustrating the variable magnetic field detection unit included in the magnetic sensor according to the first embodiment of the present invention (the magnetic state of the magnetic state changeable member is in the second state). In the second state, the effective permeability μ2 of the magnetic state changeable member 40 in the X direction is higher than the permeability μ0 of the insulator 50. Therefore, the measurement magnetic flux Φ emitted from the first end 311 preferentially passes through the magnetic state changeable member 40. Due to the concentration of this measurement magnetic flux Φ on the magnetic state changeable member 40, the density of the measurement magnetic flux Φ reaching the free magnetic layer 13 decreases compared to the first state. As a result, the measurement sensitivity of the magnetic sensor element 10a located near the magnetic state changeable member 40 to the measurement magnetic flux Φ decreases. Therefore, the second output from the variable magnetic field detection unit in the second state is equal in noise signal strength to the first output in the first state, but the signal strength based on the measurement magnetic flux Φ decreases. Note that FIG. 3B illustrates a case in which the magnetic state changeable member 40 is made of an antiferromagnetic material. Therefore, the measurement magnetic flux Φ that enters the magnetic state changeable member 40 from the first magnetic body 31 does not leak out from the magnetic state changeable member 40. When the magnetic state changeable member 40 is made of a ferromagnetic body, the magnetic flux based on the measurement magnetic flux Φ at the X1 side end of the magnetic state changeable member 40 passes through the second magnetic body 32 and is emitted from the X1 side of the second magnetic body 32.

[0065] FIG. 4 is a flowchart illustrating a magnetic measurement method using a magnetic sensor according to the first embodiment of the present invention. As shown in FIG. 4 , in a first measurement step, a control signal is output from the control power supply 3 to set the magnetic state of the magnetic state variable member 40 in each of the variable magnetic field detectors 100a-100d included in the magnetic field detector 2 to a first state. Measurements are then performed using the magnetic detector elements 10a, 10b, 10c, and 10d with the magnetic state variable member 40 in the first state, and first outputs are obtained from each of the variable magnetic field detectors 100a, 100b, 100c, and 100d. These signals cause the magnetic field detector 2 to output a first signal (a signal including the midpoint potential Va from the output terminal V1) and a second signal (a signal including the midpoint potential Vb from the output terminal V2) (step S101). These two signals output from the magnetic field detection unit 2 are input to the magnetic field calculation unit 4, and are stored in the magnetic field calculation unit 4 or in a memory not shown, either as these signals or as a midpoint potential difference signal, which is the difference between the two signals.

[0066] Next, in a second measurement step, a control signal is output from the control power supply 3 to the control unit 7, and a signal is output to change the magnetic state of the magnetic state changeable member 40 of each of the variable magnetic field detectors 100a, 100b, 100c, and 100d of the magnetic field detector 2 to a second state. With the magnetic state changeable member 40 in the second state, measurements are performed using the magnetic detector elements 10a, 10b, 10c, and 10d, and second outputs are obtained from each of the variable magnetic field detectors 100a, 100b, 100c, and 100d. These signals cause the magnetic field detector 2 to output a first signal and a second signal (step S102). The measurement times in steps S101 and S102 are both significantly shorter than 1 second (e.g., 0.3 seconds), and the times required for steps S101 and S102 are also significantly shorter than 1 second (e.g., 0.7 seconds). Therefore, steps S101 and S102 are performed in an environment in which the 1 / f noise is substantially equal, and the 1 / f noise contained in the first output and the 1 / f noise contained in the second output are substantially equal. The two signals output from the magnetic field detection unit 2 are input to the magnetic field calculation unit 4, and stored in the magnetic field calculation unit 4 or in a memory (not shown) either as they are or as a midpoint potential difference signal, which is the difference between the two signals.

[0067] Next, the magnetic field calculation unit 4 performs a process (step S103) to calculate the difference between the signal based on the first output (a signal including the midpoint potential difference in the first state) and the signal based on the second output (a signal including the midpoint potential difference in the second state) stored in the magnetic field calculation unit 4 or a memory (not shown) in steps S101 and S102. If the signals stored in the magnetic field calculation unit 4 or a memory (not shown) are the first and second signals before the midpoint potential difference is calculated, the magnetic field calculation unit 4 performs a process to calculate the difference between the first and second signals in the first state to obtain a signal including the midpoint potential difference in the first state, and a process to calculate the difference between the first and second signals in the second state to obtain a signal including the midpoint potential difference in the second state, and then performs a process to calculate the difference between these two signals including the midpoint potential difference. By performing the above process, the magnetic field calculation unit 4 obtains a measurement signal from which 1 / f noise has been appropriately removed. The measurement signal is amplified by the amplifier 5 and converted into a digital signal by the A / D conversion circuit 6. Therefore, the measurement signal obtained by the magnetic measurement method using the magnetic sensor 1 of this embodiment has 1 / f noise properly removed, and therefore the resolution (magnetic resolution) of the signal based on the measured magnetic flux Φ is higher than that of the signal based on the first output (signal including the midpoint potential difference in the first state) or the signal based on the second output (signal including the midpoint potential difference in the second state).

[0068] In this embodiment, since the magnetic field detection unit 2 has the full bridge circuit 15, the signals to be processed to find the difference in the magnetic field calculation unit 4 are the signal of the midpoint potential difference in the first state based on the first output and the signal of the midpoint potential difference in the second state based on the second output, but the signals to be processed by the magnetic field calculation unit 4 are set appropriately depending on the output signal from the magnetic field detection unit 2. For example, if the magnetic field detection unit 2 has only one variable magnetic field detection unit 100a, the magnetic field calculation unit 4 will find the difference between the first signal and the second signal from the variable magnetic field detection unit 100a.

[0069] (Arrangement) It is preferable that the arrangement of the magnetic detector element 10a and the magnetic state variable member 40 is set so that the degree of difference between the signal based on the measured magnetic flux Φ included in the first output and the signal based on the measured magnetic flux Φ included in the second output becomes large.

[0070] From this perspective, the magnetic detector element 10a and the magnetic state variable member 40 may be aligned in a second direction (Z direction) perpendicular to the first direction (X direction). In this arrangement, a change in the magnetic state of the magnetic state variable member 40 is likely to appear as a change in the strength of the measured magnetic flux Φ reaching the detection center 10P of the magnetic detector element 10a.

[0071] It is preferable that the magnetic state changeable member 40 has a portion closer to the first magnetic body 31 in the first direction (X direction) than the detection center 10P of the magnetic detector element 10a. With this arrangement, in the second state, the measurement magnetic flux Φ emitted from the first end 311 easily reaches the magnetic state changeable member 40 that is relatively closer in the first direction, so that the magnetic flux is efficiently concentrated on the magnetic state changeable member 40 in the second state. From this perspective, it is preferable that the length of the magnetic state changeable member 40 in the first direction be longer than the length of the magnetic detector element 10a in the first direction (X direction).

[0072] The center of the magnetic state variable member 40 in the first direction (X direction) and the detection center 10P of the magnetic detector element 10a are preferably located at the same position in the first direction (X direction). With this arrangement, the magnetic flux in the first direction (X direction) that the magnetic state variable member 40 in the first state can exert on the magnetic detector element 10a is likely to be equal to the magnetic flux in the first direction that the magnetic state variable member 40 in the second state can exert on the magnetic detector element 10a. This increases the correlation between the noise signals included in the first output and the noise signals included in the second output, which is expected to improve the noise removal efficiency of the measurement signal obtained by the magnetic field calculation unit 4. From the perspective of consistently improving the noise removal efficiency of the measurement signal and improving the operational stability of the magnetic state variable member 40, it may be preferable for the center of the magnetic state variable member 40 and the center of the magnetic state modulation member 20 to be equal in the first direction (X direction).

[0073] The length of the magnetic state variable member 40 in the first direction (X direction) is preferably longer than the length of the magnetic detector element 10a in the first direction (X direction). In this arrangement, a part of the X2 side of the magnetic state variable member 40 is located between the first end 311 and the magnetic detector element 10a in the first direction (X direction), and therefore the magnetic flux density reaching the magnetic detector element 10a is easily affected by the magnetic state of the magnetic state variable member 40.

[0074] From the viewpoint of more stably realizing that the magnetic flux density reaching the magnetic detector element 10a is more susceptible to the magnetic state of the magnetic state variable member 40, it is preferable that the magnetic state variable member 40 be arranged so that the first magnetic body 31 and the second magnetic body 32 are magnetically coupled in the second state. FIG. 5 is an explanatory diagram of a preferred example of a variable magnetic field detection unit included in the magnetic sensor according to the first embodiment of the present invention. In the example shown in FIG. 5, when viewed from the second direction (Z direction), the magnetic state variable member 40 is arranged so that it is magnetically coupled to the first magnetic body 31 and the second magnetic body 32 in the second state. Specifically, the magnetic state variable member 40 has a portion overlapping with the first magnetic body 31 and a portion overlapping with the second magnetic body 32. 5, the measurement magnetic flux Φ generated by magnetization of the first magnetic body 31 flows almost directly from the magnetic coupling portion between the magnetic state changeable member 40 and the first magnetic body 31 into the magnetic state changeable member 40 in the second state, and flows out almost directly from the magnetic coupling portion between the magnetic state changeable member 40 and the first magnetic body 31 to the second magnetic body 32. Therefore, the measurement magnetic flux Φ does not substantially contain a component that reaches the magnetic detector element 10a, and only noise signals tend to be measured by the magnetic detector element 10a.

[0075] FIG. 6 is an explanatory diagram of another preferred example of a variable magnetic field detection unit included in the magnetic sensor according to the first embodiment of the present invention. In the configuration shown in FIG. 6 , the arrangement of the components of the magnetic sensor element 10a is reversed in the Z direction compared to the configuration shown in FIG. 5 . That is, in FIG. 5 , the free magnetic layer 13 of the magnetic sensor element 10a is located closer to the magnetic control element 60 (Z2 side), whereas in FIG. 6 , the fixed magnetic layer 11 of the magnetic sensor element 10a is located closer to the magnetic control element 60 (Z2 side). Therefore, in the configuration shown in FIG. 6 , the detection center 10P of the magnetic sensor element 10a is closer to the center of the first magnetic body 31 and the second magnetic body 32 in the second direction (Z direction) than in the configuration shown in FIG. 5 . Therefore, it is expected that the intensity of the X1-direction component of the measurement magnetic flux Φ reaching the detection center 10P of the magnetic sensor element 10a in the first state will be relatively high.

[0076] FIG. 7 is an explanatory diagram of another preferred example of the variable magnetic field detection unit included in the magnetic sensor according to the first embodiment of the present invention. In the configuration shown in FIG. 7 , the positional relationship between the magnetic detector element 10a and the magnetic control body 60 in the second direction (Z direction) is reversed compared to the configuration shown in FIG. 5 . That is, in FIG. 5 , the magnetic detector element 10a is located closer to the Z1 side than the magnetic control body 60, whereas in FIG. 7 , the magnetic detector element 10a is located closer to the Z2 side than the magnetic control body 60. Therefore, in the configuration shown in FIG. 7 , the detection center 10P of the magnetic detector element 10a is farther from the center of the first magnetic body 31 and the second magnetic body 32 in the second direction (Z direction) than in the configuration shown in FIG. 5 . Therefore, in the second state, the intensity of the measurement magnetic flux Φ reaching the detection center 10P of the magnetic detector element 10a is expected to be particularly low. Furthermore, because the magnetic detector element 10a is located behind the magnetic control body 60 when viewed from the first end 311, even if part of the measurement magnetic flux Φ is emitted from the first end 311 to the insulator 50, the magnetic control body 60 acts as a magnetic shield, making it difficult for the magnetic flux to reach the magnetic detector element 10a. Therefore, in the second state, only noise signals are likely to be measured by the magnetic detector element 10a.

[0077] 8 is an explanatory diagram of a modified example of the variable magnetic field detection unit included in the magnetic sensor according to the first embodiment of the present invention. When the direction of the measurement magnetic field H is limited to one direction, one of the first magnetic body 31 and the second magnetic body 32 can be omitted. For example, when the direction of the measurement magnetic field H is limited to the first direction, as shown in FIG. 8, even if the second magnetic body 32 is omitted, it is possible to stably prevent the measurement magnetic flux Φ from reaching the detection center 10P of the magnetic detection element 10a in the second state. Note that FIG. 8 shows a case where the magnetic state variable member 40 is made of an antiferromagnetic material.

[0078] When the measurement magnetic field H is a magnetic field in the first direction (X direction), it is preferable that the length of the first magnetic body 31 in the first direction (X direction) is longer than the length in the second direction (Z direction). When the length relationship is reversed (length in the first direction < length in the second direction), there is a higher possibility of detecting a magnetic field in the second direction (Z direction).

[0079] Second Embodiment Fig. 9 is a diagram illustrating a variable magnetic field detection unit provided in a magnetic sensor according to a second embodiment of the present invention (the magnetic state of the magnetic state variable member is in the second state). In contrast to the first embodiment, the second embodiment does not include a non-magnetic member 41, and the magnetic state variable member 40 and the free magnetic layer 13 are magnetically coupled. Therefore, in the second embodiment, the magnetic state variable member 40 essentially functions as the free magnetic layer 13. Therefore, in the second state, the detection sensitivity of the magnetic detection element 10a is directly affected by the magnetic state of the magnetic state variable member 40.

[0080] For example, in the second state, the effective permeability μ2 of the magnetic state changeable member 40 in the first direction is higher than the permeability μ0 of the surrounding insulator 50, and therefore the measurement magnetic flux Φ is preferentially concentrated in the magnetic state changeable member 40, as shown in Fig. 9. In this case, part of the measurement magnetic flux Φ that is magnetized in the magnetic state changeable member 40 and travels in the X1 direction also passes through the free magnetic layer 13 that is magnetically coupled to the magnetic state changeable member 40, and its direction has a component in the X1 direction. Therefore, in the second embodiment, the intensity of the measurement magnetic flux Φ that reaches the free magnetic layer 13 may be higher in the second state than in the first state.

[0081] In contrast, in the first state, the effective permeability μ1 in the first direction of the magnetic state changeable member 40 is equivalent to the permeability μ0 of the surrounding insulator 50, so the degree of collection of the measurement magnetic flux Φ by the magnetic state changeable member 40 is lower than in the second state. Therefore, even if the measurement magnetic flux Φ reaches the free magnetic layer 13 magnetically coupled to the magnetic state changeable member 40, the magnetic flux density thereof will be lower than in the second state.

[0082] Thus, in the second embodiment, the measurement magnetic flux Φ is more likely to reach the free magnetic layer 13 in the second state than in the first state. Therefore, in the second embodiment, a measurement signal from which noise signals have been removed can be obtained by subtracting the first output obtained in the first state from the second output obtained in the second state.

[0083] In the second embodiment, the magnetic state changeable member 40 and the free magnetic layer 13 are magnetically coupled, so the magnetic state changeable member 40 and the free magnetic layer 13 may be made of the same material, with one member (the variable free magnetic layer) fulfilling the functions of both the magnetic state changeable member 40 and the free magnetic layer 13. In this case, the intermediate layer 12 and the fixed magnetic layer 11 may be laminated on part of the surface of the variable free magnetic layer facing the Z1 side, thereby constituting the magnetic detection element 10a having the structure of a magnetoresistive effect element. The variable free magnetic layer may be made of the same material as the material constituting the magnetic state changeable member 40. Therefore, the term "magnetization" used with respect to the variable free magnetic layer has a broader meaning than the magnetization of a ferromagnetic material and includes, for example, a virtual magnetic field based on the topological properties of an antiferromagnetic material.

[0084] 10 is a diagram illustrating a preferred example of a variable magnetic field detection unit (the magnetic state of the magnetic state variable member is in the second state) included in the magnetic sensor according to the second embodiment of the present invention. In the example shown in FIG. 10, similar to the example shown in FIG. 5, in the second state, the magnetic state variable member 40 is magnetically coupled to the first magnetic body 31 and the second magnetic body 32. Therefore, in the second state, the free magnetic layer 13 is magnetically coupled to the first magnetic body 31 and the second magnetic body 32. Therefore, in the second state, the measurement magnetic flux Φ reaches the free magnetic layer 13 particularly efficiently.

[0085] In the variable magnetic field detection unit 100a of the magnetic sensor 1 according to the embodiment of the present invention, the density of the measurement magnetic flux Φ that reaches the free magnetic layer 13 differs between a first state in which the effective magnetic permeability of the magnetic state variable member 40 in the first direction is relatively low and a second state in which the effective magnetic permeability is relatively high. Whether the state in which the measurement magnetic flux Φ that reaches the free magnetic layer 13 is relatively high is the first state or the second state is determined by the specific configuration.

[0086] Below, the detailed operation of the variable magnetic field detection unit 100a will be explained using as specific examples three configurations: a configuration (Type A) in which current is passed through the magnetic state modulation member 20 along the third direction (Y direction) to magnetize the magnetic state modulation member 20 in the third direction (Y direction), a configuration (Type B) in which current is passed through the magnetic state modulation member 20 along the first direction (X direction) to magnetize the magnetic state modulation member 20 in the third direction (Y direction), and a configuration (Type C) in which current is passed through the magnetic state modulation member 20 along the third direction (Y direction) to magnetize the magnetic state modulation member 20 in the second direction (Z direction), all of which share the same configuration in which current is passed through the magnetic state modulation member 20 to apply a spin orbit torque to the magnetic state variable member 40 and magnetize the magnetic state variable member 40 in a predetermined direction.

[0087] (Example 1-1) Figure 11A is a diagram illustrating the state before a measurement magnetic field is applied to a variable magnetic field detection unit (the magnetic state of the magnetic state variable member is in a first state) provided in a magnetic sensor according to an example (Example 1-1) having a configuration in which the variable magnetic field detection unit is Type A and the first embodiment (the magnetic state variable member 40 and the magnetic sensing portion of the magnetic detector element are magnetically uncoupled). Figure 11B is a diagram illustrating the state after a measurement magnetic field is applied to a variable magnetic field detection unit (the magnetic state of the magnetic state variable member is in a first state) provided in the magnetic sensor according to Example 1-1. In the variable magnetic field detection unit 100a shown in Figures 11A and 11B, the first magnetic body 31, the second magnetic body 32, and the insulator 50 are omitted (the same applies below).

[0088] In Example 1-1, the magnetic state modulation member 20 has a spin torque generation unit that generates the spin Hall effect, the Rashba-Edelstein effect, or the like by passing a current through the magnetic state modulation member 20 in the XY in-plane direction, and applies a spin orbit torque to the magnetic state variable member 40. The magnetic state modulation member 20 may be a film-like body, the entire body of which may be composed of the spin torque generation unit. In the configuration shown in FIG. 11A, the magnetic state modulation member 20 is composed of the spin torque generation unit. Materials that constitute the spin torque generation unit include heavy metals (5d transition metals) with high specific gravity, such as Hf, Ta, W, Pt, and Ir among paramagnetic transition metals; topological insulators such as BiSb, BiSe, Bi2Se3, and Bi2Te3; Mn3X (X = Sn, Ge, Ga, Rh, Pt, Ir); Mn 1-x Tr x Examples include antiferromagnetic materials such as gamma-phase (Tr = Ni, Fe, Cu, Ru, Pd, Ir, Rh, Pd, Pt); half-Heusler alloy topological semimetals such as LuPtSb, LuPdBi, LuPtBi, ScPtBi, YAuPb, LaPtBi, CePtBi, ThPtPb, and LaAuPb, as well as mixed crystals thereof. The spin torque generation portion may be composed of a single-phase film or a laminated film. In the case of a laminated film, a boundary region may be formed between adjacent films.

[0089] The magnetic state variable member 40 is made of a material that can rotate the magnetization 40m of the magnetic state variable member 40 when subjected to spin orbit torque from the magnetic state modulation member 20. Examples of such materials include soft magnetic materials such as CoFe alloys and NiFe alloys (nickel-iron alloys), and antiferromagnetic materials such as Mn3X (X = Sn, Ge, Ga, Rh, Pt, Ir). The magnetic state variable member 40 may be made of a single-phase film or a laminated film. In the case of a laminated film, a boundary region may be formed between adjacent films.

[0090] The non-magnetic member 41 may be made of an organic material or an inorganic material. In the case of an inorganic material, it may be made of a conductive material such as Cu or Ru, or an insulating material such as an oxide or nitride. The non-magnetic member 41 may be integral with the insulator 50.

[0091] In the variable magnetic field detection unit 100a according to this example, the magnetic state modulation member 20 has an antiferromagnetic portion made of an antiferromagnetic material. As a specific example, the entire magnetic state modulation member 20 is made of an antiferromagnetic portion. Therefore, in the first state in which the magnetic state modulation member 20 is in a non-conductive state, the magnetization 40m of the magnetic state variable member 40 is oriented in the Z1 direction due to the exchange coupling 20af with the magnetic state modulation member 20 (antiferromagnetic portion). Because of the small thickness in the Z direction, rotation of the magnetization 40m is unlikely to occur. Therefore, the magnetization 40m of the magnetic state variable member 40 is essentially fixed in the Z1 direction, and the effective magnetic permeability in the X direction, which is the direction in which the measurement magnetic field H is applied, is low. Therefore, in the X direction, the effective magnetic permeability μ1 of the magnetic state variable member 40 is almost identical to the magnetic permeability μ0 of the surrounding insulator 50.

[0092] When a measurement magnetic field H is applied in this state, the measurement magnetic flux Φ does not concentrate on the magnetic state variable member 40. Therefore, as shown in Fig. 11B, a considerable amount of the measurement magnetic flux Φ reaches the free magnetic layer 13, and the magnetic detector element 10a measures this reaching magnetic flux.

[0093] 12A is a diagram illustrating a state before a measurement magnetic field is applied to a variable magnetic field detection unit (the magnetic state of the magnetic state variable member is in a second state) included in the magnetic sensor according to Example 1-1. FIG. 12B is a diagram illustrating a state after a measurement magnetic field is applied to a variable magnetic field detection unit (the magnetic state of the magnetic state variable member is in a second state) included in the magnetic sensor according to Example 1-1.

[0094] In the second state, a current 20c is passed through the magnetic state modulation member 20 in the Y direction, specifically the Y1 direction, to bring it into a conducting state. As a result, due to the spin Hall effect or the like, spins unevenly distributed in one direction in the X direction are accumulated on the Z1 side of the magnetic state modulation member 20 and injected into the magnetic state variable member 40. The angular momentum of the accumulated spins is directly transferred, causing a torque to act on the magnetization 40m of the magnetic state variable member 40, i.e., a spin orbit torque is generated, and the magnetization 40m is oriented in the Y2 direction.

[0095] At this time, the magnetization 40m of the magnetic state changeable member 40 is oriented in the in-plane direction of the XY plane (first plane) perpendicular to the thickness direction of the magnetic state changeable member 40, and therefore the magnetization 40m can be rotated in the XY plane by the measured magnetic flux Φ. That is, in the second state, the magnetic state changeable member 40 has an effective permeability μ2 in the X direction that is higher than the effective permeability μ1 in the X direction in the first state (μ2>μ1).

[0096] 12B, when a measurement magnetic field H is applied, the magnetization 40m of the magnetic state variable member 40 rotates along the measurement magnetic flux Φ and becomes oriented in the X1 direction, thereby giving the magnetic state variable member 40 a magnetic collecting function, and the measurement magnetic flux Φ is concentrated in the magnetic state variable member 40. In this way, the measurement magnetic flux Φ that reached the free magnetic layer 13 when the magnetic state variable member 20 was in a non-conductive state is concentrated in the magnetic state variable member 40 by applying a current 20c to the magnetic state variable member 20. Therefore, in the second state, the measurement magnetic flux Φ is less likely to reach the magnetic detection element 10a than in the first state.

[0097] Thus, in Example 1-1, since the measured magnetic flux Φ is more likely to reach the magnetic detector element 10a in the first state than in the second state, by subtracting the second output from the first output in the magnetic field calculation unit 4, a measurement signal in which 1 / f noise has been appropriately removed can be obtained.

[0098] (Example 1-2) Figure 13A is a diagram illustrating a state before a measurement magnetic field is applied to a variable magnetic field detection unit (the magnetic state of the magnetic state variable member is in a first state) included in a magnetic sensor according to an example (Example 1-2) having a configuration in which the variable magnetic field detection unit is Type A and the second embodiment (the magnetic state variable member 40 and the magnetic sensing unit of the magnetic detector element are magnetically coupled). Figure 13B is a diagram illustrating a state after a measurement magnetic field is applied to a variable magnetic field detection unit (the magnetic state of the magnetic state variable member is in a first state) included in a magnetic sensor according to Example 1-2. Figure 14A is a diagram illustrating a state before a measurement magnetic field is applied to a variable magnetic field detection unit (the magnetic state of the magnetic state variable member is in a second state) included in a magnetic sensor according to Example 1-2. Figure 14B is a diagram illustrating a state after a measurement magnetic field is applied to a variable magnetic field detection unit (the magnetic state of the magnetic state variable member is in a second state) included in a magnetic sensor according to Example 1-2.

[0099] The variable magnetic field detector 100a according to Example 1-2 differs from the variable magnetic field detector 100a according to Example 1-1 in that it does not have a non-magnetic member 41, but the other configurations are the same. Therefore, in the variable magnetic field detector 100a according to Example 1-2, the magnetic state variable member 40 and the free magnetic layer 13 are magnetically coupled. Therefore, as shown in FIG. 13A , in a first state, which is a non-energized state in which no current is applied to the magnetic state modulation member 20, the exchange coupling 20af between the portion of the magnetic state modulation member 20 made of an antiferromagnetic material and the magnetic state variable member 40 causes the magnetization 40m of the magnetic state variable member 40 and the magnetization 13m of the free magnetic layer 13 magnetically coupled to the magnetic state variable member 40 to be oriented in the Z1 direction.

[0100] Because the thickness of the free magnetic layer 13 in the Z direction is small, the magnetization 13m is unlikely to rotate. Therefore, the magnetization 40m of the magnetic state variable member 40 and the magnetization 13m of the free magnetic layer 13 are essentially fixed in the Z1 direction. In other words, the effective magnetic permeability in the X direction of the magnetic state variable member 40 and the free magnetic layer 13 is almost the same as the magnetic permeability μ0 of the surrounding insulator 50.

[0101] Even if a measurement magnetic flux Φ is received in this state, as shown in FIG. 13B, the magnetization 13m of the free magnetic layer 13 is unlikely to rotate along the X direction, which is the sensitivity axis direction, and therefore the measurement magnetic flux Φ is unlikely to be measured by the magnetic detection element 10a.

[0102] On the other hand, in a second state in which a current 20c in the Y1 direction is passed through the magnetic state modulation member 20, as in Example 1-1, spin injection from the magnetic state modulation member 20 to the magnetic state variable member 40 occurs, causing a spin orbit torque in the magnetic state variable member 40, and the magnetization 40m of the magnetic state variable member 40 is aligned in the Y2 direction, as shown in Fig. 14A. Because the magnetic state variable member 40 and the free magnetic layer 13 are magnetically coupled, the magnetization 13m of the free magnetic layer 13 is also aligned in the Y2 direction.

[0103] The directions of the magnetization 40m and the magnetization 13m are in the XY plane perpendicular to the thickness of the magnetic state changeable member 40 and the free magnetic layer 13, and therefore the direction of the magnetization 40m of the magnetic state changeable member 40 and the direction of the magnetization 13m of the free magnetic layer 13 can both be rotated in the XY plane by the measured magnetic flux Φ. That is, the magnetic state changeable member 40 and the free magnetic layer 13 are in a state where the effective magnetic permeability in the X direction is high.

[0104] 14B, when a measurement magnetic field H is applied in this state, the magnetization 40m of the magnetic state changeable member 40 rotates along the measurement magnetic flux Φ and becomes oriented in the X1 direction, which gives the magnetic state changeable member 40 a magnetic collection function and causes the measurement magnetic flux Φ to concentrate in the magnetic state changeable member 40. Here, because the magnetic state changeable member 40 is magnetically coupled to the free magnetic layer 13, the magnetic flux oriented in the X1 direction, which has a higher density than in the first state (FIG. 13B), reaches the free magnetic layer 13 under the influence of the magnetization 40m of the magnetic state changeable member 40.

[0105] In this way, in the second state of Example 1-2, when the measurement magnetic field H is applied, the free magnetic layer 13 is magnetized more strongly in the X1 direction than in the first state, so the measurement sensitivity of the measurement magnetic field H of the magnetic detection element 10a is relatively higher in the second state. Therefore, by subtracting the first output from the second output in the magnetic field calculation unit 4, it is possible to obtain a measurement signal from which 1 / f noise has been appropriately removed.

[0106] In Examples 1-1 and 1-2, in the first state, the magnetization 40m of the magnetic state variable member 40 is oriented in the Z1 direction due to the exchange coupling 20af with the magnetic state modulation member 20 serving as a bias magnetic field source. However, the bias magnetic field source that aligns the magnetization 40m of the magnetic state variable member 40 in a predetermined direction in the first state is not limited to this. The magnetization 40m of the magnetic state variable member 40 may be oriented in the Z direction using an induced magnetic field from a current-carrying coil or a magnetic field from a permanent magnet as a bias magnetic field. Even in such cases, in the second state, it is sufficient that the magnetization 40m of the magnetic state variable member 40 is oriented in the Y direction based on the application of current to the magnetic state modulation member 20. From the viewpoint of increasing the correlation between the noise components contained in the first signal and the noise components contained in the second signal, it may be preferable that there is no difference in the bias magnetic field from the bias magnetic field source between the first state and the second state.

[0107] (Example 2-1) Figure 15A is a diagram illustrating a state before a measurement magnetic field is applied to a variable magnetic field detection unit (the magnetic state of the magnetic state variable member is in a first state) included in a magnetic sensor according to an example (Example 2-1) having a configuration in which the variable magnetic field detection unit is Type B and the first embodiment (the magnetic state variable member 40 and the magnetic sensing unit of the magnetic detector element are magnetically uncoupled). Figure 15B is a diagram illustrating a state after a measurement magnetic field is applied to a variable magnetic field detection unit (the magnetic state of the magnetic state variable member is in a first state) included in a magnetic sensor according to Example 2-1. Figure 16A is a diagram illustrating a state before a measurement magnetic field is applied to a variable magnetic field detection unit (the magnetic state of the magnetic state variable member is in a second state) included in a magnetic sensor according to Example 2-1. Figure 16B is a diagram illustrating a state after a measurement magnetic field is applied to a variable magnetic field detection unit (the magnetic state of the magnetic state variable member is in a second state) included in a magnetic sensor according to Example 2-1.

[0108] The variable magnetic field detecting unit 100a according to Example 2-1 has a non-magnetic member 41, and the magnetic state variable member 40 and the free magnetic layer 13 are not magnetically coupled, similar to the variable magnetic field detecting unit 100a according to Example 1-1.

[0109] In the first state, a current 20c is passed through the magnetic state modulation member 20 in the X direction, specifically, the X1 direction, to place the magnetic state modulation member 20 in a conducting state. The application of current causes spin injection from the magnetic state modulation member 20 to the magnetic state variable member 40, which generates a spin orbit torque in the magnetic state variable member 40, as in Example 1-1, and as shown in FIG. 15A , the magnetization 40m of the magnetic state variable member 40 is strongly aligned in the Y2 direction. In the variable magnetic field detection unit 100a according to Example 2-1, a bias magnetic field source 21 made of a permanent magnet or the like is stacked on the Z2 side of the magnetic state modulation member 20. However, the magnetic field 21m generated by the bias magnetic field source 21 and the spin ignition torque generated by the magnetic state modulation member 20 are set so that the influence on the orientation of the magnetization 40m of the magnetic state variable member 40 is dominated by the spin ignition torque generated by the magnetic state modulation member 20 over the magnetic field 21m generated by the bias magnetic field source 21.

[0110] 15B , even if the measurement magnetic flux Φ is applied to the magnetic state changeable member 40, the magnetization 40m of the magnetic state changeable member 40 is unlikely to rotate along the X direction. That is, the magnetic state changeable member 40 has a low effective magnetic permeability μ1 in the X direction, which is equivalent to the magnetic permeability μ0 of the surrounding insulator 50. Therefore, the magnetic state changeable member 40 is unlikely to affect the measurement magnetic flux Φ that reaches the free magnetic layer 13 of the magnetic detector element 10a, and the magnetic detector element 10a measures the measurement magnetic flux Φ in a magnetic environment similar to that when the magnetic state changeable member 40 is not present (i.e., is replaced by the insulator 50).

[0111] On the other hand, in the second state, the application of the current 20c to the magnetic state modulation member 20 is stopped, resulting in a non-energized state. As a result, as shown in FIG. 16A , the magnetic state modulation member 20 no longer controls the direction of the magnetization 40m of the magnetic state variable member 40. Therefore, the magnetic field 21m generated by the bias magnetic field source 21 aligns the magnetization 40m of the magnetic state variable member 40 in the Y2 direction, but to a weaker extent than in the first state. Therefore, the effective magnetic permeability μ2 in the X direction of the magnetic state variable member 40 in the second state is higher than the magnetic permeability μ0 of the surrounding insulator 50.

[0112] 16B, when the measurement magnetic field H is applied in this state, the magnetization 40m of the magnetic state variable member 40 rotates along the measurement magnetic flux Φ and becomes oriented in the X1 direction, which causes the magnetic state variable member 40 to have a magnetic collecting function, and the measurement magnetic flux Φ is concentrated in the magnetic state variable member 40. As a result, the density of the measurement magnetic flux Φ that reaches the free magnetic layer 13 of the magnetic detector element 10a decreases, and the measurement sensitivity of the measurement magnetic field H in the variable magnetic field detector 100a decreases compared to the first state.

[0113] Thus, in Example 2-1, the measured magnetic flux Φ is more likely to reach the magnetic detector element 10a in the first state than in the second state, and therefore, by subtracting the second output from the first output in the magnetic field calculation unit 4, a measurement signal in which 1 / f noise has been appropriately removed can be obtained.

[0114] (Example 2-2) Figure 17A is a diagram illustrating a state before a measurement magnetic field is applied to a variable magnetic field detection unit (the magnetic state of the magnetic state variable member is in a first state) included in a magnetic sensor according to an example (Example 2-2) having a configuration in which the variable magnetic field detection unit is Type B and the second embodiment (the magnetic state variable member 40 and the magnetic sensing portion of the magnetic detector element are magnetically coupled). Figure 17B is a diagram illustrating a state after a measurement magnetic field is applied to a variable magnetic field detection unit (the magnetic state of the magnetic state variable member is in a first state) included in a magnetic sensor according to Example 2-2. Figure 18A is a diagram illustrating a state before a measurement magnetic field is applied to a variable magnetic field detection unit (the magnetic state of the magnetic state variable member is in a second state) included in a magnetic sensor according to Example 2-2. Figure 18B is a diagram illustrating a state after a measurement magnetic field is applied to a variable magnetic field detection unit (the magnetic state of the magnetic state variable member is in a second state) included in a magnetic sensor according to Example 2-2.

[0115] The variable magnetic field detector 100a according to Example 2-2 differs from the variable magnetic field detector 100a according to Example 2-1 in that it does not have a non-magnetic member 41, but the other configurations are the same. Therefore, in the variable magnetic field detector 100a according to Example 2-2, the magnetic state variable member 40 and the free magnetic layer 13 are magnetically coupled. Therefore, as shown in FIG. 17A , in a first state, which is a current-carrying state in which a current 20c flows through the magnetic state modulation member 20 in the X1 direction, a spin orbit torque is generated in the magnetic state variable member 40, and the magnetization 40m of the magnetic state variable member 40 is strongly aligned in the Y2 direction, and also in the free magnetic layer 13 magnetically coupled to the magnetic state variable member 40, the magnetization 13m is strongly aligned in the Y2 direction.

[0116] For this reason, even when the measurement magnetic flux Φ is applied to the magnetic state changeable member 40, the magnetization 40m of the magnetic state changeable member 40 is unlikely to rotate along the X direction, as shown in FIG. 17B. That is, the magnetic state changeable member 40 has a low effective magnetic permeability μ1 in the X direction, which is equivalent to the magnetic permeability μ0 of the surrounding insulator 50. In Example 2-2, the magnetic state changeable member 40 and the free magnetic layer 13 are magnetically coupled, and therefore the free magnetic layer 13 also has a low effective magnetic permeability in the X direction. Therefore, even when the measurement magnetic flux Φ is applied, the free magnetic layer 13 is unlikely to be magnetized in the X1 direction, resulting in a reduced measurement sensitivity of the measurement magnetic field H in the variable magnetic field detection unit 100a.

[0117] On the other hand, in the second state, the application of the current 20c to the magnetic state modulation member 20 is stopped, resulting in a non-energized state. As a result, as shown in FIG. 18A , the magnetic state modulation member 20 no longer controls the orientation of the magnetization 40m of the magnetic state variable member 40. In Example 2-2, the bias magnetic field source 21, such as a permanent magnet, is stacked on the Z2 side of the magnetic state modulation member 20. Therefore, the magnetic field 21m generated by the bias magnetic field source 21 aligns the magnetization 40m of the magnetic state variable member 40 in the Y2 direction, but to a lesser extent than in the first state. Therefore, the effective magnetic permeability in the X direction of the magnetic state variable member 40 and the free magnetic layer 13 magnetically coupled thereto in the second state is higher than the magnetic permeability μ0 of the surrounding insulator 50.

[0118] 18B, the magnetization 40m of the magnetic state changeable member 40 rotates along the measurement magnetic flux Φ and becomes oriented in the X1 direction, which gives the magnetic state changeable member 40 a magnetic collecting function, and the measurement magnetic flux Φ is concentrated in the magnetic state changeable member 40. Here, because the magnetic state changeable member 40 is magnetically coupled to the free magnetic layer 13, the magnetic flux oriented in the X1 direction, which has a higher density than in the first state (FIG. 17B), reaches the free magnetic layer 13 under the influence of the magnetization 40m of the magnetic state changeable member 40.

[0119] In this way, in the second state of Example 2-2, when the measurement magnetic field H is applied, the free magnetic layer 13 is magnetized more strongly in the X1 direction than in the first state, so the measurement sensitivity of the magnetic sensor element 10a to the measurement magnetic field H is relatively higher in the second state. Therefore, by subtracting the first output from the second output in the magnetic field calculation unit 4, it is possible to obtain a measurement signal from which 1 / f noise has been appropriately removed.

[0120] In the examples (Examples 2-1 and 2-2) having the above-described Type B configuration, the bias magnetic field source 21 was a permanent magnet, but is not limited to this. The bias magnetic field may be a magnetic field based on exchange coupling or an induced magnetic field from a current-carrying coil, and a member that provides these magnetic fields can serve as the bias magnetic field source 21. Furthermore, while current is applied to the magnetic state modulation member 20 in the X1 direction in the first state, it may also be in the X2 direction. As a result, the magnetization 40m of the magnetic state variable member 40 is oriented in the Y1 direction, but in this case too, the magnetization 40m is unlikely to rotate even when subjected to a measurement magnetic flux Φ with a large component in the X1 direction.

[0121] Although the bias magnetic field applied to the magnetic state variable member 40 in the second state was oriented in the Y2 direction, this is not limiting. It is sufficient that the magnetic state variable member 40 is magnetized in a direction that makes it easy to magnetize with the measurement magnetic flux Φ, and from this perspective, it may be preferable for the bias magnetic field to be oriented in the in-plane direction of the XY plane. Since the measurement magnetic flux Φ has the largest component oriented in the X1 direction, from the perspective of reducing hysteresis, it may be preferable for the bias magnetic field to be oriented along the X direction, i.e., in the X1 or X2 direction.

[0122] (Example 3-1) Figure 19A is a diagram illustrating a state before a measurement magnetic field is applied to a variable magnetic field detection unit (the magnetic state of the magnetic state variable member is in a first state) included in a magnetic sensor according to an example (Example 3-1) having a configuration in which the variable magnetic field detection unit is Type C and the first embodiment (the magnetic state variable member 40 and the magnetic sensing unit of the magnetic detector element are magnetically uncoupled). Figure 19B is a diagram illustrating a state after a measurement magnetic field is applied to a variable magnetic field detection unit (the magnetic state of the magnetic state variable member is in a first state) included in a magnetic sensor according to Example 3-1. Figure 20A is a diagram illustrating a state before a measurement magnetic field is applied to a variable magnetic field detection unit (the magnetic state of the magnetic state variable member is in a second state) included in a magnetic sensor according to Example 3-1. Figure 20B is a diagram illustrating a state after a measurement magnetic field is applied to a variable magnetic field detection unit (the magnetic state of the magnetic state variable member is in a second state) included in a magnetic sensor according to Example 3-1.

[0123] The variable magnetic field detecting unit 100a according to Example 3-1 has a non-magnetic member 41, and the magnetic state variable member 40 and the free magnetic layer 13 are not magnetically coupled, similar to the variable magnetic field detecting unit 100a according to Example 1-1.

[0124] In the first state, a current 20c is passed through the magnetic state modulation member 20 in the Y direction, specifically in the Y1 direction, to establish a current-carrying state. The application of current causes spin injection from the magnetic state modulation member 20 to the magnetic state variable member 40, which generates a spin orbit torque in the magnetic state variable member 40, as in Example 1-1, and as shown in Figure 19A, the magnetization 40m of the magnetic state variable member 40 is strongly aligned in the Z1 direction.

[0125] When the magnetic state changeable member 40 is aligned in the thickness direction (Z direction) in this way, its magnetization 40m does not change easily. Therefore, even if a measurement magnetic flux Φ is applied to the magnetic state changeable member 40, the magnetization 40m of the magnetic state changeable member 40 is unlikely to rotate along the X direction, as shown in FIG. 19B . That is, the magnetic state changeable member 40 has a low effective magnetic permeability μ1 in the X direction, which is equivalent to the magnetic permeability μ0 of the surrounding insulator 50. Therefore, the magnetic state changeable member 40 is unlikely to affect the measurement magnetic flux Φ that reaches the free magnetic layer 13 of the magnetic detector element 10a, and the measurement of the measurement magnetic flux Φ in the magnetic detector element 10a is performed in a magnetic environment similar to that in the absence of the magnetic state changeable member 40 (i.e., when the magnetic state changeable member 40 is replaced by the insulator 50).

[0126] On the other hand, in the second state, the application of the current 20c to the magnetic state modulation member 20 is stopped, resulting in a non-energized state. As a result, as shown in FIG. 20A , the magnetic state modulation member 20 no longer controls the direction of the magnetization 40m of the magnetic state variable member 40. In Example 3-1, the magnetic state modulation member 20 is made of an antiferromagnetic material. The exchange coupling 20af of this magnetic state modulation member 20 functions as a bias magnetic field source, and the magnetic state variable member 40 is relatively weakly magnetized in the Y2 direction. Therefore, the magnetic state variable member 40 in the second state can be magnetized in the X direction more easily than in the first state, and the effective magnetic permeability μ2 in the X direction of the magnetic state variable member 40 is higher than the magnetic permeability μ0 of the surrounding insulator 50.

[0127] 20B, when the measurement magnetic field H is applied in this state, the magnetization 40m of the magnetic state variable member 40 rotates along the measurement magnetic flux Φ and becomes oriented in the X1 direction, which causes the magnetic state variable member 40 to have a magnetic collecting function, and the measurement magnetic flux Φ is concentrated in the magnetic state variable member 40. As a result, the density of the measurement magnetic flux Φ that reaches the free magnetic layer 13 of the magnetic detector element 10a decreases, and the measurement sensitivity of the measurement magnetic field H in the variable magnetic field detector 100a decreases compared to the first state.

[0128] Thus, in Example 3-1, the measurement magnetic flux Φ is more likely to reach the magnetic detector element 10a in the first state than in the second state, and therefore, by subtracting the second output from the first output in the magnetic field calculation unit 4, a measurement signal in which 1 / f noise has been appropriately removed can be obtained.

[0129] (Example 3-2) Figure 21A is a diagram illustrating a state before a measurement magnetic field is applied to a variable magnetic field detection unit (the magnetic state of the magnetic state variable member is in the first state) included in a magnetic sensor according to an example (Example 3-2) having a configuration in which the variable magnetic field detection unit is Type C and the second embodiment (the magnetic state variable member 40 and the magnetic sensing unit of the magnetic detector element are magnetically coupled). Figure 21B is a diagram illustrating a state after a measurement magnetic field is applied to a variable magnetic field detection unit (the magnetic state of the magnetic state variable member is in the first state) included in a magnetic sensor according to Example 3-2. Figure 22A is a diagram illustrating a state before a measurement magnetic field is applied to a variable magnetic field detection unit (the magnetic state of the magnetic state variable member is in the second state) included in a magnetic sensor according to Example 3-2. Figure 22B is a diagram illustrating a state after a measurement magnetic field is applied to a variable magnetic field detection unit (the magnetic state of the magnetic state variable member is in the second state) included in a magnetic sensor according to Example 3-2.

[0130] The variable magnetic field detector 100a according to Example 3-2 differs from the variable magnetic field detector 100a according to Example 3-1 in that it does not have a non-magnetic member 41, but the other configurations are the same. Therefore, in the variable magnetic field detector 100a according to Example 3-2, the magnetic state variable member 40 and the free magnetic layer 13 are magnetically coupled. Therefore, as shown in FIG. 21A , in the first state, which is a current-carrying state in which a current 20c in the X1 direction flows through the magnetic state modulation member 20, a spin orbit torque is generated in the magnetic state variable member 40, causing the magnetization 40m of the magnetic state variable member 40 to align in the Z1 direction, and also in the free magnetic layer 13 magnetically coupled to the magnetic state variable member 40, the magnetization 13m is strongly aligned in the Z1 direction.

[0131] For this reason, even when the measurement magnetic flux Φ is applied to the magnetic state changeable member 40, the magnetization 40m of the magnetic state changeable member 40 is unlikely to rotate along the X direction, as shown in FIG. 21B . That is, the magnetic state changeable member 40 has a low effective magnetic permeability μ1 in the X direction, which is equivalent to the permeability μ0 of the surrounding insulator 50. In Example 3-2, the magnetic state changeable member 40 and the free magnetic layer 13 are magnetically coupled, and therefore the free magnetic layer 13 also has a low effective magnetic permeability in the X direction. Therefore, even when the measurement magnetic flux Φ is applied, the free magnetic layer 13 is unlikely to be magnetized in the X1 direction, resulting in a reduced measurement sensitivity of the measurement magnetic field H in the variable magnetic field detection unit 100a.

[0132] On the other hand, in the second state, the application of the current 20c to the magnetic state modulation member 20 is stopped to set the magnetic state modulation member 20 in a non-energized state. As a result, as shown in FIG. 22A , the magnetic state modulation member 20 no longer controls the direction of the magnetization 40m of the magnetic state variable member 40. In Example 3-2, the magnetic state modulation member 20 has a portion made of an antiferromagnetic material, and due to the exchange coupling 20af between this antiferromagnetic material and the magnetic state variable member 40, the magnetization 40m of the magnetic state variable member 40 is oriented in the Y2 direction, but the degree of magnetization is relatively weak. Based on the magnetization of the magnetic state variable member 40, the magnetization 13m of the free magnetic layer 13 magnetically coupled to the magnetic state variable member 40 is also oriented in the Y2 direction, and the degree of magnetization is relatively weak, similar to the magnetization 40m of the magnetic state variable member 40. Therefore, the magnetic state variable member 40 and the free magnetic layer 13 in the second state can be magnetized in the X direction more easily than in the first state. That is, the effective magnetic permeability μ2 of the magnetic state variable member 40 in the X direction is higher than the magnetic permeability μ0 of the surrounding insulator 50.

[0133] 22B, when a measurement magnetic field H is applied, the magnetization 40m of the magnetic state changeable member 40 rotates along the measurement magnetic flux Φ and becomes oriented in the X1 direction, which gives the magnetic state changeable member 40 a magnetic collecting function and causes the measurement magnetic flux Φ to concentrate in the magnetic state changeable member 40. Here, the free magnetic layer 13 is magnetically coupled to the magnetic state changeable member 40, and therefore, under the influence of the magnetization 40m of the magnetic state changeable member 40, magnetic flux oriented in the X1 direction, which has a density higher than that in the first state (FIG. 21B), reaches the free magnetic layer 13.

[0134] In this way, in the second state of Example 3-2, when the measurement magnetic field H is applied, the free magnetic layer 13 is magnetized more strongly in the X1 direction than in the first state, so the measurement sensitivity of the measurement magnetic field H of the magnetic detector element 10a is relatively higher in the second state. Therefore, by subtracting the first output from the second output in the magnetic field calculation unit 4, it is possible to obtain a measurement signal from which 1 / f noise has been appropriately removed.

[0135] In the examples (Examples 3-1 and 3-2) having the above-described Type C configuration, the exchange coupling 20af serves as the bias magnetic field source to apply the bias magnetic field, but this is not limiting. The bias magnetic field may be a magnetic field from a permanent magnet or an induced magnetic field from a current-carrying coil, and a member that applies these magnetic fields may serve as the bias magnetic field source 21. Furthermore, while current is applied to the magnetic state modulation member 20 in the Y2 direction in the first state, it may also be in the Y1 direction. As a result, the magnetization 40m of the magnetic state variable member 40 is oriented in the Z2 direction, but even in this case, the magnetization 40m is unlikely to rotate even when subjected to a measurement magnetic flux Φ with a large component in the X1 direction.

[0136] Although the bias magnetic field applied to the magnetic state changeable member 40 in the second state was oriented in the Y2 direction, this is not limiting. It is sufficient that the magnetization 40m of the magnetic state changeable member 40, which has been set in a predetermined direction by the bias magnetic field, is oriented in a direction that makes it easy for it to rotate along the direction of the measurement magnetic flux Φ when the magnetic state changeable member 40 is subjected to the measurement magnetic flux Φ. From this perspective, it may be preferable that the bias magnetic field be oriented in the in-plane direction of the XY plane. Since the measurement magnetic flux Φ has the largest component oriented in the X1 direction, from the perspective of reducing hysteresis, it may be preferable that the bias magnetic field be oriented along the X direction, i.e., in the X1 or X2 direction.

[0137] The above-described embodiments have been described to facilitate understanding of the present invention, and are not intended to limit the present invention. Therefore, each element disclosed in the above embodiments is intended to include all design modifications and equivalents that fall within the technical scope of the present invention.

[0138] In the above description, the stacking direction of the magnetic state variable member 40 and the magnetic state modulation member 20 in the magnetic control body 60 and the arrangement direction of the magnetic detection element 10a and the magnetic control body 60 were both in the second direction, but this is not limited thereto. For example, the magnetic state variable member 40 and the magnetic state modulation member 20 may be stacked in the first direction or the third direction. Furthermore, while the boundary between the magnetic state variable member 40 and the magnetic state modulation member 20 in the magnetic control body 60 was a plane parallel to the XY plane, this is not limited thereto. The surface formed by the boundary may have a portion inclined with respect to the XY plane. Specific examples of such cases include a configuration in which the boundary is flat but inclined with respect to the XY plane, a configuration in which the boundary is curved, a configuration in which the boundary has a bent portion, and a configuration in which the boundary forms a pattern when viewed from the stacking direction. Furthermore, the wiring for applying current to the magnetic state modulation member 20 may share part of the wiring for measuring the electrical characteristics of the magnetic detection element, thereby simplifying the overall circuit.

[0139] Furthermore, in the above description, the magnetization 40m of the magnetic state variable member 40 rotates due to the spin orbit torque from the magnetic state modulation member 20, but this is not limited to this, and the magnetization 40m of the magnetic state variable member 40 may also rotate due to the spin transfer torque, or both the spin orbit torque and the spin transfer torque may contribute to the rotation of the magnetization 40m of the magnetic state variable member 40.

[0140] In particular, when the magnetic control body 60 has an electromagnetically conductive state variable member 601 that combines the functions of the magnetic state variable member 40 and the magnetic state modulation member 20, as shown in Fig. 23, by passing a current 601c through the electromagnetically conductive state variable member 601, both the spin orbit torque and the spin transfer torque may contribute, causing the magnetization 601m of the electromagnetically conductive state variable member 601 to rotate. Note that Fig. 23 is a modified example of the variable magnetic field detector example 2-1 shown in Fig. 15B, and is a diagram illustrating a state in which a measurement magnetic field is applied to the variable magnetic field detector (the magnetic state of the magnetic state variable member is in the first state) provided in the magnetic sensor according to the modified example.

[0141] The present invention is useful as a magnetic sensor and a magnetic measurement method having high magnetic resolution, which can detect an external magnetic field with high sensitivity.

[0142] 1: Magnetic sensor 2: Magnetic field detection unit 3: Control power supply 4: Magnetic field calculation unit 5: Amplifier 6: A / D conversion circuit 7: Control unit 10P: Detection center 10a, 10b, 10c, 10d: Magnetic detection element 11: Fixed magnetic layer 11m, 13m, 40m, 601m: Magnetization 12: Intermediate layer 13: Free magnetic layer 15: Full bridge circuit 20: Magnetic state modulation member 20af: Exchange coupling 20c, 601c: Current 21: Bias magnetic field source 21m: Magnetic field 31: First magnetic body 32: Second magnetic body 40: Magnetic state variable member 41: Non-magnetic member 50: Insulator 60: Magnetic control body 601: Electromagnetic state variable member 100a, 100b, 100c, 100d: Variable magnetic field detection unit 311: First end GND: Ground terminal H: Measured magnetic field V1, V2: Output terminals Vdd: Power supply terminal Φ: Measured magnetic flux

Claims

1. A magnetic sensor characterized by comprising a variable magnetic field detection unit having: a first magnetic body that is magnetized by a measurement magnetic field in a first direction; a magnetic detection element that is located on one side of a first end of the first magnetic body in the first direction and has a sensitivity axis along the first direction; a magnetic state variable member that is located on one side of the first end of the first magnetic body in the first direction and can take a first state and a second state in which the magnetic state differs, including at least one of effective permeability and magnetization direction; and a magnetic state modulation member that changes the magnetic state of the magnetic state variable member.

2. A magnetic sensor as described in claim 1, further comprising a magnetic field calculation unit that calculates the measured magnetic field based on a first output from the variable magnetic field detection unit when the magnetic state variable member is in the first state and a second output from the variable magnetic field detection unit when the magnetic state variable member is in the second state.

3. A magnetic sensor as described in claim 2, wherein the effective permeability μ2 in the first direction of the magnetic state changeable member in the second state is higher than the effective permeability μ1 in the first direction of the magnetic state changeable member in the first state, and higher than the permeability μ0 in the first direction of a first material located between the first magnetic body and the magnetic detection element.

4. A magnetic sensor as described in claim 3, wherein the variable magnetic field detection unit has a non-magnetic member between the magnetic detection element and the magnetic state changeable member, and the magnetic sensing portion of the magnetic detection element is magnetically uncoupled from the magnetic state changeable member.

5. The magnetic sensor according to claim 3, wherein the magnetic sensing portion of the magnetic detector element is magnetically coupled to the magnetic state variable member.

6. The magnetic sensor according to claim 3, wherein the magnetic detector element and the magnetic state changeable member are aligned in a second direction perpendicular to the first direction.

7. The magnetic sensor according to claim 6, wherein the magnetic state changeable member has a portion closer to the first magnetic body in the first direction than the detection center of the magnetic detection element.

8. The magnetic sensor according to claim 6, wherein the center of the magnetic state changeable member in the first direction and the detection center of the magnetic detection element are at the same position in the first direction.

9. The magnetic sensor according to claim 8, wherein the length of the magnetic state changeable member in the first direction is longer than the length of the magnetic detector element in the first direction.

10. The magnetic sensor according to claim 6, wherein the length of the first magnetic body in the first direction is longer than the length of the first magnetic body in the second direction.

11. The magnetic sensor according to claim 1, wherein the variable magnetic field detection unit further comprises a second magnetic body that is more distal in the first direction than the magnetic detection element when viewed from the first end.

12. The magnetic sensor according to claim 11, wherein the magnetic state variable member is arranged so as to be magnetically coupled to the first magnetic body and the second magnetic body in the second state.

13. A magnetic sensor as described in claim 3 or claim 4, wherein the magnetic state modulation member and the magnetic state changeable member form a magnetic control body stacked in a second direction perpendicular to the first direction, the magnetic control body and the magnetic detection element are arranged side by side in the second direction, the magnetic state modulation member has a spin torque generation unit that imparts a spin orbit torque to the magnetic state changeable member when current is applied, and the magnetic state of the magnetic state changeable member when current is applied differs from the magnetic state when current is not applied based on the spin orbit torque from the spin torque generation unit.

14. The magnetic sensor described in claim 13, wherein the variable magnetic field detection unit has a bias magnetic field source that magnetizes the magnetic state variable member along the second direction to an extent that the magnetization does not rotate due to the measurement magnetic field when the magnetic state modulation member is in a non-conductive state, the magnetic state variable member is in the first state when the magnetic state modulation member is in a non-conductive state, and the magnetic state variable member is in the second state when the magnetic state modulation member is in a conductive state and a current flows in an in-plane direction of a first surface having a normal along the second direction, and in the second state, the magnetic state variable member is magnetized in a direction opposite to the direction of current flow to an extent that the magnetization can rotate in the in-plane direction of the first surface due to a magnetic field based on the measurement magnetic field when subjected to the spin orbit torque.

15. The magnetic sensor of claim 14, wherein in the second state, the current flowing through the magnetic state modulation member is along a third direction in-plane of the first surface and perpendicular to the first direction.

16. The magnetic sensor according to claim 14, wherein the magnetic state modulating member has an antiferromagnetic portion made of antiferromagnetic material, and the exchange coupling between the antiferromagnetic portion and the magnetic state variable member serves as the bias magnetic field source.

17. The magnetic sensor according to claim 14, wherein the bias magnetic field source includes at least one of a coil that generates an induced magnetic field when energized, and a permanent magnet.

18. The magnetic sensor according to claim 17, wherein the bias magnetic field source is laminated on the magnetic control body.

19. A magnetic sensor as described in claim 13, wherein when the magnetic state modulation member is in a conducting state and a current flows along the first direction, the magnetic state changeable member is in the first state, and in the first state, the magnetic state changeable member is subjected to the spin orbit torque and is magnetized in a third direction perpendicular to the first and second directions by magnetic flux based on the measured magnetic field, and the magnetization of the magnetic state changeable member is less likely to rotate by magnetic flux based on the measured magnetic field than in the second state; and when the magnetic state modulation member is in a non-conducting state, the magnetic state changeable member is in the second state, and in the second state, the magnetization of the magnetic state changeable member is more likely to orient in the first direction by magnetic flux based on the measured magnetic field than in the first state.

20. A magnetic sensor as described in claim 19, wherein the variable magnetic field detection unit has a bias magnetic field source that applies a bias magnetic field to the magnetic state variable member, and the bias magnetic field that the magnetic state variable member receives in the second state is along the in-plane direction of a first surface having a normal along the second direction, and is to an extent that the magnetization of the magnetic state variable member can be rotated by magnetic flux based on the measurement magnetic field.

21. The magnetic sensor of claim 20, wherein the bias magnetic field is along a third direction that is orthogonal to the first direction and the second direction.

22. A magnetic sensor as described in claim 13, wherein when the magnetic state modulation member is in a conducting state and a current flows along the first direction, the magnetic state variable member is in the first state, and in the first state, the magnetic state variable member is subjected to the spin orbit torque and is magnetized in the first and second directions by magnetic flux based on the measured magnetic field, and the magnetization of the magnetic state variable member is less likely to rotate by magnetic flux based on the measured magnetic field than in the second state; and when the magnetic state modulation member is in a non-conducting state, the magnetic state variable member is in the second state, and in the second state, the magnetization of the magnetic state variable member is more likely to orient in the first direction by magnetic flux based on the measured magnetic field than in the first state.

23. A magnetic sensor as described in claim 22, wherein the variable magnetic field detection unit has a bias magnetic field source that applies a bias magnetic field to the magnetic state variable member, and the bias magnetic field that the magnetic state variable member receives in the second state is along the in-plane direction of a first surface having a normal along the second direction, and is to an extent that the magnetization of the magnetic state variable member can be rotated by magnetic flux based on the measurement magnetic field.

24. The magnetic sensor of claim 23, wherein the bias magnetic field is along a third direction orthogonal to the first direction and the second direction.

25. A magnetic measurement method using a magnetic sensor comprising: a variable magnetic field detection unit having: a first magnetic body that is magnetized by a measurement magnetic field in a first direction; a magnetic detection element that is located on one side in the first direction of a first end of the first magnetic body, which is one end of the first magnetic body in the first direction, and has a sensitivity axis along the first direction; a magnetic state changeable member that is located on the one side in the first direction of the first end of the first magnetic body, and that can take a first state and a second state in which the magnetic state including at least one of effective permeability and magnetization direction differs; and a magnetic state modulation member that changes the magnetic state of the magnetic state changeable member; and a magnetic field calculation unit that calculates the measurement magnetic field from a first output from the variable magnetic field detection unit when the magnetic state changeable member is in the first state and a second output from the variable magnetic field detection unit when the magnetic state changeable member is in the second state, the method comprising: a first measurement step of setting the magnetic state changeable member to the first state and obtaining the first output when the measurement magnetic field is applied; A magnetic measurement method comprising: a second measurement step of setting the magnetic state variable member to the second state and obtaining the second output while the measurement magnetic field is applied; and a magnetic field calculation step of calculating the measurement magnetic field from the first output and the second output in the magnetic field calculation unit.

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