Magnetic sensor and magnetic measurement method

Abstract

A magnetic sensor 1 according to the present invention, which is capable of measuring a small magnetic field with high accuracy, comprises a variable magnetic field detection unit 100a having: a magnetoresistive element 10a that has a first layer 13 which can be magnetized in the direction along a measurement magnetic field, a second layer 11 which is capable of maintaining the magnetization direction in a first direction (X direction), and a non-magnetic layer 12 which is located between the first layer 13 and the second layer 11; and a magnetization control unit 20 that reversibly inverts the direction of the magnetization 11m of the second layer 11. The magnetization control unit 20 may be an energization magnetization control unit 201 in which the magnetization direction is inverted by energization, or may have a spin Hall layer 21 and an anisotropy variable layer 22. The magnetization control unit 20 may have the spin Hall layer 21 and the second layer 11 may be a variable second layer 111, or the second layer 11 may be integrated with the magnetization control unit 20 so as to be an energization variable second layer 112.

Description

Magnetic Sensor and Magnetic Measurement Method

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

[0002] As a magnetic sensor for detecting and measuring a magnetic field, there is one provided with a magnetoresistive element using a GMR (giant magnetoresistance) effect or a TMR (tunnel magnetoresistance) effect. The magnetoresistive element in these magnetic sensors has a configuration in which a fixed magnetic layer, a non-magnetic intermediate layer, and a free magnetic layer are laminated 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, and a resistance change corresponding to the angle formed by the magnetization direction of the free magnetic layer and the magnetization direction of the fixed magnetic layer occurs. A magnetic sensor provided with a magnetoresistive element can detect a magnetic field using the resistance change of the magnetoresistive element.

[0003] A magnetic sensor provided with a magnetoresistive element has 1 / f noise that cannot be removed by a filter. Since 1 / f noise is inversely proportional to the frequency and becomes larger as the frequency becomes lower, it may be an inhibiting factor when performing high-precision measurement. For this reason, various methods are used to remove 1 / f noise.

[0004] Patent Document 1 discloses a 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) in an even-function type magnetic sensor.

[0005] Patent Document 2 discloses a measuring device that removes noise due to a Schottky barrier generated between an electrode and a sample when measuring the Hall electromotive force of a semiconductor sample, by shifting the frequency band of a voltage difference Vm to the low-frequency side and removing the frequency band of the voltage difference Vm that is greatly affected by 1 / f noise.

[0006] Patent Document 3 discloses a magnetic field sensing device that samples a bridge signal with each of a first current and a second current by switching two sample holds, and determines the value of a 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 polarity of the sensor signal and takes the difference between the modulated signals in order to remove 1 / f noise from the output signal.

[0008] Japanese Patent Publication No. 2018-115972, Japanese Patent Publication No. 2020-148727, Japanese Patent Publication No. 2012-518788, Japanese Patent Publication No. 2009-544004

[0009] There is a strong demand to improve the resolution (magnetic resolution) of magnetic sensors equipped with magnetoresistive elements, and various devices and methods have been proposed to meet this demand. The present invention aims to provide a magnetic sensor equipped with a magnetoresistive element and a magnetic measurement method that can measure small magnetic fields with high precision using a configuration different from conventional methods.

[0010] In one embodiment, the present invention is a magnetic sensor characterized by comprising a magnetoresistive element having a first layer that can be magnetized in a direction along a measurement magnetic field, a second layer that can maintain magnetization in a predetermined direction even when subjected to the measurement magnetic field, and a non-magnetic layer located between the first layer and the second layer, and a variable magnetic field detection unit having a magnetization control unit that changes the direction of magnetization of the second layer.

[0011] In conventional magnetoresistive elements, when measuring an external magnetic field, one of the two magnetic layers becomes a magnetization-fixed layer, fixing the direction of magnetization. However, in a magnetic sensor according to one aspect of the present invention, the external magnetic field is measured in two states: a state in which the magnetization of the second layer corresponding to the magnetization-fixed layer is fixed in one direction (first state), and a state in which the magnetization of the second layer is fixed in a direction different from that of the first state (second state). By taking the difference between the electrical signals including the measurement results in each state, highly accurate measurement becomes possible.

[0012] In the magnetic sensor described above, the magnetization control unit may form a laminated structure with the magnetoresistive element.

[0013] In the magnetic sensor described above, the second layer is reversibly switchable between a first state in which the magnetization is maintained in a first direction even when subjected to the measurement magnetic field, and a second state in which the magnetization is maintained in a second direction different from the first direction even when subjected to the measurement magnetic field, and when the second layer is in the second state, the magnetization control unit may be energized. In this case, when the second layer is in the first state, the magnetization control unit may be de-energized, and when the second layer is in the first state, the magnetization control unit may be energized in a different state than when the second layer is in the first state.

[0014] In the magnetic sensor described above, the magnetization control unit has a spin Hall layer made of a layered body that generates a spin-orbit torque when energized, and the direction of the magnetization of the second layer may be reversibly changed based on the spin-orbit torque from the spin Hall layer. In this case, the spin Hall layer may have a portion made of a non-magnetic material and / or a portion made of an antiferromagnetic material.

[0015] In the magnetic sensor described above, the magnetization control unit forms a laminated structure with the magnetoresistive element, and the magnetization control unit is made of a layered body located between the spin Hall layer and the second layer, and has an anisotropic variable layer that is magnetically coupled to the second layer and has magnetic anisotropy, and the anisotropic variable layer may have its magnetization direction reversibly changed by receiving the spin orbit torque from the spin Hall layer. In this case, the anisotropic variable layer may have a portion made of a ferromagnetic material and / or a portion made of an antiferromagnetic material.

[0016] In the magnetic sensor described above, the magnetization control unit may be provided with a bias magnetic field source that aligns the magnetization of at least a portion of the anisotropic variable layer to a predetermined direction when the magnetization control unit is in an unenergized state. The bias magnetic field source may be based on exchange coupling between an antiferromagnetic material and a magnetic material. The spin Hall layer may have a portion made of an antiferromagnetic material that constitutes the bias magnetic field source. The spin Hall layer may have a portion made of a non-magnetic material. The anisotropic variable layer may have a portion made of an antiferromagnetic material that constitutes the bias magnetic field source. The anisotropic variable layer may have at least one of shape magnetic anisotropy and crystal magnetic anisotropy as the bias magnetic field source.

[0017] In the magnetic sensor described above, the magnetization control unit is an electromagnetically driven magnetization control unit capable of reversibly changing the direction of magnetization by energizing, and the electromagnetically driven magnetization control unit may be magnetically coupled to the second layer. In this case, the electromagnetically driven magnetization control unit may have a portion made of an antiferromagnetic material and / or a portion that produces a spin Hall effect.

[0018] In the magnetic sensor having the spin Hall layer described above, the second layer may be a variable second layer whose magnetization direction is changed by receiving the spin-orbit torque from the spin Hall layer. In this case, the variable second layer may have a portion made of a ferromagnetic material and / or a portion made of an antiferromagnetic material.

[0019] Another aspect of the present invention is a magnetic sensor having a variable magnetic field detection unit having a magnetoresistive element comprising: a first layer that can be magnetized in a direction along a measuring magnetic field; a second layer that can maintain a state in which the magnetization is along a first direction even when subjected to the measuring magnetic field; and a non-magnetic layer located between the first layer and the second layer, wherein the second layer is reversibly switchable between a first state in which the magnetization is maintained in a first direction even when subjected to the measuring magnetic field, and a second state in which the magnetization is maintained in a second direction different from the first direction even when subjected to the measuring magnetic field.

[0020] In the magnetic sensor described above, the second layer may be a variable-energy second layer that enters the second state when the second layer is energized. In this case, the variable-energy second layer may have a portion made of an antiferromagnetic material and / or a portion that produces a spin Hall effect.

[0021] In the magnetic sensor described above, when the variable-energy second layer is in the first state, the variable-energy second layer may be in a non-energized state, or it may be in an energized state different from when the variable-energy second layer is in the first state.

[0022] In the magnetic sensor described above, the first orientation and the second orientation may be in the same direction but opposite. In this case, the magnetic field calculation unit may be provided to calculate the measured magnetic field based on a first output from the variable magnetic field detection unit when the magnetization of the second layer is in the first orientation and a second output from the variable magnetic field detection unit when the magnetization of the second layer is in the second orientation.

[0023] If there is a correlation between the noise contained in the electrical signal based on the first output and the electrical signal based on the second output, the noise signal, especially 1 / f noise, can be removed by taking the difference between these electrical signals.

[0024] The magnetic sensor described above may include a magnetic field detection unit having a half-bridge circuit that includes two of the variable magnetic field detection units, wherein the magnetic field detection unit is capable of outputting a first signal output from the half-bridge circuit when the second layer of one of the two variable magnetic field detection units is in the first state, and a second signal output from the half-bridge circuit when the second layer of one of the two variable magnetic field detection units is in the second state, and may also include a magnetic field calculation unit that calculates the measured magnetic field based on the first signal and the second signal.

[0025] The magnetic sensor described above may include a magnetic field detection unit having a full bridge circuit including four variable magnetic field detection units, wherein the magnetic field detection unit is capable of outputting a first signal output from the full bridge circuit when the second layer of two of the four variable magnetic field detection units is in the first state, and a second signal output from the full bridge circuit when the magnetization of the second layer of the four variable magnetic field detection units is in the opposite direction to when the first signal is output, and may also include a magnetic field calculation unit that calculates the measured magnetic field based on the first signal and the second signal.

[0026] If there is a correlation between the noise contained in the first signal and the second signal, the noise signal, especially 1 / f noise, can be removed by taking the difference between these signals.

[0027] In the magnetic sensor described above, each variable magnetic field detection unit is reversibly switchable between a first state and a second state, and comprises a first variable magnetic field detection unit and a second variable magnetic field detection unit connected in series, and an output unit that outputs an electrical signal relating to the potential between the first variable magnetic field detection unit and the second variable magnetic field detection unit connected in series, wherein the second layers of the first and second variable magnetic field detection units are controlled to magnetize in opposite directions to each other, and further comprises a magnetic field calculation unit that performs calculation processing using the electrical signal from the output unit as input to calculate the measured magnetic field, wherein the calculation processing may include determining the difference between a first electrical signal output from the output unit when the magnetization of the second layer of the first variable magnetic field detection unit is in the first direction, and a second electrical signal output from the output unit when the magnetization of the second layer of the first variable magnetic field detection unit is in the second direction.

[0028] In the magnetic sensor described above, the first orientation and the second orientation may be aligned in different directions. In this case, the first orientation may be aligned in a first orthogonal direction which is one of the directions perpendicular to the stacking direction in which the first layer and the second layer are aligned, and the second orientation may be aligned in a second orthogonal direction which is perpendicular to the stacking direction and intersects the first orthogonal direction, and furthermore, the first orthogonal direction and the second orthogonal direction may be perpendicular to each other.

[0029] In the above case, the first orientation may be along a first orthogonal direction which is one of the directions perpendicular to the stacking direction in which the first layer and the second layer are aligned, and the second orientation may be along the stacking direction, or the first orientation may be along the stacking direction which is one of the directions perpendicular to the stacking direction, and the measurement magnetic field may have a component along the first orientation and a component along the second orientation.

[0030] In the above case, the system may further include a magnetic field calculation unit that calculates the strength of the measured magnetic field based on a first output from the variable magnetic field detection unit when the second layer is in the first state and a second output from the variable magnetic field detection unit when the second layer is in the second state. Alternatively, the system may further include a magnetic field calculation unit that calculates the direction of the measured magnetic field based on a first output from the variable magnetic field detection unit when the second layer is in the first state and a second output from the variable magnetic field detection unit when the second layer is in the second state.

[0031] The magnetic sensor described above may include a second layer bias magnetic field source that, in the first state, applies a magnetic field to the second layer to maintain the magnetization of the second layer in the first direction. In this case, the magnetization control unit has an antiferromagnetic section made of an antiferromagnetic material, and the exchange coupling based on the antiferromagnetic section may become the second layer bias magnetic field source.

[0032] The above-described magnetic sensor may include a second layer bias magnetic field source that, in the first state, applies a magnetic field to the second layer to maintain the magnetization of the second layer in the first direction. In this case, the variable current second layer has a junction between an antiferromagnetic material and a ferromagnetic material, and the exchange coupling that occurs at the junction may become the second layer bias magnetic field source.

[0033] In the magnetic sensor described above, the second layer bias magnetic field source may include at least one of a coil that generates an induced magnetic field when energized and a permanent magnet, the second layer bias magnetic field source and the second layer may be aligned in the stacking direction in which the first layer and the second layer are aligned, or the second layer bias magnetic field source and the second layer may be aligned in a direction that intersects the stacking direction in which the first layer and the second layer are aligned.

[0034] When the magnetic sensor described above is in the first state, the magnetization of the second layer may be maintained in the first orientation based on shape magnetic anisotropy and / or crystal magnetic anisotropy.

[0035] In another aspect, the present invention provides a magnetic measurement method using a magnetic sensor, comprising: a magnetoresistive element having a first layer that can be magnetized in a direction along a measurement magnetic field; a second layer that can maintain magnetization in a predetermined direction even when subjected to the measurement magnetic field; and a non-magnetic layer located between the first and second layers; a variable magnetic field detection unit having a magnetization control unit that changes the direction of the magnetization of the second layer; a magnetic field calculation unit that calculates the measurement magnetic field based on a first output from the variable magnetic field detection unit in a first state in which the magnetization of the second layer is maintained in a first direction even when subjected to the measurement magnetic field; and a second output from the variable magnetic field detection unit in a second state in which the magnetization of the second layer is maintained in a second direction different from the first direction even when subjected to the measurement magnetic field, wherein the second layer can be reversibly switched between the first and second states. The magnetic measurement method comprises a first step of causing the variable magnetic field detection unit to output the first output, a second step of causing the variable magnetic field detection unit to output the second output, and a third step of the magnetic field calculation unit calculating the measurement magnetic field based on the first output and the second output.

[0036] In yet another aspect, the present invention provides a magnetic measurement method using a magnetic sensor, comprising: a variable magnetic field detection unit having a magnetoresistive element having a first layer that can be magnetized in a direction along a measurement magnetic field, a second layer that can maintain magnetization in a predetermined direction even when subjected to the measurement magnetic field, and a non-magnetic layer located between the first and second layers; a magnetic field calculation unit that calculates the measurement magnetic field based on a first output from the variable magnetic field detection unit in a first state in which the magnetization of the second layer is maintained in a first direction even when subjected to the measurement magnetic field, and a second output from the variable magnetic field detection unit in a second state in which the magnetization of the second layer is maintained in a second direction different from the first direction even when subjected to the measurement magnetic field, wherein the second layer is reversibly switchable between the first and second states, and is an energetically variable second layer that enters the second state when the second layer is energized. The magnetic measurement method comprises a first step of causing the variable magnetic field detection unit to output the first output, a second step of causing the variable magnetic field detection unit to output the second output, and a third step of the magnetic field calculation unit calculating the measurement magnetic field based on the first output and the second output.

[0037] In the magnetic sensor of the magnetic measurement method described above, the first orientation and the second orientation may be opposite but in the same direction, and the direction of the measured magnetic field may be calculated based on the first output and the second output. Alternatively, the first orientation and the second orientation may be along different directions, and the direction of the measured magnetic field may be calculated based on the first output and the second output.

[0038] The magnetic sensor of the above-described magnetic measurement method comprises a magnetic field detection unit having a half-bridge circuit including two variable magnetic field detection units, wherein the magnetic field detection unit may output a first signal when one of the two variable magnetic field detection units of the half-bridge circuit is in the first state, and output a second signal when it is in the second state. In this case, the above-described magnetic measurement method may, instead of the first to third steps, comprise an I step of causing the magnetic field detection unit to output the first signal, a II step of causing the magnetic field detection unit to output the second signal, and a III step of the magnetic field calculation unit calculating the measured magnetic field based on the first signal and the second signal.

[0039] The magnetic sensor of the above-described magnetic measurement method comprises a magnetic field detection unit having a full-bridge circuit including four variable magnetic field detection units, wherein the magnetic field detection unit outputs a first signal when the magnetization of the second layer of two of the four variable magnetic field detection units of the full-bridge circuit is in the first state and the magnetization of the second layer of the other two is in the second state, and outputs a second signal when the magnetization of the second layer of the four variable magnetic field detection units of the full-bridge circuit is in the opposite direction to when the first signal is output. In this case, the above-described magnetic measurement method may, instead of the first to third steps, comprise an I step of causing the magnetic field detection unit to output a first signal, a II step of causing the magnetic field detection unit to output a second signal, and a III step of the magnetic field calculation unit calculating the measured magnetic field based on the first signal and the second signal.

[0040] In the magnetic sensor described above, in which the first orientation and the second orientation are opposite but in the same direction, the variable magnetic field detection unit is reversibly switchable between the first state and the second state, and comprises a first variable magnetic field detection unit and a second variable magnetic field detection unit connected in series, and an output unit that outputs an electrical signal relating to the potential between the first variable magnetic field detection unit and the second variable magnetic field detection unit connected in series, wherein the second layers of the first and second variable magnetic field detection units are controlled to magnetize in opposite directions to each other, and the magnetic field calculation unit may perform calculation processing using the electrical signal from the output unit as input instead of the first and second outputs. In this case, the above-described magnetic measurement method may, in the first step, cause the variable magnetic field detection unit to output a first electrical signal from the output unit when the magnetization of the second layer of the first variable magnetic field detection unit is in the first direction, instead of the first output; in the second step, cause the variable magnetic field detection unit to output a second electrical signal from the output unit when the magnetization of the second layer of the first variable magnetic field detection unit is in the second direction, instead of the second output; and in the third step, calculate the measured magnetic field based on the first electrical signal and the second electrical signal instead of the first output and the second output.

[0041] In this case, the third step may include calculating the difference between the first electrical signal and the second electrical signal to determine the measured magnetic field.

[0042] According to the present invention, a magnetic sensor and a magnetic measurement method with high magnetic resolution are provided, and the present invention also contributes to further miniaturization of magnetic sensors.

[0043] 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 an example of a variable magnetic field detection unit included in the magnetic sensor according to the first embodiment of the present invention. A diagram for explaining a first state of an example of the variable magnetic field detection unit of the magnetic sensor according to the first embodiment of the present invention. A diagram for explaining a second state of an example of the variable magnetic field detection unit of the magnetic sensor according to the first embodiment of the present invention. A flowchart for explaining a first measurement method using the magnetic sensor according to the first 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 another 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 first state of another example of the variable magnetic field detection unit of the magnetic sensor according to the first embodiment of the present invention. A diagram for explaining a second state of another example of the variable magnetic field detection unit of the magnetic sensor according to the first embodiment of the present invention. A diagram for explaining a modification 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 an example of the variable magnetic field detection unit included in the magnetic sensor according to the second embodiment of the present invention. A diagram for explaining an example of the variable magnetic field detection unit included in the magnetic sensor according to the third embodiment of the present invention. A diagram for explaining a second measurement method (first state) using the magnetic sensor according to the first embodiment of the present invention. A diagram for explaining a second measurement method (second state) using the magnetic sensor according to the first embodiment of the present invention. A diagram for explaining in detail an example of the variable magnetic field detection unit included in the magnetic sensor according to the first embodiment of the present invention. A flowchart for explaining a third measurement method using the magnetic sensor according to the first embodiment of the present invention. A diagram for explaining in detail an example (modification example) of the variable magnetic field detection unit included in the magnetic sensor according to the first embodiment of the present invention. A diagram showing one specific example of a second layer bias magnetic field source. A diagram showing another specific example of a second layer bias magnetic field source. A cross-sectional view taken along line B - B' of FIG. 20. A diagram showing another specific example of a second layer bias magnetic field source. A diagram showing yet another specific example of a second layer bias magnetic field source. A diagram showing still another specific example of a second layer bias magnetic field source.

[0044] Embodiments of the present invention will be described below with reference to the accompanying drawings. In each drawing, the same component is given the same number, and its description is omitted. Reference coordinates are shown in each drawing as appropriate to indicate the positional relationship of each component.

[0045] Figure 1 is a block diagram of a magnetic sensor according to one embodiment of the present invention. Figure 2 is an explanatory diagram of the magnetic field detection unit included 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 and an amplifier 5, an analog-to-digital conversion circuit (A / D conversion circuit 6), and a control unit 7. The control unit 7 controls each part that constitutes the magnetic sensor 1 and is configured as a CPU (central processing unit) and a program, etc.

[0046] The magnetic field detection unit 2 detects the external magnetic field (measured magnetic field H) to be measured. As shown in Figure 2, the magnetic field detection unit 2 is composed of a full-bridge circuit 15 having magnetoresistive elements 10a, 10b, 10c, and 10d that measure the 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 magnetoresistive elements 10a, 10b, 10c, and 10d, respectively. The control power supply 3 applies a predetermined current or voltage to each part based on a control signal from the control unit 7.

[0047] The magnetic field calculation unit 4 calculates the measured magnetic field H based on the output of the magnetic field detection unit 2, and is composed of, for example, a CDS (Correlated Double Sampling) circuit. In one specific example, the magnetic field calculation unit 4 calculates the measured magnetic field H based on a first signal, which is the output signal of the magnetic field detection unit 2 when the two variable magnetic field detection units 100b and 100c are in the first state and the two variable magnetic field detection units 100a and 100d are in the second state, and a second signal, which is the output signal of the magnetic field detection unit 2 when the two variable magnetic field detection units 100a and 100d are in the first state and the two variable magnetic field detection units 100b and 100c are in the second state. For example, by calculating the difference between the signal based on the first signal and the signal based on the second signal, a measurement signal from which 1 / f noise has been removed can be obtained. Details of the first and second states will be described later.

[0048] 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.

[0049] The four magnetoresistive effect elements 10a, 10b, 10c, and 10d included in the magnetic field detection unit 2 of the magnetic sensor 1 according to an embodiment of the present invention may be provided on the same substrate (one chip). In the present embodiment, the four magnetoresistive effect elements 10a, 10b, 10c, and 10d are provided on the same substrate not shown in the figure, and FIG. 2 is a view of the magnetic field detection unit 2 of the magnetic sensor 1 as seen from the laminated surface (front surface) side of the substrate in the normal direction of the substrate. That is, in FIG. 2, the Z1 side is the front surface side of the substrate, and the Z2 side is the back surface side of the substrate. The Z direction is along the stacking direction of the magnetoresistive effect elements 10a, 10b, 10c, and 10d.

[0050] The magnetic field detection unit 2 includes a first half-bridge circuit in which magnetoresistive effect elements 10a and 10b that both extend in the Y direction are connected in series between a power supply terminal Vdd, which is a power supply feeding point, and a ground terminal GND, and a second half-bridge circuit in which magnetoresistive effect elements 10c and 10d that both extend in the Y direction are connected in series, and has a full-bridge circuit 15 in which the two are connected in parallel.

[0051] The first half-bridge circuit includes an output terminal V1 between the magnetoresistive effect element 10a and the magnetoresistive effect element 10b. The second half-bridge circuit includes an output terminal V2 between the magnetoresistive effect element 10c and the magnetoresistive effect element 10d. The magnitude of the external magnetic field applied from the outside as the measured magnetic field H can be quantitatively measured by the potential difference between the outputs (the midpoint potential Va of the first half-bridge circuit - the midpoint potential Vb of the second half-bridge circuit) from these two output terminals V1 and V2. In the present embodiment, signals including the midpoint potential Va from the output terminal V1 and signals including the midpoint potential Vb from the output terminal V2 are output from the magnetic field detection unit 2, and the processing performed by the magnetic field calculation unit 4 includes calculating the midpoint potential difference using these signals as inputs.

[0052] In the pair of magnetoresistive elements 10a and 10b forming the first half-bridge circuit, the second layer 11 (see Figure 3), which corresponds to the "fixed magnetic layer" of the conventional magnetoresistive element, can maintain its magnetization 11m in a predetermined direction even when subjected to a measurement magnetic field H within the measurement range. Specifically, the magnetization 11m of the second layer 11 is in the X direction X1 (hereinafter abbreviated as "X1 direction"; the same applies to other directions) for the magnetoresistive element 10a, as shown by the white arrows in Figure 2, and in the X2 direction for the magnetoresistive element 10b. Furthermore, in the pair of magnetoresistive elements 10c and 10d forming the second half-bridge circuit, the magnetization 11m of the second layer 11 is in the X2 direction for the magnetoresistive element 10c, as shown by the white arrows in Figure 2, and in the X1 direction for the magnetoresistive element 10d.

[0053] In the first half-bridge circuit and the second half-bridge circuit, the magnetization 11m of the second layer 11 of the magnetoresistive element 10b and magnetoresistive element 10d on the power terminal Vdd side is in opposite directions (antiparallel). Also, the magnetization 11m of the second layer 11 of the magnetoresistive element 10a and magnetoresistive element 10c on the ground terminal GND side is in opposite directions (antiparallel). Therefore, the sensitivity axis direction of the magnetoresistive elements 10a, 10b, 10c, and 10d is the X direction (X1-X2 direction), which is also referred to as the "first direction" in this specification. The Z direction (Z1-Z2 direction) is also referred to as the "second direction," and the Y direction (Y1-Y2 direction) is also referred to as the "third direction."

[0054] In the four magnetoresistive elements 10a, 10b, 10c, and 10d, when no measurement magnetic field H is applied, the magnetization 13m of the first layer 13 (see Figure 3), which corresponds to the "free magnetic layer" of the conventional magnetoresistive element, is aligned in the direction of Y2, as indicated by the black arrow in Figure 2. When the first layer 13 receives a measurement magnetic field H in the first direction (X direction), it can be magnetized in a direction aligned with the measurement magnetic field H. The method for aligning the direction of the magnetization 13m of the first layer 13 when no measurement magnetic field H is applied is not limited. A bias magnetic field or an induced magnetic field may be applied from the outside, or exchange coupling with an antiferromagnetic layer that interacts with the first layer 13 may be used.

[0055] With the above configuration, as the magnitude of the measured magnetic field H in the X direction changes, the outputs from the output terminal V1 of the first half-bridge circuit and the output terminal V2 of the second half-bridge circuit change in opposite directions. Therefore, a large output is obtained as the potential difference (Va - Vb) between the two output terminals V1 and V2. Thus, the magnetic sensor 1 can detect the measured magnetic field H with high precision. In addition, the first half-bridge circuit or the second half-bridge circuit can be used instead of the full-bridge circuit 15, or the magnetoresistive element 10a can be used alone.

[0056] As shown in Figure 2, the magnetic sensor 1 according to this embodiment includes variable magnetic field detection units 100a, 100b, 100c, and 100d that measure the magnetic field H by reversing the magnetization 11m of the second layer 11, that is, by reversing its direction in the same direction, corresponding to the magnetoresistive elements 10a, 10b, 10c, and 10d, respectively. Hereinafter, the variable magnetic field detection unit 100a will be described as a specific example.

[0057] (First Embodiment) Figure 3 is a diagram illustrating an example of a variable magnetic field detection unit provided in a magnetic sensor according to the first embodiment of the present invention. Figure 4 is a diagram illustrating a first state of an example of a variable magnetic field detection unit of a magnetic sensor according to the first embodiment of the present invention. Figure 5 is a diagram illustrating a second state of an example of a variable magnetic field detection unit of a magnetic sensor according to the first embodiment of the present invention.

[0058] The variable magnetic field detection unit 100a includes a magnetoresistive element 10a that exhibits a magnetoresistive effect, having a first layer 13 that can be magnetized in a direction along the measured magnetic field H, a second layer 11 that can maintain a state in which the magnetization 11m is aligned with the first direction (X direction) in Figure 3, and a non-magnetic layer 12 located between the first layer 13 and the second layer 11, and a magnetization control unit 20 that reversibly reverses the magnetization 11m of the second layer 11.

[0059] The components of the magnetoresistive element 10a are stacked in the second direction (Z direction). As described above, the first layer 13 corresponds to the "free magnetic layer" in a conventional magnetoresistive element, and the second layer 11 corresponds to the "fixed magnetic layer" in a conventional magnetoresistive element. By detecting the resistance value caused by the misalignment of the magnetization direction of these layers sandwiching the non-magnetic layer 12, the strength of the measurement magnetic field H applied to the first layer 13 can be measured.

[0060] Unlike the "fixed magnetic layer" of conventional magnetoresistive elements, the second layer 11 of the magnetoresistive element 10a in the variable magnetic field detection unit 100a of the magnetic sensor 1 according to this embodiment maintains a state aligned with a predetermined direction in the first direction even when subjected to a measurement magnetic field H within the measurement range of the magnetoresistive element 10a, but is reversible by the magnetization control unit 20.

[0061] The second layer 11 is constructed using a magnetic material such as a CoFe alloy (cobalt-iron alloy). The non-magnetic layer 12 is an insulating barrier layer made of, for example, MgO, Al2O3, or titanium oxide, when the magnetoresistive element 10a is a tunnel magnetoresistive element (TMR). The first layer 13 is constructed using a soft magnetic material such as a CoFe alloy or NiFe alloy (nickel-iron alloy). The second layer 11 and the first layer 13 may be single-layer or multilayer structures. In the case of a multilayer structure, it is preferable to have a stacked ferri structure. When the magnetoresistive element 10a is a giant magnetoresistive element (GMR), a non-magnetic material such as Cu is used as the constituent material of the non-magnetic layer 12. In this embodiment, the first layer 13 is located on the Z1 side of the magnetoresistive element 10a, and the detection center 10P of the magnetoresistive element 10a is located at the center of the first layer 13.

[0062] In this embodiment, the magnetoresistive element 10a of the variable magnetic field detection unit 100a is, as a specific example, a tunnel magnetoresistive element (TMR). For the purpose of measuring the electrical characteristics of the magnetoresistive element 10a, a measurement wiring 62 is provided so that a voltage from a measurement voltage source V is applied in a second direction (Z direction) between the first layer 13 and the second layer 11 of the magnetoresistive element 10a. In this embodiment, the magnetoresistive element 10a and the magnetization control unit 20 are stacked in the second direction (Z direction), and the magnetization control unit 20 is made of a conductive material. Therefore, the measurement wiring 62 is provided so that a voltage from the measurement voltage source V is applied to the first layer 13 via the magnetization control unit 20.

[0063] In the variable magnetic field detection unit 100a according to this embodiment, the magnetization control unit 20 comprises a spin Hall layer 21 made of a layered body, and an anisotropic variable layer 22 made of a layered body located between the spin Hall layer 21 and the second layer 11, which is magnetically coupled to the second layer 11 and has magnetic anisotropy.

[0064] The spin Hall layer 21 generates a spin-orbit torque when energized, and the magnetization 11m of the second layer 11 is reversed based on the spin-orbit torque from the spin Hall layer 21. In this embodiment, the spin-orbit torque generated in the spin Hall layer 21 affects the anisotropic variable layer 22, and the magnetization 20m of the anisotropic variable layer 22 is aligned in a predetermined direction. Since the anisotropic variable layer 22 is magnetically bonded to the second layer 11, the second layer 11 is magnetized in line with the magnetization 20m of the anisotropic variable layer 22.

[0065] By applying current to the spin Hall layer 21 in the XY plane, the spin Hall effect and the Rashba-Edelstein effect are manifested, imparting spin orbit torque to the anisotropic variable layer 22. The materials constituting the spin Hall layer 21 include heavy metals (5d transition metals) with high specific gravity among paramagnetic transition metals, such as Hf, Ta, W, Pt, and Ir; topological insulators such as BiSb, BiSe, Bi2Se3, and Bi2Te3; and Mn3X (X = Sn, Ge, Ga, RH, Pt, Ir), Mn 1-x Tr xExamples include antiferromagnetic materials such as the gamma phase (Tr = Ni, Fe, Cu, Ru, Pd, Ir, RH, Pd, Pt); and half-Heusler alloy topological semimetals made of mixed crystals of these materials, such as LuPtSb, LuPdBi, LuPtBi, ScPtBi, YAuPb, LaPtBi, CePtBi, THPtPb, and LaAuPb.

[0066] In one specific example shown in Figure 3, the spin Hall layer 21 is a film-like structure, which may be a single structure, i.e., a single layer film, or a multilayer film. If it is a multilayer film, boundary regions may be formed between adjacent films. The spin Hall layer 21 may be composed entirely of a single material, or of multiple materials. If it is composed of multiple materials, it may have a multilayer structure as described above, or it may have a dispersed structure. If it has a dispersed structure, the degree of dispersion is arbitrary, and it may be a structure in which nanocrystals are dispersed, or a certain pattern may be formed. Furthermore, a compositional distribution may be set in the spin Hall layer 21.

[0067] The anisotropic variable layer 22 can have its magnetization 20m reversibly reversed based on the spin-orbit torque from the spin Hall layer 21. Furthermore, since the anisotropic variable layer 22 is magnetically coupled to the second layer 11 of the magnetoresistive element 10a, the magnetization 11m of the second layer 11 will be reversed based on the spin-orbit torque from the spin Hall layer 21. The anisotropic variable layer 22, like the spin Hall layer 21, may be composed of a single material or of multiple materials. If it is composed of multiple materials, it may have a dispersed structure or a compositional distribution may be set in the anisotropic variable layer 22.

[0068] The anisotropic variable layer 22 may be composed of any material as long as it performs this magnetization reversal function. Like the second layer 11, it may be composed of a ferromagnetic material or an antiferromagnetic material. Specific examples of antiferromagnetic materials include at least a part of the material that constitutes the spin Hall layer 21 described above. When the anisotropic variable layer 22 contains an antiferromagnetic material, a magnetic field may be generated inside the anisotropic variable layer 22 based on physical phenomena different from those that occur when the anisotropic variable layer 22 contains a ferromagnetic material (for example, a virtual magnetic field). Therefore, in this specification, the concept of "magnetization" in relation to the anisotropic variable layer 22, etc., also includes the generation of a magnetic field inside the anisotropic variable layer 22 based on physical phenomena different from those that occur when the anisotropic variable layer 22 contains a ferromagnetic material.

[0069] (First State) The first state shown in Figure 4 is the state in which the variable magnetic field detection unit 100a outputs a first output. In this example, the control wiring 61 is provided so that the current from the control current source I (control current 20c) is applied to the spin Hall layer 21 in the X1-X2 direction.

[0070] In the first state, the control current 20c for the spin Hall layer 21 of the variable magnetic field detection unit 100a is set to the X2 direction, and the magnetization 11m of the second layer 11 is set to the X1 direction. Note that the magnetization 11m of the second layer 11 is shown by a white arrow in Figure 2. The current flowing through the spin Hall layer 21 generates a spin current 20s1 in the Z direction in the spin Hall layer 21, and spins oriented in a predetermined direction are injected into the anisotropic variable layer 22 from the Z direction Z1 side of the spin Hall layer 21. Due to the spin orbit torque based on these injected spins, the magnetization 20m of the anisotropic variable layer 22 is set to the X1 direction. From the viewpoint of improving the controllability of the direction of the magnetization 20m of the anisotropic variable layer 22 due to these injected spins, it is sometimes preferable that a magnetic field in the Z direction (second direction) is applied to the magnetization control unit 20. The method of applying the magnetic field is not limited, and specific examples include placing a permanent magnet or electromagnet near the variable magnetic field detection unit 100a, and providing an antiferromagnetic material capable of generating a magnetic field based on exchange coupling.

[0071] Since the anisotropic variable layer 22 and the second layer 11 are magnetically coupled, the magnetization 11m of the second layer 11 is also oriented towards X1.

[0072] Therefore, in the first state, the magnetization 11m of the second layer 11 of the magnetoresistive element 10a is fixed in the direction of X1. In this state, the variable magnetic field detection unit 100a measures the measurement magnetic field H, and the first output is output.

[0073] (Second State) The second state shown in Figure 5 is the state in which a second output is output from the variable magnetic field detection unit 100a. In the second state, the control current 20c for the spin Hall layer 21 of the variable magnetic field detection unit 100a is directed towards X1, and the magnetization 11m of the second layer 11 is directed towards X2. The spin current 20s2 generated in the spin Hall layer 21 by this current has the spin orientation reversed from the spin current 20s1 shown in Figure 4. Therefore, the spins injected from the spin Hall layer 21 into the anisotropic variable layer 22 are oriented in the opposite direction to that of the first state. Consequently, the magnetization 20m of the anisotropic variable layer 22, which is oriented by the spin orbit torque based on the injected spins, is in the opposite direction (X2 direction) to that of the first state. In other words, the reversal of the control current 20c for the spin Hall layer 21 causes a reversal of the magnetization of the anisotropic variable layer 22. Furthermore, since the anisotropic variable layer 22 and the second layer 11 are magnetically coupled, the magnetization 11m of the second layer 11 is also oriented towards X2.

[0074] Therefore, in the second state, the magnetization 11m of the second layer 11 of the magnetoresistive element 10a is fixed in the direction of X2. In this state, the variable magnetic field detection unit 100a measures the measurement magnetic field H, and a second output is output.

[0075] (First Measurement Method) Figure 6 is a flowchart illustrating a first measurement method using a magnetic sensor according to the first embodiment of the present invention. In the first measurement method, as shown in Figure 6, first, as a first measurement step, a control signal output from the control unit 7 causes the control power supply 3 to output a signal to set the variable magnetic field detection units 100a, 100b, 100c, and 100d of the magnetic field detection unit 2 to a first state. Specifically, the direction of the current flowing through the spin Hall layer 21 of the magnetization control unit 20 is set to a predetermined direction. In the magnetic field detection unit 2 shown in Figure 2, the direction of the magnetization 11m of the second layer 11 of the two magnetoresistive effect elements 10b and 10c in the first state and the two magnetoresistive effect elements 10a and 10d in the second state is indicated by white arrows.

[0076] Thus, with the variable magnetic field detection units 100a, 100b, 100c, and 100d in a first or second state, the magnetic field H is measured using the magnetoresistive elements 10a, 10b, 10c, and 10d, and outputs are obtained from each of the variable magnetic field detection units 100a, 100b, 100c, and 100d. Based on these outputs, the magnetic field detection unit 2 outputs a signal as a first signal, which includes the midpoint potential difference, which is the difference between the midpoint potential Va from output terminal V1 and the midpoint potential Vb from output terminal V2 (step S101). These signals including the midpoint potential difference output from the magnetic field detection unit 2 are input to the magnetic field calculation unit 4, and data indicating these signals is stored in the magnetic field calculation unit 4 or a memory (not shown). Note that the first signal may also include the midpoint potential Va and the midpoint potential Vb. In this case, data indicating the two midpoint potentials is stored in the magnetic field calculation unit 4 or a memory (not shown).

[0077] Next, as a second measurement step, a control signal output from the control unit 7 causes the control power supply 3 to output a signal to set the variable magnetic field detection units 100a, 100b, 100c, and 100d of the magnetic field detection unit 2 to a second state. Specifically, the direction of the current flowing through the spin Hall layer 21 of the magnetization control unit 20 is set to the opposite direction to that of the first state. Figure 7 is an explanatory diagram of the magnetic field detection unit of a magnetic sensor according to one embodiment of the present invention. In the magnetic field detection unit 2 shown in Figure 7, the direction of the magnetization 11m of the second layer 11 of the two magnetoresistive effect elements 10a and 10d in the first state and the two magnetoresistive effect elements 10b and 10c in the second state is indicated by white arrows, and these magnetizations are in the opposite direction to when the first signal is output. To explain using the variable magnetic field detection unit 100a as a specific example, when it outputs a first signal, i.e., in the first state, the direction of the magnetization 11m is towards X1, as shown in Figures 2 and 4, and when it outputs a second signal, i.e., in the second state, the direction of the magnetization 11m is towards X2, as shown in Figures 5 and 7.

[0078] Thus, with the variable magnetic field detection units 100a, 100b, 100c, and 100d in a first or second state, the magnetic field H is measured using the magnetoresistive elements 10a, 10b, 10c, and 10d, and outputs are obtained from each of the variable magnetic field detection units 100a, 100b, 100c, and 100d. Based on these signals, the magnetic field detection unit 2 outputs a second signal, which includes the midpoint potential Va from output terminal V1 and the midpoint potential Vb from output terminal V2, or a signal of the difference between these midpoint potentials (step S102). The measurement time for both steps S101 and S102 is sufficiently shorter than 1 microsecond (e.g., 0.01 microseconds), and the time required for steps S101 and S102 is also sufficiently shorter than 1 microsecond (e.g., 0.03 microseconds). Therefore, steps S101 and S102 are performed in an environment where the 1 / f noise is substantially equal, and the 1 / f noise contained in the first signal and the 1 / f noise contained in the second signal 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 a memory (not shown) as data representing those signals, or as data representing the midpoint potential difference signal which is the difference between the two signals.

[0079] Next, the magnetic field calculation unit 4 reads the data stored in the magnetic field calculation unit 4 or a memory (not shown) in steps S101 and S102, and performs a magnetic field calculation step in which it calculates the difference between the midpoint potential indicated by the first signal and the midpoint potential indicated by the second signal (step S103). If the data stored in the magnetic field calculation unit 4 or a memory (not shown) includes two midpoint potentials as data related to the first signal and two midpoint potentials as data related to the second signal, the magnetic field calculation unit 4 obtains a signal including the midpoint potential difference from the data related to the first signal, obtains a signal including the midpoint potential difference from the data related to the second signal, and further performs a magnetic field calculation step in which it calculates the difference between these two signals including the midpoint potential difference.

[0080] The magnetic field calculation unit 4 performs the above processing to obtain a measurement signal from which 1 / f noise has been appropriately removed. This 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 measurement method using the magnetic sensor 1 according to this embodiment has 1 / f noise appropriately removed, and thus has a higher resolution (magnetic resolution) of the signal based on the measured magnetic field H than the signal based on the first output (a signal including the midpoint potential difference of the first state) or the signal based on the second output (a signal including the midpoint potential difference of the second state).

[0081] In this embodiment, since the magnetic field detection unit 2 has a full-bridge circuit 15, the signals that the magnetic field calculation unit 4 processes for difference are the signal of the midpoint potential difference of the first state based on the first output and the signal of the midpoint potential difference of the second state based on the second output. However, the signals that the magnetic field calculation unit 4 processes are set appropriately according to the output signals 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 calculate the difference between the first output (first signal) and the second output (second signal) from the variable magnetic field detection unit 100a.

[0082] (Another example of the first embodiment) Figure 8 is a diagram illustrating another example of the variable magnetic field detection unit of the magnetic sensor according to the first embodiment of the present invention. Figure 9 is a diagram illustrating the first state of another example of the variable magnetic field detection unit of the magnetic sensor according to the first embodiment of the present invention. Figure 10 is a diagram illustrating the second state of another example of the variable magnetic field detection unit of the magnetic sensor according to the first embodiment of the present invention.

[0083] In the example shown in Figure 8, in contrast to the example shown in Figure 3, the control wiring 61 is provided so that the current from the control current source I is applied to the spin Hall layer 21 in the Y direction. In the first state, as shown in Figure 9, the control current 20c is in the Y1 direction, and based on the spin current 20s1 generated by this, the magnetization 20m of the anisotropic variable layer 22 is in the X1 direction. Since the anisotropic variable layer 22 and the second layer 11 are magnetically coupled, in the first state, the magnetization 11m of the second layer 11 is "fixed" in the X1 direction. On the other hand, in the second state, as shown in Figure 10, the control current 20c is in the Y2 direction, and based on the spin current 20s2 generated by this, the magnetization 20m of the anisotropic variable layer 22 is in the X2 direction, which is the opposite direction to the first state. Since the anisotropic variable layer 22 and the second layer 11 are magnetically coupled, in the second state, the magnetization 11m of the second layer 11 is "fixed" in the direction of X2.

[0084] (Modified Version of the First Embodiment) Figure 11 is a diagram illustrating a modified version of the variable magnetic field detection unit provided in the magnetic sensor according to the first embodiment of the present invention. In the example shown in Figure 3, the magnetization control unit 20 had a spin Hall layer 21 and an anisotropic variable layer 22. However, in the modified version of the variable magnetic field detection unit 100a shown in Figure 11, the magnetization control unit 20 is an integrated unit consisting of an electromagnetically driven magnetization control unit 201 that can reversibly reverse magnetization by energizing. In this case, control wiring 61 is connected to the electromagnetically driven magnetization control unit 201, and a current from a control current source I flows to the electromagnetically driven magnetization control unit 201, generating a spin current 20s1, which sets the direction of the magnetization 20m of the electromagnetically driven magnetization control unit 201 to a predetermined direction (X1 direction in Figure 11). As a result, the direction of the magnetization 11m of the second layer 11 which is magnetically coupled with the electromagnetically driven magnetization control unit 201 is also fixed to the X1 direction. The electromagnetically driven magnetization control unit 201 is not limited to having a uniform structure, and may have structural non-uniformity such as a laminated structure or a dispersed structure.

[0085] (Second Embodiment) Figure 12 is a diagram illustrating an example of a variable magnetic field detection unit provided in a magnetic sensor according to the second embodiment of the present invention. The variable magnetic field detection unit 100a of the magnetic sensor 1 according to the second embodiment of the present invention differs from the variable magnetic field detection unit 100a of the magnetic sensor 1 according to the first embodiment in that it combines the functions of the second layer 11 and the anisotropic variable layer 22 of the variable magnetic field detection unit 100a of the magnetic sensor 1, and has a variable second layer 111 that has a portion that can be reversibly reversibly magnetized based on the spin orbit torque from the spin Hall layer 21. In other words, in the variable magnetic field detection unit 100a of the magnetic sensor 1 according to the second embodiment of the present invention, the second layer 11 of the variable magnetic field detection unit 100a of the magnetic sensor 1 according to the first embodiment is the variable second layer 111, and the magnetization control unit 20 has a spin Hall layer 21 but does not have an anisotropic variable layer 22.

[0086] The material constituting the variable second layer 111 is not particularly limited as long as it is a material whose magnetization can be reversibly reversed by the spin-orbit torque from the spin Hall layer 21, and the variable second layer 111 may have a portion made of an antiferromagnetic material, as exemplified as the constituent material of the anisotropic variable layer 22. The variable second layer 111 may have a homogeneous structure, or it may have a laminated structure or a dispersed structure of portions made of different materials. Furthermore, the variable second layer 111 may have a heterogeneous structure in which its composition changes continuously or stepwise.

[0087] The control method for the first and second states in the variable magnetic field detection unit 100a of the magnetic sensor 1 according to the second embodiment of the present invention is the same as in the case of the variable magnetic field detection unit 100a of the magnetic sensor 1 according to the first embodiment. That is, the wiring of the control current source I is connected to the spin Hall layer 21, and the direction of the magnetization 111m of the variable second layer 111 is set by the direction of the control current 20c flowing through the spin Hall layer 21. Therefore, by flowing the control currents 20c in opposite directions, a first output, which is the output of the variable magnetic field detection unit 100a in the first state, and a second output, which is the output of the variable magnetic field detection unit 100a in the second state, can be obtained. Note that in Figure 12, the first state is shown, similar to Figure 4. In Figure 12, the control wiring 61 is provided so that the control current 20c applied to the spin Hall layer 21 is in the direction of X1 or X2, but it is not limited to this, and the control wiring 61 may be provided so that the control current 20c is in the direction of Y1 or Y2.

[0088] (Third Embodiment) Figure 13 is a diagram illustrating an example of a variable magnetic field detection unit provided in a magnetic sensor according to the third embodiment of the present invention. The variable magnetic field detection unit 100a of the magnetic sensor 1 according to the third embodiment of the present invention differs from the variable magnetic field detection unit 100a of the magnetic sensor 1 according to the first embodiment in that it combines the functions of the second layer 11 and the magnetization control unit 20 of the variable magnetic field detection unit 100a of the magnetic sensor 1 according to the first embodiment. In other words, the second layer 11 and the magnetization control unit 20 are integrated, and the variable energized second layer 112 has a portion that generates a spin orbit torque internally by current from the control wiring 61, allowing for reversible magnetization reversal.

[0089] The material constituting the variable current-conductivity second layer 112 is not particularly limited as long as it is a material whose magnetization can be reversed according to the direction of current flow, and the variable current-conductivity second layer 112 may have a portion made of an antiferromagnetic material, as exemplified as the constituent material of the anisotropic variable layer 22. The variable current-conductivity second layer 112 may have a homogeneous structure, or it may have a laminated structure or dispersed structure of portions made of different materials. Furthermore, the variable current-conductivity second layer 112 may have a heterogeneous structure in which its composition changes continuously or in steps.

[0090] The control method for the first and second states in the variable magnetic field detection unit 100a of the magnetic sensor 1 according to the third embodiment of the present invention is substantially the same as that for the variable magnetic field detection unit 100a of the magnetic sensor 1 according to the first embodiment. That is, the wiring of the control current source I is connected to the variable energized second layer 112 instead of the spin Hall layer 21 in the first embodiment, and the direction of the magnetization 112m of the variable energized second layer 112 is set by the direction of the control current 20c that flows through the variable energized second layer 112. Therefore, by flowing the control currents 20c in opposite directions, the first output, which is the output of the variable magnetic field detection unit 100a in the first state, and the second output, which is the output of the variable magnetic field detection unit 100a in the second state, can be obtained. Note that Figure 13 shows the first state, similar to Figure 9. In Figure 13, the control wiring 61 is provided so that the control current 20c applied to the spin Hall layer 21 is directed towards Y1 or Y2, but it is not limited to this, and the control wiring 61 may be provided so that the control current 20c is directed towards X1 or X2. The variable current second layer 112 has a junction between an antiferromagnetic material and a ferromagnetic material, and the exchange coupling that occurs at this junction may serve as the second layer bias magnetic field source.

[0091] (Second Measurement Method) Figure 14 is a diagram illustrating a second measurement method (first state) using a magnetic sensor according to the first embodiment of the present invention. Figure 15 is a diagram illustrating a second measurement method (second state) using a magnetic sensor according to the first embodiment of the present invention. In the second measurement method, the flowchart of the measurement method is the same as the flowchart of the first measurement method shown in Figure 6, but the configuration of the magnetic field detection unit 2A provided in the magnetic sensor 1 is different.

[0092] In the second measurement method, as shown in Figure 14, the magnetic field detection unit 2A has a half-bridge circuit 16. The half-bridge circuit 16 has two variable magnetic field detection units. That is, the half-bridge circuit 16 has a first variable magnetic field detection unit 101 and a second variable magnetic field detection unit 102 connected in series, and an output unit VA that outputs an electrical signal relating to the potential between the first variable magnetic field detection unit 101 and the second variable magnetic field detection unit 102 connected in series. The first variable magnetic field detection unit 101 and the second variable magnetic field detection unit 102 are controlled so that the second layer 11 is magnetized in opposite directions. In Figure 14, as shown by the white arrows, the magnetization 11m of the second layer 11 of the first variable magnetic field detection unit 101 is in the direction of X2, and the magnetization 11m of the second layer 11 of the second variable magnetic field detection unit 102 is in the direction of X1. The first layers 13 of both the first variable magnetic field detection unit 101 and the second variable magnetic field detection unit 102 are set to align in the same direction when not subjected to the measurement magnetic field H. In Figure 14, as shown by the black arrows, the magnetization 13m of the first layer 13 is set to the Y2 direction when not subjected to the measurement magnetic field H. The magnetization direction of the first layer 13 can be set by a bias magnetic field source (permanent magnet, inductive magnetic field source, structure that generates exchange coupling) not shown.

[0093] The magnetic field calculation unit 4 takes the electrical signal from the output unit VA as input and performs calculation processing to calculate the measured magnetic field H. This calculation processing includes determining the difference between a first electrical signal output from the output unit VA when the magnetization 11m of the second layer 11 of the first variable magnetic field detection unit 101 is in a first state which is unidirectional in the first direction, and a second electrical signal output from the output unit VA when the magnetization 11m of the second layer 11 of the first variable magnetic field detection unit 101 is in a second state which is unidirectional in the first direction.

[0094] Specifically, as the first measurement step, a control signal output from the control unit 7 causes the control power supply 3 to output a signal to set the first variable magnetic field detection unit 101 and the second variable magnetic field detection unit 102 of the magnetic field detection unit 2A to a first state. Specifically, the direction of the current flowing through the spin Hall layer 21 of the magnetization control unit 20 is set to a predetermined direction. In Figure 14, the direction of the magnetization 11m of the second layer 11 of the first variable magnetic field detection unit 101 and the second variable magnetic field detection unit 102 in the first state is indicated by a white arrow.

[0095] Thus, with the first variable magnetic field detection unit 101 and the second variable magnetic field detection unit 102 in the first state, the first variable magnetic field detection unit 101 and the second variable magnetic field detection unit 102 measure the magnetic field H, and a first electrical signal is obtained from the output unit VA (step S101). The first electrical signal is input to the magnetic field calculation unit 4 and stored in the magnetic field calculation unit 4 or a memory (not shown).

[0096] Next, as a second measurement step, a control signal output from the control unit 7 causes the control power supply 3 to output a signal to set the first variable magnetic field detection unit 101 and the second variable magnetic field detection unit 102 of the magnetic field detection unit 2A to a second state. Specifically, the direction of the current flowing through the spin Hall layer 21 of the magnetization control unit 20 is set to the opposite direction to that of the first state. Figure 15 is an explanatory diagram (second state) of the magnetic field detection unit of a magnetic sensor according to one embodiment of the present invention. In Figure 15, the direction of the magnetization 11m of the second layer 11 of the first variable magnetic field detection unit 101 and the second variable magnetic field detection unit 102 in the second state is indicated by white arrows, and these magnetizations 11m are in the opposite direction to those in the first state.

[0097] Thus, the first variable magnetic field detection unit 101 and the second variable magnetic field detection unit 102 are set to the second state, and the first variable magnetic field detection unit 101 and the second variable magnetic field detection unit 102 measure the magnetic field H, and a second electrical signal is obtained from the output unit VA (step S102). The second electrical signal is input to the magnetic field calculation unit 4 and stored in the magnetic field calculation unit 4 or a memory (not shown).

[0098] Next, the magnetic field calculation unit 4 performs a process to determine the difference between the first electrical signal and the second electrical signal stored in the magnetic field calculation unit 4 or a memory (not shown) in steps S101 and S102, as a magnetic field calculation step (step S103). By performing the above process, the magnetic field calculation unit 4 can obtain the measurement signal obtained from the full-bridge circuit 15 using the half-bridge circuit 16. Therefore, the magnetic field detection unit 2A of the second measurement method can be made smaller in area compared to the case where the first measurement method is used with a magnetic field detection unit 2 having a full-bridge circuit 15.

[0099] Furthermore, in the full-bridge circuit 15, an ideal output can be obtained when the electrical characteristics of the four magnetoresistive elements 10a, 10b, 10c, and 10d are exactly the same. However, in reality, since the four elements are manufactured from different sources, differences in their electrical characteristics are unavoidable, and these differences contribute to a decrease in the measurement accuracy of the full-bridge circuit 15. In contrast, in the second measurement method, the number of elements used for measurement is halved compared to the full-bridge circuit 15, thus suppressing the decrease in measurement accuracy caused by variations in the electrical characteristics of the elements. Therefore, by combining the second measurement method and the first measurement method, it is possible to particularly improve the magnetic resolution of the magnetic sensor 1.

[0100] Figure 16 is a detailed explanatory diagram of the state shown in Figure 3 (non-energized control state). In the state shown in Figure 16, the control unit 7 controls the system so that no control current 20c flows from the control current source I to the spin Hall layer 21. As a result, the magnetization control unit 20 of the variable magnetic field detection unit 100a of the magnetic field detection unit 2 controls the system so that no spin orbit torque is generated from the spin Hall layer 21.

[0101] In this specific example, the spin Hall layer 21 has a portion made of antiferromagnetic material. Therefore, when spin orbit torque is not generated, the magnetic field caused by the exchange coupling 21af between this antiferromagnetic portion and the anisotropic variable layer 22 acts as a bias magnetic field, generating a magnetization 22m in the Y2 direction in the anisotropic variable layer 22. Since the anisotropic variable layer 22 and the second layer 11 are magnetically coupled, a magnetization 11m in the Y2 direction is also generated in the second layer 11. In other words, the exchange coupling 21af based on the antiferromagnetic portion (antiferromagnetic part) in the spin Hall layer 21 is a bias magnetic field source for the second layer, and when spin orbit torque is not generated from the spin Hall layer 21 due to the control current source I not supplying the control current 20c, it exerts a bias magnetic field on the second layer 11.

[0102] As shown in Figure 16, when the control unit 7 performs control that prevents the flow of control current 20c from the control current source I, the magnetization control unit 20 enters a de-energized state, and the magnetization 11m of the second layer 11 is maintained in the Y2 direction, which is the first orientation (the orientation along the first orthogonal direction (Y1-Y2 direction), which is one of the directions perpendicular to the stacking direction (Z1-Z2 direction) in which the first layer 13 and the second layer 11 are aligned). In the de-energized state, the variable magnetic field detection unit 100a has no measurement sensitivity (no sensitivity) to the measurement magnetic field H in the X direction, but has measurement sensitivity to the measurement magnetic field H' in the Y direction. Therefore, when the second layer 11 is in the de-energized state, the variable magnetic field detection unit 100a uses the Y direction as its sensitivity axis.

[0103] In contrast, as shown in Figures 4 and 5, when the control unit 7 controls the flow of a control current 20c from the control current source I to the spin Hall layer 21, the magnetization control unit 20 enters an energized state, and the magnetization 11m of the second layer 11 is maintained in an energized control state in the X1 direction (Figure 4) or X2 direction (Figure 5), which is a second orientation (along the second orthogonal direction (X1-X2 direction) that is perpendicular to the stacking direction (Z1-Z2 direction) and intersects the first orthogonal direction (Y1-Y2 direction)). In the energized control state, the variable magnetic field detection unit 100a has measurement sensitivity to the measurement magnetic field H in the X direction. Therefore, when the second layer 11 is in the energized control state, the variable magnetic field detection unit 100a uses the X direction as its sensitivity axis.

[0104] Figure 17 is a flowchart illustrating a third measurement method using a magnetic sensor according to the first embodiment of the present invention. In the third measurement method, as shown in Figure 17, first, in the magnetic sensor 1, as the first measurement step, a control signal output from the control unit 7 causes the control power supply 3 to output a signal to put the second layer 11 of the variable magnetic field detection unit 100a of the magnetic field detection unit 2 into a non-energized state. Specifically, the control current 20c is not supplied to the spin Hall layer 21 of the magnetization control unit 20.

[0105] In this way, the second layer 11 of the variable magnetic field detection unit 100a is set to a non-energized state, and the magnetoresistive element 10a measures the magnetic field H' along the Y direction, causing the variable magnetic field detection unit 100a to output a first output (step S111). The first signal output from the variable magnetic field detection unit 100a is input to the magnetic field calculation unit 4, and data indicating the first signal is stored in the magnetic field calculation unit 4 or a memory (not shown).

[0106] Next, as the second measurement step, a control signal output from the control unit 7 causes the control power supply 3 to output a signal to energize the second layer 11 of the variable magnetic field detection unit 100a of the magnetic field detection unit 2. Specifically, a control current 20c is supplied to the spin Hall layer 21 of the magnetization control unit 20.

[0107] In this way, the second layer 11 of the variable magnetic field detection unit 100a is set to an energized state, and the magnetoresistive element 10a measures the magnetic field H along the X direction, causing the variable magnetic field detection unit 100a to output a second output (step S112). The second signal output from the magnetic field detection unit 2 is input to the magnetic field calculation unit 4, and data indicating the second signal is stored in the magnetic field calculation unit 4 or a memory (not shown).

[0108] The measurement times for both step S111 and step S112 are both well less than 1 microsecond (e.g., 0.01 microseconds), and the time required for both step S111 and step S112 is also well less than 1 microsecond (e.g., 0.03 microseconds). Therefore, step S111 and step S112 measure substantially the same measurement magnetic field applied to the variable magnetic field detection unit 100a, where the measurement magnetic field H' is the Y-direction component of the measurement magnetic field applied to the variable magnetic field detection unit 100a, and the measurement magnetic field H is its X-direction component.

[0109] Next, the magnetic field calculation unit 4 reads the data stored in the magnetic field calculation unit 4 or a memory (not shown) in steps S111 and S112, and performs a magnetic field calculation step (step S113) to determine the actual measured magnetic field from the first output and the second output. In the magnetic field calculation step, either the strength of the actual measured magnetic field or the direction of the actual measured magnetic field may be determined. When determining the direction of the measured magnetic field, for example, the relative angle in the XY plane may be determined based on the first direction (Y2 direction) measured in the non-energized state.

[0110] Figure 18 is a diagram illustrating in detail an example (modified version) of a variable magnetic field detection unit provided in a magnetic sensor according to the first embodiment of the present invention. In the configuration shown in Figure 16, the anisotropic variable layer 22 has a portion made of antiferromagnetic material (antiferromagnetic portion), and the exchange coupling 21af based on this antiferromagnetic portion was a second layer bias magnetic field source that exerted a bias magnetic field on the second layer 11. However, in the configuration shown in Figure 18, the exchange coupling 22af based on the portion made of antiferromagnetic material (antiferromagnetic portion) in the anisotropic variable layer 22 is a second layer bias magnetic field source that exerts a bias magnetic field on the second layer 11. Specifically, when the control unit 7 performs control that does not flow the control current 20c from the control current source I, the exchange coupling 22af based on the antiferromagnetic portion of the anisotropic variable layer 22 generates magnetization 11m in the Z1 direction in the second layer 11. Therefore, in this modified example, when the second layer 11 is in a non-energized control state, the variable magnetic field detection unit 100a has the Z direction as its sensitivity axis and can measure the measured magnetic field H'' in the Z direction. Thus, in this modified example, in a specific example, the relative angle in the YZ plane can be determined with reference to the first direction (Y2 direction) measured in the non-energized control state.

[0111] If the magnetic field detection unit 2 has a variable magnetic field detection unit 100a with the configuration shown in Figure 16 and a variable magnetic field detection unit 100a with the configuration shown in Figure 18 (for example, as a variable magnetic field detection unit 100b), then the magnetic field calculation unit 4 can determine the three-dimensional orientation of the actually applied measured magnetic field (for example, the three-dimensional relative angle with respect to the first orientation (Y2 direction) related to the variable magnetic field detection unit 100a). In the conventional technology, three magnetic field detection elements are required to determine the three-dimensional orientation of the measured magnetic field, with the X, Y, and Z directions as the sensitivity axes, respectively. However, with the above configuration, the three-dimensional orientation can be measured with two variable magnetic field detection units 100a and 100b. Moreover, since both the two variable magnetic field detection units 100a and 100b measure the same unidirectional component (X direction in this example) of the measured magnetic field, the relative angle correction of the two variable magnetic field detection units 100a and 100b can be performed based on these results. Therefore, the magnetic sensor 1 in this example can perform angle measurement with higher accuracy than conventional magnetic sensors.

[0112] The embodiments described above are provided to facilitate understanding of the present invention and are not intended to limit it. Therefore, each element disclosed in the above embodiments is intended to include all design changes and equivalents that fall within the technical scope of the present invention. For example, in the above description, the magnetization control unit 20 generates a spin-orbit torque to reverse the magnetization 11m of the second layer 11, but is not limited to this, and the magnetization 11m of the second layer 11 may also be reversed by a spin-transfer torque, and both the spin-orbit torque and the spin-transfer torque may contribute to the reversal of the magnetization 11m of the second layer 11. In particular, in a variable second layer 111 or an energized variable second layer 112 that combines the functions of the second layer 11 and at least some of the functions of the magnetization control unit 20, both the spin-orbit torque and the spin-transfer torque tend to contribute to the reversal of the magnetization 11m of the second layer 11.

[0113] In the configuration shown in Figure 16, the spin Hall layer 21 has a portion made of antiferromagnetic material. When no spin orbit torque is generated in the spin Hall layer 21, the magnetic field caused by the exchange coupling 21af between this antiferromagnetic portion and the anisotropic variable layer 22 acts as a bias magnetic field, generating magnetization 22m in the Y2 direction in the anisotropic variable layer 22. In this configuration, the spin Hall layer 21 may be made of antiferromagnetic material, or it may have a laminated structure of a non-magnetic layer and an antiferromagnetic layer.

[0114] The second layer bias magnetic field source, which generates a Y2-oriented magnetization 22m in the anisotropic variable layer 22 when no spin orbit torque is generated in the spin Hall layer 21, thereby generating a Y2-oriented magnetization 11m in the second layer 11, is not limited to the exchange coupling 21af. The anisotropic variable layer 22 may have a portion made of antiferromagnetic material (antiferromagnetic portion), and a magnetic portion in contact with the antiferromagnetic portion, where the portion is made of ferromagnetic material or antiferromagnetic material, and the exchange coupling 22af generated between the antiferromagnetic portion and the magnetic portion may serve as the second layer bias magnetic field source. Figure 19 shows one specific example of a second layer bias magnetic field source. In Figure 19, the anisotropic variable layer 22 has a laminated structure consisting of an antiferromagnetic layer 221, which is an antiferromagnetic portion close to the spin Hall layer 21, and a magnetic layer 222, which is a magnetic portion close to the second layer 11. Due to the exchange coupling 22af between the antiferromagnetic layer 221 and the magnetic layer 222, magnetization 222m in the Y2 direction is generated in the magnetic layer 222, and as a result, magnetization 11m in the Y2 direction is also generated in the second layer 11.

[0115] The second layer bias magnetic field source is not limited to exchange coupling. The second layer bias magnetic field source may include, for example, at least one of a coil that generates an induced magnetic field by current and a permanent magnet. Figure 20 shows another specific example of the second layer bias magnetic field source, and Figure 21 is a cross-sectional view taken along line B-B' of Figure 20. In Figure 20, a laminate of a magnetoresistive element 10a having a second layer 11 and a magnetization control unit 20, and a second layer bias magnetic field source consisting of permanent magnets 71 and 72 are arranged in the Y1-Y2 direction, which intersects the Z1-Z2 direction, which is the lamination direction of the first layer 13 and the second layer 11. In one example, the spin Hall layer 21 is made of a non-magnetic material and the anisotropy variable layer 22 is made of a ferromagnetic material, so the magnetization control unit 20 is not provided with any special configuration to generate exchange coupling. However, since the magnetization 71m of the permanent magnet 71 and the magnetization 72m of the permanent magnet 72 are both oriented in Y2, as shown in Figures 20 and 21, the magnetization 11m of the second layer 11 and the magnetization 22m of the anisotropic variable layer 22 are both oriented in Y2.

[0116] Figure 22 shows another specific example of a second-layer bias magnetic field source. The structure shown in Figure 22 corresponds to the structure shown in Figure 20 with the permanent magnets 71 and 72 removed. In this structure, the second-layer bias magnetic field source is the shape magnetic anisotropy of the anisotropic variable layer 22. As shown in Figure 22, the magnetization control unit 20 has a shape that is longer in the Y1-Y2 direction than in the X1-X2 direction, so shape magnetic anisotropy occurs in the anisotropic variable layer 22, and its magnetization 22m is aligned in the Y1-Y2 direction. In Figure 22, as one specific example, the magnetization 22m is aligned in the Y2 direction by forming the anisotropic variable layer 22 by deposition in a magnetic field. As a result, the magnetization 11m of the second layer 11 is also aligned in the Y2 direction. Other specific examples of a second-layer bias magnetic field source that aligns the magnetization 11m in the Y2 direction include the inverse magnetostrictive effect of the anisotropic variable layer 22 and the uniaxial crystal magnetic anisotropy.

[0117] Figure 23 shows yet another specific example of a second-layer bias magnetic field source. In contrast to the structure shown in Figure 16, the structure shown in Figure 23 does not have any special configuration in the magnetization control unit 20 to generate exchange coupling. Specifically, the spin Hall layer 21 is made of a non-magnetic material, and the anisotropic variable layer 22 is made of a ferromagnetic material, but a permanent magnet layer 70 is laminated on the Z2 side of the spin Hall layer 21. That is, the second-layer bias magnetic field source, which consists of the permanent magnet layer 70, and the second layer 11 are aligned in the Z1-Z2 direction, which is the lamination direction of the first layer 13 and the second layer 11. The magnetization 70m of the permanent magnet layer 70 is oriented in the Y1 direction, and due to the magnetic field from this permanent magnet layer 70, the magnetization 11m of the second layer 11 and the magnetization 22m of the anisotropic variable layer 22 are both aligned in the Y2 direction.

[0118] Figure 24 shows yet another specific example of a second-layer bias magnetic field source. In the variable magnetic field detection unit 100a shown in Figure 24, the anisotropic variable layer 22 has uniaxial crystalline magnetic anisotropy in the Z1-Z2 direction, and the magnetization 22m based on this crystalline magnetic anisotropy acts as a second-layer bias magnetic field source, causing the magnetization 11m of the second layer 11 to be aligned in the Z1-Z2 direction. The method for imparting uniaxial crystalline magnetic anisotropy in the Z1-Z2 direction to the anisotropic variable layer 22 is arbitrary; for example, the magnetization 22m can be directed towards Z1 by forming the anisotropic variable layer 22 by deposition in a magnetic field.

[0119] The second layer bias magnetic field source that directs the magnetization 11m of the second layer 11 towards Z1 is not limited to the uniaxial crystalline magnetic anisotropy of the anisotropic variable layer 22. For example, as shown in Figure 19, the anisotropic variable layer 22 may have a portion made of antiferromagnetic material, and the exchange coupling 22af involving this portion may become the second layer bias magnetic field source that directs the magnetization 11m towards Z1. Furthermore, the magnetization 11m can also be directed towards Z1 by a configuration in which the second layer bias magnetic field source, consisting of permanent magnets 71, 72 or electromagnets, and the second layer 11 are aligned in a direction intersecting the stacking direction of the first layer 13 and the second layer 11, as shown in Figure 20, or by a configuration in which the second layer bias magnetic field source, consisting of permanent magnets 70 or electromagnets, and the second layer 11 are aligned in the stacking direction of the first layer 13 and the second layer 11, as shown in Figure 23. Furthermore, the inverse magnetostrictive effect of the anisotropic variable layer 22 also makes it possible to orient the magnetization 11m towards Z1. However, since the length (thickness) of the anisotropic variable layer 22 in the Z1-Z2 direction is significantly shorter than the length in other directions, it is difficult to use shape magnetic anisotropy as a second layer bias magnetic field source, as shown in Figures 21 and 22.

[0120] The present invention is useful as a magnetic sensor and magnetic measurement method with high magnetic resolution that can detect external magnetic fields with high sensitivity.

[0121] 1: Magnetic sensor 2, 2A: 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: Magnetoresistive element 11: Second layer 12: Non-magnetic layer 13: First layer 15: Full bridge circuit 16: Half bridge circuit 20: Magnetization control unit 21: Spin Hall layer 22: Anisotropic variable layer 61: Control wiring 62: Measurement wiring 70: Permanent magnet layer 71, 72: Permanent magnet 100a, 100b, 100c, 100d: Variable magnetic field detection unit 101: First variable magnetic field detection unit 102: Second variable magnetic field detection unit 111: Variable second layer 112 : Variable current supply second layer 20c : Control current 11m, 13m, 20m, 22m, 70m, 71m, 72m, 111m, 112m, 222m : Magnetization 21af, 22af : Exchange coupling 20s1, 20s2 : Spin current 201 : Electromagnetic control unit 221 : Antiferromagnetic layer 222 : Magnetic layer GND : Ground terminal H, H', H'' : Measurement magnetic field I : Control current source V : Measurement voltage source V1, V2 : Output terminal VA : Output section Vdd : Power supply terminal

Claims

1. A magnetic sensor characterized by comprising a magnetoresistive element having a first layer that can be magnetized in a direction along the measuring magnetic field, a second layer that can maintain magnetization in a predetermined direction even when subjected to the measuring magnetic field, and a non-magnetic layer located between the first layer and the second layer, and a variable magnetic field detection unit having a magnetization control unit that changes the direction of magnetization of the second layer.

2. The magnetic sensor according to claim 1, wherein the magnetization control unit forms a laminated structure with the magnetoresistive element.

3. The magnetic sensor according to claim 1, wherein the second layer is reversibly switchable between a first state in which the magnetization is maintained in a first direction even when subjected to the measurement magnetic field, and a second state in which the magnetization is maintained in a second direction different from the first direction even when subjected to the measurement magnetic field, and the magnetization control unit is energized when the second layer is in the second state.

4. The magnetic sensor according to claim 3, wherein the magnetization control unit is in a non-energized state when the second layer is in the first state.

5. The magnetic sensor according to claim 3, wherein when the second layer is in the first state, the magnetization control unit is in a different energized state than when the second layer is in the first state.

6. The magnetic sensor according to claim 1, wherein the magnetization control unit has a spin Hall layer made of a layered body that generates a spin-orbit torque when energized, and the direction of the magnetization of the second layer is reversibly changed based on the spin-orbit torque from the spin Hall layer.

7. The magnetic sensor according to claim 6, wherein the spin Hall layer has a portion made of a non-magnetic material.

8. The magnetic sensor according to claim 6 or 7, wherein the spin Hall layer has a portion made of an antiferromagnetic material.

9. The magnetic sensor according to claim 6, wherein the magnetization control unit forms a laminated structure with the magnetoresistive element, and the magnetization control unit comprises a layered body located between the spin Hall layer and the second layer, and has an anisotropic variable layer that is magnetically coupled to the second layer and has magnetic anisotropy, and the anisotropic variable layer receives the spin orbit torque from the spin Hall layer and the direction of magnetization is reversibly changed.

10. The magnetic sensor according to claim 9, wherein the anisotropic variable layer has a portion made of a ferromagnetic material.

11. The magnetic sensor according to claim 9 or 10, wherein the anisotropic variable layer has a portion made of an antiferromagnetic material.

12. The magnetic sensor according to claim 9, further comprising a bias magnetic field source that aligns the magnetization of at least a portion of the anisotropic variable layer to a predetermined direction when the magnetization control unit is in an unenergized state.

13. The magnetic sensor according to claim 12, wherein the bias magnetic field source is based on exchange coupling between an antiferromagnetic material and a magnetic material.

14. The magnetic sensor according to claim 13, wherein the spin Hall layer is made of an antiferromagnetic material and has a portion that constitutes the bias magnetic field source.

15. The magnetic sensor according to claim 14, wherein the spin Hall layer has a portion made of a non-magnetic material.

16. The magnetic sensor according to claim 13, wherein the anisotropic variable layer is made of an antiferromagnetic material and has a portion that constitutes the bias magnetic field source.

17. The magnetic sensor according to claim 12, wherein the anisotropic variable layer has at least one of shape magnetic anisotropy and crystal magnetic anisotropy as the bias magnetic field source.

18. The magnetic sensor according to claim 1, wherein the magnetization control unit is an electromagnetically controlled magnetization control unit capable of reversibly changing the direction of magnetization by energizing, and the electromagnetically controlled magnetization control unit is magnetically coupled to the second layer.

19. The magnetic sensor according to claim 18, wherein the electromagnetic control unit has a portion made of an antiferromagnetic material.

20. The magnetic sensor according to claim 18, wherein the electromagnetic control unit has a portion that generates the spin Hall effect.

21. The magnetic sensor according to claim 6, wherein the second layer is a variable second layer whose magnetization direction is changed by receiving the spin orbit torque from the spin Hall layer.

22. The magnetic sensor according to claim 21, wherein the variable second layer has a portion made of a ferromagnetic material.

23. The magnetic sensor according to claim 21, wherein the variable second layer has a portion made of an antiferromagnetic material.

24. A magnetic sensor comprising a variable magnetic field detection unit having a magnetoresistive element having a first layer that can be magnetized in a direction along the measuring magnetic field, a second layer that can maintain a state in which the magnetization is aligned in a first direction even when subjected to the measuring magnetic field, and a non-magnetic layer located between the first layer and the second layer, wherein the second layer is reversibly switchable between a first state in which the magnetization is maintained in a first direction even when subjected to the measuring magnetic field, and a second state in which the magnetization is maintained in a second direction different from the first direction even when subjected to the measuring magnetic field.

25. The magnetic sensor according to claim 24, wherein the second layer is a variable energizing second layer that enters the second state when the second layer is energized.

26. The magnetic sensor according to claim 25, wherein the variable current-carrying second layer has a portion made of an antiferromagnetic material.

27. The magnetic sensor according to claim 25, wherein the variable current-carrying second layer has a portion that generates the spin Hall effect.

28. The magnetic sensor according to claim 25, wherein when the variable energization second layer is in the first state, the variable energization second layer is in a non-energized state.

29. The magnetic sensor according to claim 25, wherein when the variable-energy second layer is in the first state, the variable-energy second layer is in a different energized state than when the variable-energy second layer is in the first state.

30. The magnetic sensor according to claim 3 or claim 24, wherein the first orientation and the second orientation are in the same direction but opposite directions.

31. The magnetic sensor according to claim 30, 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 magnetization of the second layer is in the first direction, and a second output from the variable magnetic field detection unit when the magnetization of the second layer is in the second direction.

32. A magnetic sensor according to claim 30, comprising a magnetic field detection unit having a half-bridge circuit including two of the variable magnetic field detection units, wherein the magnetic field detection unit is capable of outputting a first signal output from the half-bridge circuit when the second layer of one of the two of the variable magnetic field detection units is in the first state, and a second signal output from the half-bridge circuit when the second layer of one of the two of the variable magnetic field detection units is in the second state, and comprising a magnetic field calculation unit that calculates the measured magnetic field based on the first signal and the second signal.

33. A magnetic sensor according to claim 30, comprising a magnetic field detection unit having a full bridge circuit including four of the variable magnetic field detection units, wherein the magnetic field detection unit is capable of outputting a first signal output from the full bridge circuit when the second layer of two of the four variable magnetic field detection units is in the first state, and a second signal output from the full bridge circuit when the magnetization of the second layer of the four variable magnetic field detection units is in the opposite direction to when the first signal is output, and comprising a magnetic field calculation unit that calculates the measured magnetic field based on the first signal and the second signal.

34. The magnetic sensor according to claim 30, wherein the variable magnetic field detection unit is reversibly switchable between a first state and a second state and comprises a first variable magnetic field detection unit and a second variable magnetic field detection unit connected in series, and an output unit that outputs an electrical signal relating to the potential between the first variable magnetic field detection unit and the second variable magnetic field detection unit connected in series, wherein the first variable magnetic field detection unit and the second variable magnetic field detection unit are controlled so that their respective second layers are magnetized in opposite directions, and further comprises a magnetic field calculation unit that performs calculation processing using the electrical signal from the output unit as input and calculates the measured magnetic field, wherein the calculation processing includes determining the difference between a first electrical signal output from the output unit when the magnetization of the second layer of the first variable magnetic field detection unit is in a first direction and a second electrical signal output from the output unit when the magnetization of the second layer of the first variable magnetic field detection unit is in a second direction.

35. The magnetic sensor according to claim 3 or claim 24, wherein the first orientation and the second orientation are aligned in different directions from each other.

36. The magnetic sensor according to claim 35, wherein the first orientation is along a first orthogonal direction which is one of the directions perpendicular to the stacking direction in which the first layer and the second layer are aligned, and the second orientation is along a second orthogonal direction which is perpendicular to the stacking direction and intersects the first orthogonal direction.

37. The magnetic sensor according to claim 36, wherein the first orthogonal direction and the second orthogonal direction are orthogonal.

38. The magnetic sensor according to claim 35, wherein the first orientation is along a first orthogonal direction which is one of the directions perpendicular to the stacking direction in which the first layer and the second layer are aligned, and the second orientation is along the stacking direction.

39. The magnetic sensor according to claim 35, wherein the first orientation is along the stacking direction in which the first layer and the second layer are aligned, and the second orientation is along a first orthogonal direction which is one of the directions perpendicular to the stacking direction.

40. The magnetic sensor according to claim 35, wherein the measured magnetic field has a component along the first direction and a component along the second direction.

41. The magnetic sensor according to claim 35, further comprising a magnetic field calculation unit that calculates the strength of the measured magnetic field based on a first output from the variable magnetic field detection unit when the second layer is in the first state and a second output from the variable magnetic field detection unit when the second layer is in the second state.

42. The magnetic sensor according to claim 35, further comprising a magnetic field calculation unit that calculates the direction of the measured magnetic field based on a first output from the variable magnetic field detection unit when the second layer is in the first state and a second output from the variable magnetic field detection unit when the second layer is in the second state.

43. The magnetic sensor according to claim 4, further comprising a second layer bias magnetic field source that applies a magnetic field to the second layer to maintain the magnetization of the second layer in a first orientation in the first state.

44. The magnetic sensor according to claim 43, wherein the magnetization control unit has an antiferromagnetic section made of an antiferromagnetic material, and the exchange coupling based on the antiferromagnetic section becomes the second layer bias magnetic field source.

45. The magnetic sensor according to claim 28, further comprising a second layer bias magnetic field source that applies a magnetic field to the second layer to maintain the magnetization of the second layer in a first direction in the first state.

46. ​​The magnetic sensor according to claim 45, wherein the variable current-carrying second layer has a junction between an antiferromagnetic material and a ferromagnetic material, and the exchange coupling generated at the junction becomes the bias magnetic field source for the second layer.

47. The magnetic sensor according to claim 43 or 45, wherein the second layer bias magnetic field source includes at least one of a coil that generates an induced magnetic field by energizing and a permanent magnet.

48. The magnetic sensor according to claim 43 or claim 45, wherein the second layer bias magnetic field source and the second layer are aligned in the stacking direction in which the first layer and the second layer are aligned.

49. The magnetic sensor according to claim 43 or claim 45, wherein the second layer bias magnetic field source and the second layer are arranged in a direction that intersects the stacking direction in which the first layer and the second layer are aligned.

50. The magnetic sensor according to claim 4 or claim 28, wherein in the first state, the magnetization of the second layer is maintained in the first orientation based on shape magnetic anisotropy and / or crystal magnetic anisotropy.

51. A magnetic measurement method using a magnetic sensor comprising: a magnetoresistive element having a first layer that can be magnetized in a direction along the measuring magnetic field, a second layer that can maintain magnetization in a predetermined direction even when subjected to the measuring magnetic field, and a non-magnetic layer located between the first layer and the second layer; a variable magnetic field detection unit having a magnetization control unit that changes the direction of the magnetization of the second layer; a magnetic field calculation unit that calculates the measuring magnetic field based on a first output from the variable magnetic field detection unit in a first state in which the magnetization of the second layer is maintained in a first direction even when subjected to the measuring magnetic field, and a second output from the variable magnetic field detection unit in a second state in which the magnetization of the second layer is maintained in a second direction different from the first direction even when subjected to the measuring magnetic field, wherein the second layer can be reversibly switched between the first state and the second state, the method comprising: a first step of causing the variable magnetic field detection unit to output the first output; a second step of causing the variable magnetic field detection unit to output the second output; A magnetic measurement method characterized by comprising: a third step in which the magnetic field calculation unit calculates the measurement magnetic field based on the first output and the second output.

52. A magnetic measurement method using a magnetic sensor comprising: a variable magnetic field detection unit having a magnetoresistive element having a first layer that can be magnetized in a direction along the measuring magnetic field, a second layer that can maintain magnetization in a predetermined direction even when subjected to the measuring magnetic field, and a non-magnetic layer located between the first layer and the second layer; a magnetic field calculation unit that calculates the measuring magnetic field based on a first output from the variable magnetic field detection unit in a first state in which the magnetization of the second layer is maintained in a first direction even when subjected to the measuring magnetic field, and a second output from the variable magnetic field detection unit in a second state in which the magnetization of the second layer is maintained in a second direction different from the first direction even when subjected to the measuring magnetic field, wherein the second layer is reversibly switchable between the first state and the second state, and is an energized variable second layer that enters the second state when the second layer is energized, the method comprising: a first step of causing the variable magnetic field detection unit to output the first output; a second step of causing the variable magnetic field detection unit to output the second output; A magnetic measurement method characterized by comprising: a third step in which the magnetic field calculation unit calculates the measurement magnetic field based on the first output and the second output.

53. The magnetic measurement method according to claim 51 or claim 52, wherein the first direction and the second direction are opposite directions in the same direction, and the direction of the measurement magnetic field is calculated based on the first output and the second output.

54. The magnetic measurement method according to claim 51 or claim 52, wherein the first orientation and the second orientation are in different directions from each other, and the orientation of the measurement magnetic field is calculated based on the first output and the second output.

55. A magnetic field detection unit having a half-bridge circuit including two variable magnetic field detection units, wherein the magnetic field detection unit outputs a first signal when one of the two variable magnetic field detection units of the half-bridge circuit is in a first state and outputs a second signal when it is in a second state, and the magnetic field measurement method according to claim 53, comprising: an I step of causing the magnetic field detection unit to output the first signal instead of the first to third steps; a II step of causing the magnetic field detection unit to output the second signal; and a III step of calculating the measured magnetic field in the magnetic field calculation unit based on the first signal and the second signal.

56. A magnetic field detection unit having a full bridge circuit including four variable magnetic field detection units, wherein the magnetic field detection unit outputs a first signal when the magnetization of the second layer of two of the four variable magnetic field detection units of the full bridge circuit is in the first state and the magnetization of the second layer of the other two is in the second state, and outputs a second signal when the magnetization of the second layer of the four variable magnetic field detection units of the full bridge circuit is in the opposite direction to when the first signal is output, and the magnetic field measurement method according to claim 53, comprising: an I step of causing the magnetic field detection unit to output a first signal instead of the first to third steps; a II step of causing the magnetic field detection unit to output a second signal; and a III step of calculating the measured magnetic field in the magnetic field calculation unit based on the first signal and the second signal.

57. The variable magnetic field detection unit is reversibly switchable between the first state and the second state and comprises a first variable magnetic field detection unit and a second variable magnetic field detection unit connected in series, and an output unit that outputs an electrical signal relating to the potential between the first variable magnetic field detection unit and the second variable magnetic field detection unit connected in series, wherein the first variable magnetic field detection unit and the second variable magnetic field detection unit are controlled so that their respective second layers are magnetized in opposite directions, the magnetic field calculation unit performs calculation processing using the electrical signals from the output unit as input instead of the first and second outputs, in the first step, the variable magnetic field detection unit outputs a first electrical signal that is output from the output unit when the magnetization of the second layer of the first variable magnetic field detection unit is in the first direction instead of the first output, in the second step, the variable magnetic field detection unit outputs a second electrical signal that is output from the output unit when the magnetization of the second layer of the first variable magnetic field detection unit is in the second direction instead of the second output, The magnetic measurement method according to claim 53, wherein in the third step, the measurement magnetic field is calculated based on the first electrical signal and the second electrical signal instead of the first output and the second output.

58. The magnetic measurement method according to claim 57, wherein the third step includes calculating the measurement magnetic field by determining the difference between the first electrical signal and the second electrical signal.

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