Magnetic sensor and magnetic measurement method

Abstract

To provide a magnetic sensor that makes it possible to measure a small magnetic field with high sensitivity, and that can contribute to downsizing.SOLUTION: Provided is a magnetic sensor 1 characterized by comprising a variable magnetic field detection part 100a including: a magnetoresistance effect element 10a having a first layer 13 which can be magnetized in a direction along a measurement magnetic field, a second layer 11 capable of maintaining the magnetization direction in a first direction (X direction), and a non-magnetic layer 12 located between the first layer 13 and the second layer 11; and a magnetization control part 20 for reversibly reversing the direction of magnetization 11 m of the second layer 11. The magnetization control part 20 can be an energizing magnetization control part 201 with which the magnetization direction is reversed by energization, and can have a spin torque generation part 21 and an anisotropy variable part 22. The magnetization control part 20 can have the spin torque generation part 21, in which the second layer 11 can be a variable second layer 111, or the second layer 11 can be integrated with the magnetization control part 20 to form an energizing variable second layer 112.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a magnetic sensor including a magnetoresistive element. [Background technology]

[0002] Some magnetic sensors that detect and measure magnetic fields include those equipped with magnetoresistive elements that utilize the GMR (giant magnetoresistance) effect or the TMR (tunneling magnetoresistance) effect. The magnetoresistive elements in these magnetic sensors are configured with a fixed magnetic layer, a non-magnetic intermediate layer, and a free magnetic layer stacked in this order. When an external magnetic field to be measured is applied to the magnetoresistive element, the magnetization direction of the free magnetic layer changes, causing a resistance change according to the angle between the magnetization direction of the free magnetic layer and the magnetization direction of the fixed magnetic layer. A magnetic sensor equipped with a magnetoresistive element can detect a magnetic field using the resistance change of the magnetoresistive element.

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

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

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

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

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

[0008] [Patent Document 1] Japanese Patent Application Publication No. 2018-115972 [Patent Document 2] Japanese Patent Publication No. 2020-148727 [Patent Document 3] Special Publication No. 2012-518788 [Patent Document 4] Special Publication No. 2009-544004 Summary of the Invention [Problem to be solved by the invention]

[0009] There is a strong demand for improving the resolution (magnetic resolution) of magnetic sensors equipped with magnetoresistive effect 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 effect element that has a configuration different from conventional ones and is capable of measuring small magnetic fields with high accuracy. [Means for solving the problem]

[0010] In one aspect, the present invention provides a magnetic sensor characterized by comprising a magnetoresistive element having a first layer that can be magnetized in a direction along the measurement magnetic field, a second layer that can maintain its magnetization along a first direction, 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 reversibly reverses the magnetization of the second layer.

[0011] In conventional magnetoresistive elements, when measuring an external magnetic field to be measured, one of the two magnetic layers becomes a magnetization fixed layer and the direction of magnetization is fixed, but in a magnetic sensor according to one aspect of the present invention, the external magnetic field is measured in two states: a state (first state) in which the magnetization of the second layer corresponding to this magnetization fixed layer is fixed in one direction, and a state (second state) in which the magnetization of the second layer is fixed in the opposite direction (anti-parallel) to the first state. High-precision measurement is possible by taking the difference between the electrical signals containing the measurement results in each state.

[0012] The above magnetic sensor may further include a magnetic field calculation unit that calculates the measured magnetic field based on a first output from the variable magnetic field detection unit when the magnetization of the second layer is in one direction of the first direction and a second output from the variable magnetic field detection unit when the magnetization of the second layer is in the other direction of the first direction.

[0013] When there is a correlation between the noise contained in the electrical signal based on the first output and the noise contained in the electrical signal based on the second output, the noise signal, particularly 1 / f noise, can be removed by taking the difference between these electrical signals.

[0014] In the above magnetic sensor, the variable magnetic field detection unit includes a first variable magnetic field detection unit and a second variable magnetic field detection unit that are connected in series and each have the magnetoresistive element and the magnetization control unit, and are controlled so that the second layers are magnetized in opposite directions to each other, and an output unit that outputs an electrical signal related to the potential between the first variable magnetic field detection unit and the second variable magnetic field detection unit that are connected in series, and 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 to each other, and further includes a magnetic field calculation unit that performs arithmetic processing using the electrical signal from the output unit as input and calculates the measured magnetic field, and the arithmetic processing may include calculating 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 one direction of 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 other direction of the first direction.

[0015] Measurement using a full-bridge circuit, which is one method for achieving high-precision measurements, requires four magnetoresistive effect elements in one magnetic sensor. To achieve high-precision measurements, it is necessary for these four magnetoresistive effect elements to have characteristics as similar as possible. The magnetization of the second layer of the magnetoresistive effect element of the magnetic sensor according to the present invention can be reversed by a magnetization control unit. This allows a half-bridge circuit, in which two magnetoresistive effect elements are connected in series, to output two types of electrical signals related to the midpoint potential output from the full-bridge circuit, thereby enabling the magnetic sensor to be miniaturized. Furthermore, because two types of electrical signals can be obtained with fewer magnetoresistive effect elements than in a full-bridge circuit, the uniformity of the magnetoresistive effect elements is higher than in a full-bridge circuit, and higher measurement accuracy is expected.

[0016] In the above magnetic sensor, the magnetization control unit may have a spin torque generation unit that generates a spin orbit torque when current is applied, and the magnetization of the second layer may be reversibly reversed based on the spin orbit torque from the spin torque generation unit.

[0017] In the case where the magnetization control unit has the above-mentioned spin torque generation unit, the magnetization control unit has an anisotropy variable unit that can reversibly reverse magnetization based on the spin orbit torque from the spin torque generation unit, and the anisotropy variable unit may be magnetically coupled to the second layer, and further, the anisotropy variable unit may have a portion made of an antiferromagnetic material.

[0018] In the case where the above-mentioned spin torque generation unit is included, the second layer may be a variable second layer having a portion whose magnetization can be reversibly reversed based on the spin-orbit torque from the spin torque generation unit, and the variable second layer may have a portion made of an antiferromagnetic material.

[0019] In the magnetic sensor, the second layer may be a variable current second layer that is integrated with the magnetization control section and has a portion made of an antiferromagnetic material whose magnetization can be reversibly reversed when current is applied.

[0020] In the magnetic sensor, the magnetization control section may be an electromagnetization control section capable of reversibly inverting magnetization by energization. [Effects of the Invention]

[0021] According to the present invention, a magnetic sensor with high magnetic resolution is provided, and the present invention also contributes to further miniaturization of the magnetic sensor. [Brief explanation of the drawings]

[0022] [Figure 1] 1 is a block diagram of a magnetic sensor according to an embodiment of the present invention; [Figure 2] 3 is an explanatory diagram of a magnetic field detection unit included in the magnetic sensor according to the embodiment of the present invention. FIG. [Figure 3] 3A and 3B are diagrams illustrating an example of a variable magnetic field detection unit included in the magnetic sensor according to the first embodiment of the present invention. [Figure 4] 3A and 3B are diagrams illustrating a first state of an example of a variable magnetic field detection unit of the magnetic sensor according to the first embodiment of the present invention. [Figure 5]5A and 5B are diagrams illustrating a second state of an example of a variable magnetic field detection unit of the magnetic sensor according to the first embodiment of the present invention. [Figure 6] 4 is a flowchart illustrating a first measurement method using the magnetic sensor according to the first embodiment of the present invention. [Figure 7] 3 is an explanatory diagram of a magnetic field detection unit included in the magnetic sensor according to the embodiment of the present invention. FIG. [Figure 8] 5A and 5B are diagrams illustrating another example of the variable magnetic field detection unit included in the magnetic sensor according to the first embodiment of the present invention. [Figure 9] 5A and 5B are diagrams illustrating 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. [Figure 10] 10A and 10B are diagrams illustrating 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. [Figure 11] 5A to 5C are diagrams illustrating modified examples of the variable magnetic field detection unit included in the magnetic sensor according to the first embodiment of the present invention. [Figure 12] 10A and 10B are diagrams illustrating an example of a variable magnetic field detection unit included in a magnetic sensor according to a second embodiment of the present invention. [Figure 13] 10A and 10B are diagrams illustrating an example of a variable magnetic field detection unit included in a magnetic sensor according to a third embodiment of the present invention. [Figure 14] 5A and 5B are diagrams illustrating a second measurement method (first state) using the magnetic sensor according to the first embodiment of the present invention. [Figure 15] 5A and 5B are diagrams illustrating a second measurement method (second state) using the magnetic sensor according to the first embodiment of the present invention. [Figure 16] 2A to 2C are diagrams illustrating in detail an example of a variable magnetic field detection unit included in the magnetic sensor according to the first embodiment of the present invention. [Figure 17] 6 is a flowchart illustrating the first measurement method using the magnetic sensor according to the first embodiment of the present invention from another perspective. [Figure 18] 5A and 5B are diagrams illustrating in detail an example (modification) of a variable magnetic field detection unit included in the magnetic sensor according to the first embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0023] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In each drawing, the same components are designated by the same reference numerals, and their description will be omitted. Reference coordinates are indicated in each drawing as appropriate to indicate the positional relationship of each component.

[0024] Fig. 1 is a block diagram of a magnetic sensor according to one embodiment of the present invention. Fig. 2 is an explanatory diagram of a magnetic field detection unit provided in the magnetic sensor according to one embodiment of the present invention. The magnetic sensor 1 of this embodiment includes a magnetic field detection unit 2, a control power supply 3, a magnetic field calculation unit 4, an amplifier 5, an analog-to-digital conversion circuit (A / D conversion circuit 6), and a control unit 7. The control unit 7 controls the various units that make up the magnetic sensor 1, and is configured as a CPU (central processing unit), a program, etc.

[0025] The magnetic field detection unit 2 detects an external magnetic field (measurement magnetic field H) to be measured. As shown in FIG. 2, the magnetic field detection unit 2 is configured with a full bridge circuit 15 having magnetoresistive effect elements 10a, 10b, 10c, and 10d that measure a magnetic field along the X direction. In this embodiment, the magnetic field detection unit 2 has variable magnetic field detection units 100a, 100b, 100c, and 100d corresponding to the magnetoresistive effect elements 10a, 10b, 10c, and 10d, respectively. The control power supply 3 applies a predetermined current or a predetermined voltage to each unit based on a control signal from the control unit 7.

[0026] 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 configured, for example, with 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 a first state and the two variable magnetic field detection units 100a and 100d are in a 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 a signal based on the first signal and a signal based on the second signal, a measured signal from which 1 / f noise has been removed can be obtained. The first state and the second state will be described in detail later.

[0027] In the magnetic sensor 1, the magnetic field calculation unit 4 calculates the measured magnetic field H, and then 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.

[0028] 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 one embodiment of the present invention may be provided on the same substrate (one chip). In this embodiment, the four magnetoresistive effect elements 10a, 10b, 10c, and 10d are provided on the same substrate (not shown), and FIG. 2 is a view of the magnetic field detection unit 2 of the magnetic sensor 1 as viewed from the stacking surface (front surface) of the substrate in the normal direction of the substrate. That is, in FIG. 2, the Z1 side is the front surface of the substrate, and the Z2 side is the back surface of the substrate. The Z direction is along the stacking direction of the magnetoresistive effect elements 10a, 10b, 10c, and 10d.

[0029] The magnetic field detection unit 2 has a full bridge circuit 15 in which a first half bridge circuit, in which a magnetoresistance effect element 10a and a magnetoresistance effect element 10b, both of which extend in the Y direction, are connected in series, and a second half bridge circuit, in which a magnetoresistance effect element 10c and a magnetoresistance effect element 10d, both of which extend in the Y direction, are connected in series, are connected in parallel between a power supply terminal Vdd, which is a power supply feeding point, and a ground terminal GND.

[0030] The first half-bridge circuit has an output terminal V1 between the magnetoresistive element 10a and the magnetoresistive element 10b. The second half-bridge circuit has an output terminal V2 between the magnetoresistive element 10c and the magnetoresistive element 10d. The magnitude of the external magnetic field applied from the outside as the measurement magnetic field H can be quantitatively measured based on the potential difference between the outputs from these two output terminals V1 and V2 (midpoint potential Va of the first half-bridge circuit - midpoint potential Vb of the second half-bridge circuit). In this embodiment, the magnetic field detection unit 2 outputs a signal including the midpoint potential Va from the output terminal V1 and a signal including the midpoint potential Vb from the output terminal V2. The processing performed by the magnetic field calculation unit 4 includes calculating the midpoint potential difference using these signals as inputs.

[0031] In a pair of magnetoresistive elements 10a and 10b forming a first half-bridge circuit, a second layer 11 (see FIG. 3), which corresponds to the "pinned magnetic layer" of a magnetoresistive element according to the prior art, can maintain 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 oriented in the X2 direction (magnetoresistive element 10a) and the X1 direction (magnetoresistive element 10b), as indicated by the white arrows in FIG. 2. In addition, in a pair of magnetoresistive elements 10c and 10d forming a second half-bridge circuit, the magnetization 11m of the second layer 11 is oriented in the X1 direction (magnetoresistive element 10c) and the X2 direction (magnetoresistive element 10d), as indicated by the white arrows in FIG. 2.

[0032] In the first half-bridge circuit and the second half-bridge circuit, the magnetization 11m of the second layer 11 of the magnetoresistive effect element 10b on the power supply terminal Vdd side and the magnetoresistive effect element 10d is opposite (anti-parallel). The magnetization 11m of the second layer 11 of the magnetoresistive effect element 10a on the ground terminal GND side and the magnetoresistive effect element 10c is opposite (anti-parallel). Therefore, the sensitivity axis direction of the magnetoresistive effect 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."

[0033] 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 FIG. 3), which corresponds to the "free magnetic layer" of the conventional magnetoresistive element, is oriented in the same direction, along the Y direction Y2 (hereinafter abbreviated as "Y2 direction"; the same applies to other directions), as indicated by the black arrow in FIG. 2. When the first layer 13 is subjected to the measurement magnetic field H in the first direction (X direction), it can be magnetized in the direction along the measurement magnetic field H. There are no particular limitations on the method for aligning the magnetization 13m of the first layer 13 when no measurement magnetic field H is applied. An external bias magnetic field or induced magnetic field may be applied, or exchange coupling with an antiferromagnetic layer that interacts with the first layer 13 may be used.

[0034] With the above-described configuration, the output terminal V1 from the first half-bridge circuit and the output terminal V2 from the second half-bridge circuit change in opposite directions as the magnitude of the measured magnetic field H in the X direction changes. Therefore, a large output is obtained as the potential difference (Va-Vb) between the two output terminals V1 and V2. Therefore, the magnetic sensor 1 can detect the measured magnetic field H with high accuracy. Note that the full-bridge circuit 15 can be replaced by a first half-bridge circuit or a second half-bridge circuit, or the magnetoresistive effect element 10a can be used alone.

[0035] 2, the magnetic sensor 1 according to this embodiment includes variable magnetic field detection units 100a, 100b, 100c, and 100d that correspond to the magnetoresistive elements 10a, 10b, 10c, and 10d, respectively, and measure the measurement magnetic field H by reversing the magnetization 11m of the second layer 11. Hereinafter, the variable magnetic field detection unit 100a will be described as a specific example.

[0036] (First embodiment) Fig. 3 is a diagram illustrating an example of a variable magnetic field detection unit included in the magnetic sensor according to the first embodiment of the present invention. Fig. 4 is a diagram illustrating a first state of the example of the variable magnetic field detection unit of the magnetic sensor according to the first embodiment of the present invention. Fig. 5 is a diagram illustrating a second state of the example of the variable magnetic field detection unit of the magnetic sensor according to the first embodiment of the present invention.

[0037] The variable magnetic field detection unit 100a has a magnetoresistive effect element 10a that exhibits a magnetoresistive effect and includes a first layer 13 that can be magnetized in a direction along the measurement 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.

[0038] The components of the magnetoresistive element 10a are stacked in the second direction (Z direction), and as described above, the first layer 13 corresponds to the "free magnetic layer" in a magnetoresistive element according to the prior art, and the second layer 11 corresponds to the "pinned magnetic layer" in a magnetoresistive element according to the prior art. By detecting the resistance value caused by the misalignment of the magnetization directions of these layers sandwiching the nonmagnetic layer 12, the strength of the measurement magnetic field H applied to the first layer 13 can be measured.

[0039] The second layer 11 of the magnetoresistive effect element 10a provided in the variable magnetic field detection unit 100a of the magnetic sensor 1 of this embodiment is different from the ``fixed magnetic layer'' of the magnetoresistive effect element of the conventional technology in that the magnetization 11m of the second layer 11 maintains a state along a predetermined orientation in the first direction even when subjected to a measurement magnetic field H within the measurement range of the magnetoresistive effect element 10a, but can be reversed by the magnetization control unit 20.

[0040] The second layer 11 is made of a magnetic material such as a CoFe alloy (cobalt-iron alloy). When the magnetoresistive element 10a is a tunneling magnetoresistive element (TMR), the non-magnetic layer 12 is an insulating barrier layer made of, for example, MgO, Al2O3, or titanium oxide. The first layer 13 is made of a soft magnetic material such as a CoFe alloy or a NiFe alloy (nickel-iron alloy). The second layer 11 and the first layer 13 may have a single-layer structure or a multilayer structure. In the case of a multilayer structure, a synthetic ferrimagnetic structure may be preferable. When the magnetoresistive element 10a is a giant magnetoresistive element (GMR), the non-magnetic layer 12 is made of a non-magnetic material such as Cu. In this embodiment, the first layer 13 is located on the Z1 side of the magnetoresistive element 10a, and the sensing center 10P of the magnetoresistive element 10a is located at the center of the first layer 13.

[0041] The magnetoresistive element 10a of the variable magnetic field detection unit 100a according to this embodiment is formed of a tunneling magnetoresistive element (TMR) as a specific example, and measurement wiring 62 is provided so that a voltage from a measurement voltage source V is applied in the second direction (Z direction) between the first layer 13 and the second layer 11 of the magnetoresistive element 10a in order to measure the electrical characteristics of the magnetoresistive element 10a. Note that 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, so the measurement wiring 62 is provided so that the voltage from the measurement voltage source V is applied to the first layer 13 via the magnetization control unit 20.

[0042] In the variable magnetic field detecting unit 100 a according to this embodiment, the magnetization control unit 20 includes a spin torque generating unit 21 and an anisotropy variable unit 22 .

[0043] The spin torque generator 21 generates a spin orbit torque when current is applied, and the magnetization 11m of the second layer 11 is reversed based on the spin orbit torque from the spin torque generator 21. In this embodiment, the spin orbit torque generated in the spin torque generator 21 affects the anisotropy variable unit 22, and the magnetization 20m of the anisotropy variable unit 22 is aligned in a predetermined direction. Since the anisotropy variable unit 22 is magnetically connected to the second layer 11, the second layer 11 is magnetized so as to align with the magnetization 20m of the anisotropy variable unit 22.

[0044] When a current is applied to the spin torque generation unit 21 in the XY in-plane direction, the spin Hall effect, the Rashba-Edelstein effect, etc. are generated, and a spin orbit torque is applied to the anisotropy variable unit 22. Materials constituting the spin torque generation unit 21 include heavy metals (5d transition metals) such as Hf, Ta, W, Pt, and Ir, which have high specific gravity among paramagnetic transition metals; topological insulators such as BiSb, BiSe, Bi2Se3, and Bi2Te3; Mn3X (X = Sn, Ge, Ga, RH, Pt, Ir), Mn 1-x Tr x Examples include antiferromagnetic materials such as gamma-phase (Tr = Ni, Fe, Cu, Ru, Pd, Ir, RH, Pd, Pt); half-Heusler alloy topological semimetals such as LuPtSb, LuPdBi, LuPtBi, ScPtBi, YAuPb, LaPtBi, CePtBi, THPtPb, and LaAuPb, as well as mixed crystals of these.

[0045] In the specific example shown in FIG. 3, the spin torque generation unit 21 is a film-like body, and this film-like body may be composed of a single structure, i.e., a single-layer film, or may be composed of a laminated film. In the case of a laminated film, a boundary region may be formed between adjacent films. The spin torque generation unit 21 may be composed entirely of a single material, or may be composed of multiple materials. When composed of multiple materials, it may have a laminated structure as described above, or it may have a dispersed structure. In the case of a dispersed structure, the degree of dispersion is arbitrary, and it may be a structure in which nanocrystals are dispersed, or a fixed pattern may be formed. In addition, a compositional distribution may be set in the spin torque generation unit 21.

[0046] The anisotropy variable unit 22 is capable of reversibly reversing its magnetization 20m based on the spin orbit torque from the spin torque generator 21. Furthermore, since the anisotropy variable unit 22 is magnetically coupled to the second layer 11 of the magnetoresistive element 10a, the magnetization 11m of the second layer 11 is reversed based on the spin orbit torque from the spin torque generator 21. Like the spin torque generator 21, the anisotropy variable unit 22 may be made of a single material or a plurality of materials. When made of a plurality of materials, the anisotropy variable unit 22 may have a dispersed structure, or a compositional distribution may be set.

[0047] The anisotropy variable part 22 may be made of any material as long as it performs this magnetization reversal function. Like the second layer 11, it may be made of a ferromagnetic material, or it may be made of an antiferromagnetic material. Specific examples of antiferromagnetic materials include at least some of the materials that make up the spin torque generation part 21. When the anisotropy variable part 22 includes an antiferromagnetic material, a magnetic field (e.g., a virtual magnetic field) may be generated inside the anisotropy variable part 22 based on a physical phenomenon different from the magnetization when the anisotropy variable part 22 includes a ferromagnetic material. Therefore, in this specification, the concept of the term "magnetization" related to the anisotropy variable part 22, etc., also includes the generation of a magnetic field inside the anisotropy variable part 22 based on a physical phenomenon different from the magnetization of such a ferromagnetic material.

[0048] (First state) 4 is a state in which a first output is output from the variable magnetic field detection unit 100a. In this example, the control wiring 61 is provided so that a current (control current 20c) from the control current source I is applied to the spin torque generation unit 21 in the X1-X2 direction.

[0049] In the first state, the control current 20c of the spin torque generator 21 is oriented in the X2 direction, and the magnetization 11m of the second layer 11 is oriented in the X1 direction. The current flowing through the spin torque generator 21 generates a spin current 20s1 in the Z direction in the spin torque generator 21, and spins oriented in a predetermined direction are injected into the anisotropy variable unit 22 from the Z direction Z1 side of the spin torque generator 21. The magnetization 20m of the anisotropy variable unit 22 is oriented in the X1 direction due to the spin orbit torque based on this injected spin. From the viewpoint of improving the controllability of the direction of the magnetization 20m of the anisotropy variable unit 22 due to this injected spin, it may be preferable in some cases to apply a magnetic field in the Z direction (second direction) to the magnetization controller 20. The method of applying the magnetic field is not limited, and specific examples include placing a permanent magnet or an electromagnet near the variable magnetic field detection unit 100a, and providing an antiferromagnetic material capable of generating a magnetic field based on exchange coupling.

[0050] Since the anisotropy variable part 22 and the second layer 11 are magnetically coupled, the magnetization 11m of the second layer 11 is also oriented in the X1 direction.

[0051] Therefore, in the first state, the magnetization 11m of the second layer 11 of the magnetoresistive element 10a is fixed in the X1 direction. In this state, the variable magnetic field detecting unit 100a measures the measurement magnetic field H, and thereby outputs a first output.

[0052] (Second state) The second state shown in FIG. 5 is a state in which a second output is output from the variable magnetic field detection unit 100a. In the second state, the control current 20c of the spin torque generation unit 21 is oriented in the X1 direction, and the magnetization 11m of the second layer 11 is oriented in the X2 direction. The spin current 20s2 generated in the spin torque generation unit 21 by this current has a spin orientation opposite to that of the spin current 20s1 shown in FIG. 4. Therefore, the spins injected from the spin torque generation unit 21 to the anisotropy variable unit 22 are oriented in the opposite direction to that in the first state. Therefore, the magnetization 20m of the anisotropy variable unit 22, which is oriented by the spin orbit torque based on the injected spin, is oriented in the opposite direction to that in the first state (X2 direction). In other words, the reversal of the control current 20c of the spin torque generation unit 21 causes magnetization reversal in the anisotropy variable unit 22. Furthermore, because the anisotropy variable unit 22 and the second layer 11 are magnetically coupled, the magnetization 11m of the second layer 11 is also oriented in the X2 direction.

[0053] Therefore, in the second state, the magnetization 11m of the second layer 11 of the magnetoresistive element 10a is fixed in the X2 direction. In this state, the variable magnetic field detecting unit 100a measures the measurement magnetic field H, and a second output is output.

[0054] (First measurement method) FIG. 6 is a flowchart illustrating a first measurement method using the magnetic sensor according to the first embodiment of the present invention. In the first measurement method, as shown in FIG. 6, first, in a first measurement step, a control signal is output from the control power supply 3 to the control unit 7, causing the control power supply 3 to output a signal for setting the variable magnetic field detectors 100a, 100b, 100c, and 100d included in the magnetic field detector 2 to a first state. Specifically, the direction of the current flowing through the spin torque generator 21 of the magnetization controller 20 is set to a predetermined direction. In the magnetic field detector 2 shown in FIG. 2, the directions of the magnetization 11m of the second layer 11 of the two magnetoresistive elements 10b and 10c in the first state and the two magnetoresistive elements 10a and 10d in the second state are indicated by white arrows.

[0055] In this way, with the variable magnetic field detectors 100a, 100b, 100c, and 100d in the first or second state, the magnetoresistive elements 10a, 10b, 10c, and 10d measure the measured magnetic field H, and outputs are obtained from each of the variable magnetic field detectors 100a, 100b, 100c, and 100d. Based on these outputs, the magnetic field detector 2 outputs a first signal, a signal including a midpoint potential difference, which is the difference between the midpoint potential Va from the output terminal V1 and the midpoint potential Vb from the output terminal V2 (step S101). The signal including the midpoint potential difference output from the magnetic field detector 2 is input to the magnetic field calculator 4, and data representing these signals is stored in the magnetic field calculator 4 or in a memory (not shown). Note that the first signal may also be a signal including the midpoint potential Va and the midpoint potential Vb. In this case, data representing the two midpoint potentials is stored in the magnetic field calculator 4 or in a memory (not shown).

[0056] Next, in a second measurement step, a control signal output from the control unit 7 causes the control power supply 3 to output a signal for setting the variable magnetic field detectors 100a, 100b, 100c, and 100d included in the magnetic field detector 2 to the second state. Specifically, the direction of the current flowing through the spin torque generator 21 of the magnetization controller 20 is set to the opposite direction from that in the first state. FIG. 7 is an explanatory diagram of a magnetic field detector included in a magnetic sensor according to an embodiment of the present invention. In the magnetic field detector 2 shown in FIG. 7, the directions of 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 are indicated by white arrows, and these magnetizations are in the opposite direction from when the first signal is output.

[0057] In this way, with the variable magnetic field detectors 100a, 100b, 100c, and 100d in the first state or the second state, the magnetoresistive elements 10a, 10b, 10c, and 10d measure the measured magnetic field H, and outputs are obtained from each of the variable magnetic field detectors 100a, 100b, 100c, and 100d. Based on these signals, the magnetic field detector 2 outputs, as a second signal, a signal including a midpoint potential Va from the output terminal V1 and a signal including a midpoint potential Vb from the output terminal V2, or a signal representing the midpoint potential difference between these (step S102). The measurement times in steps S101 and S102 are both 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). For this reason, steps S101 and S102 are performed in an environment where the 1 / f noises are 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 in a memory (not shown) as data indicating these signals or data indicating a midpoint potential difference signal, which is the difference between the two signals.

[0058] Next, the magnetic field calculation unit 4 reads the data stored in the magnetic field calculation unit 4 or in a memory (not shown) in steps S101 and S102, and performs a process of calculating the difference between the midpoint potential indicated by the first signal and the midpoint potential indicated by the second signal, as a magnetic field calculation step (step S103). Note that if the data stored in the magnetic field calculation unit 4 or in 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 a midpoint potential difference from the data related to the first signal, obtains a signal including a midpoint potential difference from the data related to the second signal, and further performs a process of calculating the difference between these two signals including midpoint potential differences, as a magnetic field calculation step.

[0059] By performing the above processing by the magnetic field calculation unit 4, a measurement signal from which 1 / f noise has been appropriately removed is obtained. This measurement signal is amplified by the amplifier 5 and converted into a digital signal by the A / D conversion circuit 6. Therefore, since the measurement signal obtained by the measurement method using the magnetic sensor 1 according to this embodiment has 1 / f noise appropriately removed, the resolution (magnetic resolution) of the signal based on the measured magnetic field H is higher than that of the signal based on the first output (signal including the midpoint potential difference in the first state) and the signal based on the second output (signal including the midpoint potential difference in the second state).

[0060] In this embodiment, since the magnetic field detection unit 2 has a full bridge circuit 15, the signals to be processed to find the difference in the magnetic field calculation unit 4 are the signal of the midpoint potential difference in the first state based on the first output and the signal of the midpoint potential difference in the second state based on the second output, but the signals to be processed by the magnetic field calculation unit 4 are set appropriately depending on the output signal from the magnetic field detection unit 2. For example, if the magnetic field detection unit 2 has only one variable magnetic field detection unit 100a, the magnetic field calculation unit 4 will find the difference between the first output (first signal) and second output (second signal) from the variable magnetic field detection unit 100a.

[0061] (Another example of the first embodiment) Fig. 8 is a diagram illustrating another example of a variable magnetic field detector included in the magnetic sensor according to the first embodiment of the present invention. Fig. 9 is a diagram illustrating a first state of another example of a variable magnetic field detector of the magnetic sensor according to the first embodiment of the present invention. Fig. 10 is a diagram illustrating a second state of another example of a variable magnetic field detector of the magnetic sensor according to the first embodiment of the present invention.

[0062] In the example shown in FIG. 8, in contrast to the example shown in FIG. 3, the control wiring 61 is provided so that the current from the control current source I is applied to the spin torque generation unit 21 in the Y direction. In the first state, as shown in FIG. 9, the control current 20c is oriented in the Y1 direction, and the magnetization 20m of the anisotropy variable unit 22 is oriented in the X1 direction based on the spin current 20s1 generated thereby. Because the anisotropy variable unit 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 FIG. 10, the control current 20c is oriented in the Y2 direction, and the magnetization 20m of the anisotropy variable unit 22 is oriented in the X2 direction based on the spin current 20s2 generated thereby, which is opposite to the direction in the first state. Since the anisotropy variable part 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 X2 direction.

[0063] (Modification of the first embodiment) FIG. 11 is a diagram illustrating a modified example of the variable magnetic field detector included in the magnetic sensor according to the first embodiment of the present invention. In the example shown in FIG. 3 and other figures, the magnetization control unit 20 includes a spin torque generation unit 21 and an anisotropy variable unit 22. However, in the variable magnetic field detection unit 100a according to the modified example shown in FIG. 11, the magnetization control unit 20 is an integrated unit including an electromagnetization control unit 201 whose magnetization can be reversibly reversed by energizing. In this case, a control wiring 61 is connected to the electromagnetization control unit 201, and a current from a control current source I flows through the electromagnetization control unit 201, generating a spin current 20s1 and setting the direction of the magnetization 20m of the electromagnetization control unit 201 to a predetermined direction (the X1 direction in FIG. 11). As a result, the direction of the magnetization 11m of the second layer 11 magnetically coupled to the electromagnetization control unit 201 is also fixed to the X1 direction. The electromagnetization control unit 201 is not limited to a uniform structure and may have structural nonuniformity such as a layered structure or a dispersed structure.

[0064] (Second embodiment) 12 is a diagram illustrating an example of a variable magnetic field detection unit included in the 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 includes a variable second layer 111 that combines the functions of the second layer 11 and the anisotropy variable unit 22 of the variable magnetic field detection unit 100a of the magnetic sensor 1 and has a portion whose magnetization can be reversibly reversed based on the spin-orbit torque from the spin torque generation unit 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 includes the spin torque generation unit 21 but does not include the anisotropy variable unit 22.

[0065] 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 torque generation unit 21, and the variable second layer 111 may have a portion made of an antiferromagnetic material such as those exemplified as the constituent materials of the anisotropy variable unit 22. The variable second layer 111 may have a homogeneous structure, or may have a layered 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.

[0066] The method for controlling the first and second states in the variable magnetic field detector 100a of the magnetic sensor 1 according to the second embodiment of the present invention is the same as that in the variable magnetic field detector 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 torque generator 21, and the direction of the magnetization 111m of the variable second layer 111 is set depending on the direction of the control current 20c flowing through the spin torque generator 21. Therefore, by flowing the control current 20c in opposite directions, a first output, which is the output of the variable magnetic field detector 100a in the first state, and a second output, which is the output of the variable magnetic field detector 100a in the second state, can be obtained. Note that FIG. 12 illustrates the first state, as in FIG. 4. In FIG. 12, the control wiring 61 is arranged so that the control current 20c applied to the spin torque generator 21 is oriented in the X1 direction or the X2 direction. However, this is not limited thereto, and the control wiring 61 may be arranged so that the control current 20c is oriented in the Y1 direction or the Y2 direction.

[0067] (Third embodiment) 13 is a diagram illustrating an example of a variable magnetic field detector included in the magnetic sensor according to the third embodiment of the present invention. The variable magnetic field detector 100a of the magnetic sensor 1 according to the third embodiment of the present invention differs from the variable magnetic field detector 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 detector 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 it includes a current-variable second layer 112 having a portion whose magnetization can be reversibly reversed by generating a spin-orbit torque therein using a current from a control wiring 61.

[0068] The material constituting the current variable second layer 112 is not particularly limited as long as it is a material whose magnetization can be reversed depending on the direction of current flow, and the current variable second layer 112 may have a portion made of an antiferromagnetic material such as the examples of materials constituting the anisotropy variable section 22. The current variable second layer 112 may have a homogeneous structure, or may have a layered structure or dispersed structure of portions made of different materials. Furthermore, the current variable second layer 112 may have a heterogeneous structure in which its composition changes continuously or stepwise.

[0069] The method for controlling 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 in 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 current second layer 112 instead of the spin torque generation unit 21 in the first embodiment, and the direction of the magnetization 112m of the variable current second layer 112 is set by the direction of the control current 20c passed through the variable current second layer 112. Therefore, by passing the control current 20c in opposite directions, it is possible to obtain 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. Note that FIG. 13 shows the first state, as in FIG. 9. In FIG. 13, the control wiring 61 is arranged so that the control current 20c applied to the spin torque generation unit 21 is oriented in the Y1 direction or the Y2 direction, but this is not limited to this, and the control wiring 61 may be arranged so that the control current 20c is oriented in the X1 direction or the X2 direction.

[0070] (Second measurement method) Fig. 14 is a diagram illustrating a second measurement method (first state) using the magnetic sensor according to the first embodiment of the present invention. Fig. 15 is a diagram illustrating a second measurement method (second state) using the magnetic sensor according to the first embodiment of the present invention. In the second measurement method, the flowchart is the same as the flowchart of the first measurement method shown in Fig. 6, but the configuration of the magnetic field detection unit 2A included in the magnetic sensor 1 is different.

[0071] In the second measurement method, as shown in FIG. 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 related 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 their second layers 11 are magnetized in opposite directions. In FIG. 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 oriented in the X2 direction, and the magnetization 11m of the second layer 11 of the second variable magnetic field detection unit 102 is oriented in the X1 direction. The first layers 13 of the first variable magnetic field detection unit 101 and the second variable magnetic field detection unit 102 are both set to be aligned in the same direction when not subjected to the measurement magnetic field H. In Fig. 14, as shown by the black arrow, 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 (a permanent magnet, an induced magnetic field source, or a structure that generates exchange coupling) not shown.

[0072] The magnetic field calculation unit 4 performs arithmetic processing using the electrical signal from the output unit VA as input to calculate the measured magnetic field H. This arithmetic processing includes finding 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 in one direction of 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 in the other direction of the first direction.

[0073] Specifically, first, in a first measurement step, a control signal is output from the control power supply 3 to the control unit 7, causing the control power supply 3 to output a signal for setting the first variable magnetic field detection unit 101 and the second variable magnetic field detection unit 102 included in the magnetic field detection unit 2A to a first state. Specifically, the direction of the current flowing through the spin torque generation unit 21 of the magnetization control unit 20 is set to a predetermined direction. In Fig. 14, the directions 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 are indicated by outline arrows.

[0074] In this way, the first variable magnetic field detecting unit 101 and the second variable magnetic field detecting unit 102 are set to the first state, and the first variable magnetic field detecting unit 101 and the second variable magnetic field detecting unit 102 measure the measurement magnetic field H, and a first electric signal is obtained from the output unit VA (step S101). The first electric signal is input to the magnetic field calculating unit 4 and stored in the magnetic field calculating unit 4 or in a memory (not shown).

[0075] Next, in a second measurement step, a control signal is output from the control power supply 3 to the control unit 7, causing the control signal to set the first variable magnetic field detection unit 101 and the second variable magnetic field detection unit 102 included in the magnetic field detection unit 2A to the second state. Specifically, the direction of the current flowing through the spin torque generation unit 21 of the magnetization control unit 20 is set to the opposite direction to that in the first state. FIG. 15 is an explanatory diagram (second state) of the magnetic field detection unit included in the magnetic sensor according to one embodiment of the present invention. In FIG. 15, the directions of the magnetizations 11m of the second layers 11 of the first variable magnetic field detection unit 101 and the second variable magnetic field detection unit 102 in the second state are indicated by white arrows, and these magnetizations 11m are opposite to those in the first state.

[0076] In this way, the first variable magnetic field detecting unit 101 and the second variable magnetic field detecting unit 102 are set to the second state, the first variable magnetic field detecting unit 101 and the second variable magnetic field detecting unit 102 measure the measured magnetic field H, and a second electric signal is obtained from the output unit VA (step S102). The second electric signal is input to the magnetic field calculating unit 4 and stored in the magnetic field calculating unit 4 or a memory (not shown).

[0077] Next, the magnetic field calculation unit 4 performs a process of calculating the difference between the first electric signal and the second electric signal stored in the magnetic field calculation unit 4 or in 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 a measurement signal obtained by the full-bridge circuit 15 using the half-bridge circuit 16. Therefore, the magnetic field detection unit 2A of the second measurement method can have a smaller device area than when measurement is performed by the first measurement method using the magnetic field detection unit 2 having the full-bridge circuit 15.

[0078] Furthermore, in the full-bridge circuit 15, an ideal output is obtained when the electrical characteristics of the four magnetoresistive effect elements 10a, 10b, 10c, and 10d are exactly the same. However, in reality, the four elements are manufactured differently, and therefore differences in electrical characteristics are unavoidable. These differences contribute to a decrease in measurement accuracy in the full-bridge circuit 15. In contrast, the second measurement method uses half the number of elements compared to the full-bridge circuit 15, and therefore reduces the decrease in measurement accuracy caused by variations in the electrical characteristics of the elements. Therefore, by combining the second measurement method with the first measurement method, it is possible to particularly improve the magnetic resolution of the magnetic sensor 1.

[0079] Fig. 16 is a detailed explanatory diagram of the state (non-energization control state) shown in Fig. 3. In the state shown in Fig. 16, the control unit 7 performs control so as not to flow the control current 20c from the control current source I to the spin torque generation unit 21. As a result, the magnetization control unit 20 of the variable magnetic field detection unit 100a of the magnetic field detection unit 2 is controlled so that the spin torque generation unit 21 does not generate a spin orbit torque.

[0080] Here, in a specific example, the spin torque generation unit 21 has a portion made of an antiferromagnetic material. Therefore, when no spin-orbit torque is generated, a magnetic field resulting from exchange coupling 21af generated between this antiferromagnetic portion and the anisotropy variable portion 22 acts as a bias magnetic field, causing magnetization 22m in the Y2 direction in the anisotropy variable portion 22. Since the anisotropy variable portion 22 and the second layer 11 are magnetically coupled, magnetization 11m in the Y2 direction is also generated in the second layer 11. In other words, the exchange coupling 21af based on the portion made of an antiferromagnetic material (antiferromagnetic portion) in the spin torque generation unit 21 is a second-layer bias magnetic field source, and exerts a bias magnetic field on the second layer 11 when no spin-orbit torque is generated from the spin torque generation unit 21 due to control by the control current source I not to flow the control current 20c.

[0081] 16, in a non-energized state in which the control unit 7 controls the control current source I not to supply the control current 20c and the magnetization 11m of the second layer 11 is maintained in the first direction, Y2, the variable magnetic field detection unit 100a has no measurement sensitivity (is insensitive) 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 non-energized state, the variable magnetic field detection unit 100a has the sensitivity axis in the Y direction.

[0082] 4 and 5, when the control unit 7 controls the control current 20c to flow from the control current source I to the spin torque generation unit 21, the magnetization 11m of the second layer 11 enters a current control state in which it is maintained in the second direction, that is, the X1 direction (FIG. 4) or the X2 direction (FIG. 5). In the current 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 current control state, the variable magnetic field detection unit 100a has the sensitivity axis in the X direction.

[0083] 17 is a flowchart illustrating a third measurement method using the magnetic sensor according to the first embodiment of the present invention. In the third measurement method, as shown in FIG. 17, first, in the magnetic sensor 1, a control signal output from the control unit 7 causes the control power supply 3 to output a signal for placing the second layer 11 of the variable magnetic field detection unit 100a included in the magnetic field detection unit 2 in a non-conductive control state as a first measurement step. Specifically, the control current 20c is not passed through the spin torque generation unit 21 of the magnetization control unit 20.

[0084] In this way, the second layer 11 of the variable magnetic field detecting unit 100a is brought into a non-energized controlled state, the magnetoresistive element 10a measures the measurement magnetic field H' along the Y direction, and the variable magnetic field detecting unit 100a outputs a first output (step S111). The first signal output from the variable magnetic field detecting unit 100a is input to the magnetic field calculating unit 4, and data indicating the first signal is stored in the magnetic field calculating unit 4 or a memory (not shown).

[0085] Next, in a second measurement step, a signal for controlling the second layer 11 of the variable magnetic field detection unit 100a included in the magnetic field detection unit 2 to be in a current-carrying state is output from the control power supply 3 in response to a control signal output from the control unit 7. Specifically, a control current 20c is passed through the spin torque generation unit 21 of the magnetization control unit 20.

[0086] In this way, the second layer 11 of the variable magnetic field detector 100a is brought into a current-carrying control state, the magnetoresistive element 10a measures the measurement magnetic field H along the X direction, and the variable magnetic field detector 100a outputs a second output (step S112). The two signals output from the magnetic field detector 2 are input to the magnetic field calculator 4, and data indicating the second signals is stored in the magnetic field calculator 4 or in a memory (not shown).

[0087] The measurement times for steps S111 and S112 are both sufficiently shorter than 1 microsecond (for example, 0.01 microseconds), and the time required for steps S111 and S112 is also sufficiently shorter than 1 microsecond (for example, 0.03 microseconds). Therefore, steps S111 and S112 measure substantially the same measurement magnetic field applied to the variable magnetic field detection unit 100a, and 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.

[0088] Next, the magnetic field calculation unit 4 reads out the data stored in the magnetic field calculation unit 4 or a memory (not shown) in steps S111 and S112, and performs a process of calculating the actual measured magnetic field from the first output and the second output as a magnetic field calculation step (step S113). In the magnetic field calculation step, the strength of the actual measured magnetic field may be calculated, or the direction of the actual measured magnetic field may be calculated. When calculating the direction of the measured magnetic field, for example, the relative angle in the XY plane may be calculated based on the first direction (Y2 direction) measured in the non-energized control state.

[0089] 18 is a diagram illustrating in detail one example (modification) of the variable magnetic field detection unit included in the magnetic sensor according to the first embodiment of the present invention. In the configuration shown in Fig. 16, the anisotropy variable unit 22 has a portion made of an antiferromagnetic material (antiferromagnetic portion), and the exchange coupling 22af based on this antiferromagnetic portion serves as a second-layer bias magnetic field source that applies a bias magnetic field to the second layer 11. However, in the configuration shown in Fig. 18, the exchange coupling 22af based on the portion made of an antiferromagnetic material (antiferromagnetic portion) in the anisotropy variable unit 22 serves as a second-layer bias magnetic field source that applies a bias magnetic field to the second layer. Specifically, when the control unit 7 controls so as not to supply the control current 20c from the control current source I, the exchange coupling 22af based on the antiferromagnetic portion of the anisotropy variable unit 22 generates a 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 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.Therefore, in one specific example of this modified example, the relative angle in the YZ plane can be obtained based on the first orientation (Y2 orientation) measured in the non-energized state.

[0090] When the magnetic field detection unit 2 has a variable magnetic field detection unit 100a having the configuration shown in FIG. 16 and a variable magnetic field detection unit 100b having the configuration shown in FIG. 18 (for example, as the variable magnetic field detection unit 100b), the magnetic field calculation unit 4 can calculate the three-dimensional orientation of the actually applied measurement magnetic field (for example, the three-dimensional relative angle with respect to the first orientation (Y2 orientation) of the variable magnetic field detection unit 100a). In conventional technology, three magnetic field detection elements with sensitivity axes in the X, Y, and Z directions are required to calculate the three-dimensional orientation of the measurement magnetic field. However, with the above configuration, the three-dimensional orientation can be measured using the two variable magnetic field detection units 100a and 100b. Moreover, since both of the two variable magnetic field detection units 100a and 100b measure the same unidirectional component of the measurement magnetic field (the X direction in this example), the relative angles of the two variable magnetic field detection units 100a and 100b can be corrected based on these results. Therefore, the magnetic sensor 1 according to this embodiment can measure angles with higher accuracy than magnetic sensors according to conventional techniques.

[0091] The above-described embodiments are provided to facilitate understanding of the present invention and are not intended to limit the present invention. Therefore, the elements disclosed in the above embodiments are intended to encompass all design modifications and equivalents 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. However, this is not limited to this. The magnetization 11m of the second layer 11 may be reversed by a spin transfer torque, or 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 the variable second layer 111 and the current-variable second layer 112, which combine 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 are likely to contribute to the reversal of the magnetization 11m of the second layer 11.

[0092] The present invention includes the following aspects. (1) 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 layer and the second layer, and a magnetization control unit that changes the direction of magnetization of the second layer, wherein the second layer is reversibly switchable between a non-energized control state in which the magnetization is maintained in a first direction even when subjected to the measurement magnetic field, and an energized control state in which the magnetization is maintained in a second direction different from the first direction even when subjected to the measurement magnetic field. (2) The magnetic sensor according to (1), wherein the first orientation and the second orientation are along directions different from each other. (3) A magnetic sensor as described in (2) above, wherein the first orientation is along a first orthogonal direction, which is one of the directions orthogonal 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 that is orthogonal to the stacking direction and intersects with the first orthogonal direction. (4) The magnetic sensor according to (3), wherein the first orthogonal direction and the second orthogonal direction are orthogonal to each other. (5) A magnetic sensor as described in (2) above, wherein the first direction 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 direction is along the stacking direction. (6) A magnetic sensor as described in (2) above, wherein the first direction is along a stacking direction in which the first layer and the second layer are aligned, and the second direction is along a first orthogonal direction, which is one of the directions perpendicular to the stacking direction. (7) The magnetic sensor according to (2), wherein the measured magnetic field has a component along the first direction and a component along the second direction. (8) The magnetic sensor described in (2) above further includes a magnetic field calculation unit that calculates the intensity of the measured magnetic field based on a first output from the variable magnetic field detection unit when the second layer is in the non-energized control state and a second output from the variable magnetic field detection unit when the second layer is in the energized control state. (9) A magnetic sensor as described in (2) above, 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 non-energized control state and a second output from the variable magnetic field detection unit when the second layer is in the energized control state. (10) The magnetic sensor described in (1) above, further comprising a second layer bias magnetic field source that applies a magnetic field to the second layer in order to maintain the magnetization of the second layer in the first orientation in the non-energized control state. (11) The magnetic sensor according to (10) above, wherein the magnetization control section has an antiferromagnetic section made of antiferromagnetic material, and exchange coupling based on the antiferromagnetic section serves as the second layer bias magnetic field source. (12) The magnetic sensor according to (10), wherein the second layer bias magnetic field source includes at least one of a coil that generates an induced magnetic field when energized and a permanent magnet. (13) The magnetic sensor according to (10), wherein the second layer bias magnetic field source and the second layer are aligned in a stacking direction in which the first layer and the second layer are aligned. (14) The magnetic sensor according to (10), wherein the second layer bias magnetic field source and the second layer are aligned in a direction intersecting a stacking direction in which the first layer and the second layer are aligned. (15) The magnetic sensor according to (1), wherein in the non-energized state, the magnetization of the second layer is maintained in the first direction based on shape magnetic anisotropy. (16) The magnetic sensor described in (1) above, wherein the magnetization control unit has a spin torque generation unit that generates a spin orbit torque when current is applied, and the magnetization direction of the second layer is reversibly changed based on the spin orbit torque from the spin torque generation unit. (17) The magnetic sensor described in (16) above, wherein the magnetization control unit has a magnetic anisotropy and an anisotropy variable unit that can reversibly change the direction of magnetization based on the spin-orbit torque from the spin torque generation unit, and the anisotropy variable unit is magnetically coupled to the second layer. (18) The magnetic sensor according to (17), wherein the anisotropy variable portion has a portion made of an antiferromagnetic material. (19) The magnetic sensor described in (16) above, wherein the second layer is a variable second layer having a portion that can reversibly change the direction of magnetization based on the spin-orbit torque from the spin torque generation portion. (20) The magnetic sensor according to (19), wherein the variable second layer has a portion made of an antiferromagnetic material. (21) The magnetic sensor described in (1) above, wherein the second layer is a current-variable second layer that is integrated with the magnetization control unit and has a portion made of an antiferromagnetic material that can reversibly change the direction of the magnetization when current is applied. (22) The magnetic sensor according to (1), wherein the magnetization control section is an electromagnetization control section that can reversibly change the direction of the magnetization of the second layer by energizing. (23) A magnetic measurement method using a magnetic sensor including: a variable magnetic field detection unit having a magnetoresistive element having a first layer that can be magnetized in a direction along the measurement magnetic field, a second layer that can maintain its 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; a magnetization control unit that changes the direction of the magnetization of the second layer; and a magnetic field calculation unit that calculates the measurement magnetic field based on a first output from the variable magnetic field detection unit when the magnetization of the second layer is maintained in a first direction and a second output from the variable magnetic field detection unit when the magnetization of the second layer is maintained in a second direction different from the first direction, the magnetic measurement 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; and a third step of calculating the measurement magnetic field in the magnetic field calculation unit based on the first output and the second output. (24) The magnetic measurement method described in (23) above, wherein the first direction and the second direction are along different directions, and the direction of the measured magnetic field is calculated based on the first output and the second output. [Industrial Applicability]

[0093] The present invention is useful as a magnetic sensor with high magnetic resolution that can detect an external magnetic field with high sensitivity. [Explanation of symbols]

[0094] 1: Magnetic sensor 2, 2A: Magnetic field detection unit 3: Control power supply 4: Magnetic field calculation section 5: Amplifier 6: A / D conversion circuit 7: Control section 10P: Detection center 10a, 10b, 10c, 10d: magnetoresistive effect elements 11: 2nd layer 12: Non-magnetic layer 13: 1st layer 15: Full bridge circuit 16: Half-bridge circuit 20: Magnetization control section 21: Spin torque generation unit 22: Anisotropic variable section 61: Control wiring 62: Measurement wiring 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 second layer 20c: Control current 11m, 13m, 20m, 111m, 112m: Magnetization 21af, 22af: Exchange coupling 20s1, 20s2: spin current 201 Electromagnetic control unit 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 variable magnetic field detection unit including 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 magnetization control unit that changes the direction of magnetization of the second layer; The second layer is a non-energized control state in which the magnetization is maintained in a first direction even when the measurement magnetic field is applied; a current control state in which the magnetization is maintained in a second direction different from the first direction even when the measurement magnetic field is applied; A magnetic sensor characterized by being capable of reversibly switching between:

2. The magnetic sensor according to claim 1 , wherein the first orientation and the second orientation are along different directions.

3. 3. The magnetic sensor of claim 2, wherein the first orientation is along a first orthogonal direction, which is one of 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 that is perpendicular to the stacking direction and intersects with the first orthogonal direction.

4. The magnetic sensor according to claim 3 , wherein the first orthogonal direction and the second orthogonal direction are orthogonal to each other.

5. 3. The magnetic sensor according to claim 2, wherein the first direction is along a first orthogonal direction that is one of directions perpendicular to a stacking direction in which the first layer and the second layer are aligned, and the second direction is along the stacking direction.

6. 3. The magnetic sensor according to claim 2, wherein the first orientation is along a stacking direction in which the first layer and the second layer are aligned, and the second orientation is along a first orthogonal direction that is one of directions perpendicular to the stacking direction.

7. The magnetic sensor of claim 2 , wherein the measured magnetic field has a component along the first orientation and a component along the second orientation.

8. The magnetic sensor of claim 2, further comprising a magnetic field calculation unit that calculates the intensity of the measured magnetic field based on a first output from the variable magnetic field detection unit when the second layer is in the non-energized control state and a second output from the variable magnetic field detection unit when the second layer is in the energized control state.

9. 3. The magnetic sensor of claim 2, 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 non-energized control state and a second output from the variable magnetic field detection unit when the second layer is in the energized control state.

10. 2. The magnetic sensor according to claim 1, 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 the first orientation in the non-energized control state.

11. The magnetic sensor according to claim 10 , wherein the magnetization control section has an antiferromagnetic section made of antiferromagnetic material, and exchange coupling based on the antiferromagnetic section serves as a source of the second layer bias magnetic field.

12. The magnetic sensor according to claim 10 , wherein the second layer bias magnetic field source includes at least one of a coil that generates an induced magnetic field when energized and a permanent magnet.

13. The magnetic sensor according to claim 10 , wherein the second layer bias magnetic field source and the second layer are aligned in a stacking direction in which the first layer and the second layer are aligned.

14. The magnetic sensor according to claim 10 , wherein the second layer bias magnetic field source and the second layer are aligned in a direction intersecting a stacking direction in which the first layer and the second layer are aligned.

15. The magnetic sensor according to claim 1 , wherein in the non-energized state, the magnetization of the second layer is maintained in the first direction based on shape magnetic anisotropy.

16. 2. The magnetic sensor of claim 1, wherein the magnetization control unit has a spin torque generation unit that generates a spin orbit torque when current is applied, and the magnetization direction of the second layer is reversibly changed based on the spin orbit torque from the spin torque generation unit.

17. 17. The magnetic sensor of claim 16, wherein the magnetization control unit has an anisotropy variable unit that has magnetic anisotropy and can reversibly change the direction of magnetization based on the spin-orbit torque from the spin torque generation unit, and the anisotropy variable unit is magnetically coupled to the second layer.

18. 18. The magnetic sensor according to claim 17, wherein the anisotropy variable portion has a portion made of an antiferromagnetic material.

19. The magnetic sensor according to claim 16 , wherein the second layer is a variable second layer having a portion that can reversibly change the orientation of the magnetization based on the spin-orbit torque from the spin torque generation portion.

20. 20. The magnetic sensor of claim 19, wherein the deformable second layer has a portion made of antiferromagnetic material.

21. 2. The magnetic sensor according to claim 1, wherein the second layer is a variable current second layer that is integrated with the magnetization control section and has a portion made of an antiferromagnetic material that can reversibly change the direction of the magnetization when current is applied.

22. The magnetic sensor according to claim 1 , wherein the magnetization control section is an electromagnetization control section that can reversibly change the direction of the magnetization of the second layer by energizing the magnetization control section.

23. a variable magnetic field detection unit including 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 magnetization control unit that changes the direction of magnetization of the second layer; 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 maintained in a first orientation and a second output from the variable magnetic field detection unit when the magnetization of the second layer is maintained in a second orientation different from the first orientation; A magnetic measurement method using a magnetic sensor comprising: a first step of outputting the first output from the variable magnetic field detection unit; a second step of outputting the second output from the variable magnetic field detection unit; a third step of calculating the measured magnetic field based on the first output and the second output in the magnetic field calculation unit; To be prepared A magnetic measurement method comprising:

24. the first orientation and the second orientation are along different directions; The magnetic measurement method according to claim 23 , further comprising calculating a direction of the measured magnetic field based on the first output and the second output.

Images