Magnetic sensor and magnetic measurement method

Abstract

To provide a magnetic sensor and magnetic measurement method capable of measuring a small magnetic field with high accuracy by removing 1 / f noise.SOLUTION: A magnetic sensor comprises a variable magnetic field detection unit including a Hall element having a magnetically sensitive direction representing an anomalous Hall effect, and a magnetic field control unit for controlling the Hall element so that a magnetic field having a component in an insensitive direction perpendicular to the magnetically sensitive direction is generated in the Hall element. The magnetic sensor may further include a magnetic field calculation unit for calculating a measurement magnetic field on the basis of a first output including a measurement result when the variable magnetic field detection unit measures the measurement magnetic field along the magnetically sensitive direction in a first state where the direction of the magnetic field generated in the Hall element is not controlled by the magnetic field control unit, and a second output including a measurement result when the variable magnetic field detection unit measures the measurement magnetic field in a second state where the direction of the magnetic field generated in the Hall element is controlled by the magnetic field control unit.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] As a magnetic sensor for detecting and measuring a magnetic field, there is one provided with a magnetoresistive effect element using a GMR (giant magnetoresistance) effect or a TMR (tunnel magnetoresistance) effect. The magnetoresistive effect element in these magnetic sensors has a configuration in which a fixed magnetic layer, a nonmagnetic intermediate layer, and a free magnetic layer are laminated in this order. In the magnetoresistive effect 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 effect element can detect a magnetic field by using the resistance change of the magnetoresistive effect element.

[0003] A magnetic sensor provided with a magnetoresistive effect element has 1 / f noise that cannot be removed by a filter. Since 1 / f noise is inversely proportional to the frequency and increases as the frequency decreases, 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 the voltage difference to the low-frequency side and removing the frequency band of the voltage difference that is greatly affected by 1 / f noise.

[0006] Patent Document 3 discloses a magnetic field sensing device that samples a bridge signal for a first current and a second current by switching between two sampling and hold modes, 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 polarity of the sensor signal and then takes 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 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 [Overview of the project] [Problems that the invention aims to solve]

[0009] Magnetic sensors equipped with magnetoresistive elements have a problem in which 1 / f noise in the low-frequency range reduces the detection accuracy of the magnetic sensor. Various devices and methods have been proposed to solve this problem. The present invention aims to provide a magnetic sensor equipped with a magnetoresistive element and a magnetic measurement method that can remove 1 / f noise with a configuration different from conventional ones and measure small magnetic fields with high accuracy. [Means for solving the problem]

[0010] In one embodiment, the present invention is a magnetic sensor characterized by comprising a variable magnetic field detection unit having a Hall element having a magnetic sensing direction that exhibits an abnormal Hall effect, and a magnetic field control unit that controls the Hall element so that a magnetic field having a component in a non-sensitive direction perpendicular to the magnetic sensing direction is generated in the Hall element.

[0011] Magnetic sensors using Hall elements have been able to improve their magnetic detection sensitivity by utilizing the anomalous Hall effect based on ferromagnets. Furthermore, in recent years, materials capable of generating virtual magnetic fields, such as topological antiferromagnets, have been discovered, and by using such materials as constituent materials for Hall elements, it is expected that the magnetic detection sensitivity of magnetic sensors using Hall elements will be further improved. By adding a magnetic field control unit to a magnetic sensor with a Hall element that has improved magnetic detection sensitivity, it becomes possible to apply noise reduction measures such as interphase double sampling (CDS). This can particularly improve the magnetic resolution of the magnetic sensor.

[0012] The above magnetic sensor may further include a magnetic field calculation unit that calculates the measured magnetic field based on: a first output including the measurement result when the variable magnetic field detection unit measures a measurement magnetic field along the magnetic sensing direction in a first state in which the direction of the magnetic field generated in the Hall element is not controlled by the magnetic field control unit; and a second output including the measurement result when the variable magnetic field detection unit measures the measurement magnetic field in a second state in which the direction of the magnetic field generated in the Hall element is controlled by the magnetic field control unit. When the magnetic field generated in the Hall element controlled by the magnetic field control unit in the second state has a component in the insensitive direction perpendicular to the magnetic sensing direction, preferably along the insensitive direction, the intensity of the measured magnetic field in the second output is weaker than the intensity of the measured magnetic field in the first output, so 1 / f noise can be removed by CDS using the first output and the second output.

[0013] In the magnetic sensor described above, the magnetic field control unit may generate a spin-orbit torque when energized, in which case the Hall element generates a magnetic field having a component in the insensitive direction based on the spin-orbit torque.

[0014] In the magnetic sensor described above, the Hall element and the magnetic field control unit are electrically connected, and the circuit that supplies current to the magnetic field control unit and the circuit that measures the Hall voltage generated in the Hall element may be common in at least part. This makes it possible to miniaturize the magnetic sensor.

[0015] In the magnetic sensor described above, the magnetic field calculation unit may perform a process that includes subtracting from the first output a second adjustment output obtained by removing from the second output a signal corresponding to the voltage applied to the magnetic field control unit to control the Hall element, thereby obtaining a signal indicating the measured magnetic field.

[0016] In the magnetic sensor described above, the Hall element and the magnetic field control unit may be magnetically coupled. This allows the magnetic field control unit to stably control the magnetic state of the Hall element.

[0017] In the above-described magnetic sensor, a bias magnetic field source may be provided that sets the magnetic field generated in the Hall element in a direction intersecting the magnetic sensing direction when no measuring magnetic field is applied. This can reduce the hysteresis of the magnetic sensor.

[0018] In the magnetic sensor described above, the Hall element and the magnetic field control unit may form a laminated structure. In this case, the magnetic field control unit is made up of a laminated structure comprising a spin torque generating unit that generates a spin orbit torque when energized, and an anisotropy variable unit that generates a magnetic field having a component in the insensitive direction based on the spin orbit torque from the spin torque generating unit, and the anisotropy variable unit may be magnetically coupled to the Hall element.

[0019] In the magnetic sensor forming the above-described laminated structure, the magnetic field control unit includes an energized magnetic field control unit that generates a magnetic field having a component in the insensitive direction by energization, and the energized magnetic field control unit may be magnetically coupled to the Hall element. The relationship between the lamination direction (element lamination direction) of the Hall element and the magnetic field control unit, the magnetic sensitive direction, and the insensitive direction is set as appropriate. Either one of the magnetic sensitive direction and the insensitive direction may be along the element lamination direction, or both the magnetic sensitive direction and the insensitive direction may be orthogonal to the element lamination direction.

[0020] As another aspect of the present invention, there is provided a magnetic measurement method using a magnetic sensor including a variable magnetic field detection unit that measures a measurement magnetic field and a magnetic field calculation unit that calculates the measurement magnetic field based on an output from the variable magnetic field detection unit. The variable magnetic field detection unit includes a Hall element having a magnetic sensitive direction exhibiting an anomalous Hall effect, and a magnetic field control unit that controls the Hall element so that a magnetic field having a component in the insensitive direction orthogonal to the magnetic sensitive direction is generated in the Hall element. Such a magnetic measurement method includes a first measurement step of obtaining a first output including a measurement result in a first state in which the direction of the magnetic field generated in the Hall element is not controlled by the magnetic field control unit from the variable magnetic field detection unit, a second measurement step of obtaining a second output including a measurement result in a second state in which the direction of the magnetic field generated in the Hall element is controlled by the magnetic field control unit from the variable magnetic field detection unit, and a magnetic field calculation step of calculating the measurement magnetic field from the first output and the second output in the magnetic field calculation unit.

Effect of the Invention

[0021] According to the present invention, since 1 / f noise can be removed from the measurement magnetic field, it is possible to provide a magnetic sensor and a magnetic measurement method having a high magnetic resolution capable of measuring a small magnetic field with high accuracy.

Brief Description of the Drawings

[0022] [Figure 1] It is a block diagram of a magnetic sensor according to an embodiment of the present invention. [Figure 2]This figure illustrates the variable magnetic field detection unit (no magnetic field state) of a magnetic sensor according to the first embodiment of the present invention. [Figure 3] This figure illustrates the variable magnetic field detection unit (Hall element in the first state) of a magnetic sensor according to the first embodiment of the present invention. [Figure 4] This figure illustrates the variable magnetic field detection unit (Hall element in second state) of a magnetic sensor according to the first embodiment of the present invention. [Figure 5] This is a flowchart illustrating a magnetic measurement method using a magnetic sensor according to the first embodiment of the present invention. [Figure 6] This is a timing chart illustrating a magnetic measurement method using a magnetic sensor according to the first embodiment of the present invention. [Figure 7] This is an explanatory diagram of a modified example of the variable magnetic field detection unit included in the magnetic sensor according to the first embodiment of the present invention. [Figure 8] This figure illustrates a first example (no magnetic field state) of a variable magnetic field detection unit included in a magnetic sensor according to a second embodiment of the present invention. [Figure 9] This figure illustrates a first example of a variable magnetic field detection unit (Hall element in a first state) included in a magnetic sensor according to a second embodiment of the present invention. [Figure 10A] This figure illustrates a first example of a variable magnetic field detection unit (Hall element in second state) included in a magnetic sensor according to a second embodiment of the present invention. [Figure 10B] Figure 10A is an XY planar diagram illustrating the Lorentz force acting on the current flowing through the Hall element shown. [Figure 11] This figure illustrates a second example of a variable magnetic field detection unit (Hall element in second state) included in a magnetic sensor according to a second embodiment of the present invention. [Modes for carrying out the invention]

[0023] 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.

[0024] 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 variable magnetic field detection unit (no magnetic field state) of the magnetic sensor according to one embodiment of the present invention. The magnetic sensor 1 of this embodiment includes a variable 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.

[0025] The variable magnetic field detection unit 2 detects the external magnetic field (measured magnetic field H) to be measured, and includes a magnetic field control unit 20 that controls the Hall element 10 exhibiting an abnormal Hall effect and the magnetic field 10m generated in the Hall element 10, as will be described later. The control power supply 3 applies a predetermined current or voltage to each part based on a control signal from the control unit 7, and includes a supply power supply Vb and a measurement power supply Vm, which will be described later.

[0026] The magnetic field calculation unit 4 calculates the measured magnetic field H based on the output of the variable magnetic field detection unit 2, and is composed of, for example, a CDS (Correlated Double Sampling) circuit. The magnetic field calculation unit 4 calculates the measured magnetic field H based on the first output from the variable magnetic field detection unit 2 when the Hall element 10 (described later) is in the first state, and the second output from the variable magnetic field detection unit 2 when the Hall element 10 is in the second state. For example, 1 / f noise can be removed from the first output by determining the difference between the signal based on the first output and the signal based on the second output.

[0027] In the magnetic sensor 1, the magnetic field calculation unit 4 calculates the measurement magnetic field H, then the signal corresponding to the calculated measurement magnetic field H is amplified by the amplifier 5, and then converted into digital data by the A / D conversion circuit 6.

[0028] (First Embodiment) Figure 2 illustrates the variable magnetic field detection unit (no magnetic field state) of the magnetic sensor according to the first embodiment of the present invention. Figure 3 illustrates the variable magnetic field detection unit (Hall element in the first state) of the magnetic sensor according to the first embodiment of the present invention. Figure 4 illustrates the variable magnetic field detection unit (Hall element in the second state) of the magnetic sensor according to the first embodiment of the present invention.

[0029] The variable magnetic field detection unit 2 of the magnetic sensor 1 according to this embodiment includes a Hall element 10 having a magnetically sensitive direction that exhibits an abnormal Hall effect, and a magnetic field control unit 20 that controls the Hall element 10 so that a magnetic field 10m having a component in a dead direction perpendicular to the magnetically sensitive direction is generated in the Hall element 10. In this embodiment, the magnetically sensitive direction of the Hall element 10 is along the Z direction, which is along the stacking direction (element stacking direction) of the Hall element 10 and the magnetic field control unit 20. The dead direction is the direction of an external magnetic field in which the Hall element 10 does not exhibit an abnormal Hall effect, and as described above, the two directions (X direction and Y direction) perpendicular to the magnetically sensitive direction are the dead directions. In this embodiment, the case in which the dead direction is along the X direction, which is one of the directions perpendicular to the element stacking direction, is used as a specific example.

[0030] The material constituting the Hall element 10 is not limited as long as it is possible to induce an anomalous Hall effect in the Hall element 10 when subjected to a magnetic field in the direction of magnetism. Specific examples of such materials include ferromagnetic materials such as Fe-Ni alloys and Fe-Si alloys, Heusler alloys such as Co2MnAl, semimagnetic semiconductors such as CdMnTe, magnetic Weyl semimetals such as Co3Sn2S2, Mn3X (X=Sn, Ge, Ga, Rh, Pt, Ir), and Mn 1-x Tr x Examples include antiferromagnetic materials such as those with a gamma phase (Tr=Ni,Fe, Cu, Ru, Pd, Ir, Rh, Pd, Pt).

[0031] The magnetic field 10m generated in the Hall element 10 exhibiting the anomalous Hall effect may be based on the magnetization of the material constituting the Hall element 10, or it may be based on a virtual magnetic field generated by the magnetic structural characteristics of the material constituting the Hall element 10. In the former case (magnetization), a ferromagnetic material is exemplified as the constituent material of the Hall element 10, and in the latter case (virtual magnetic field), a topological antiferromagnetic material is exemplified as the constituent material of the Hall element 10.

[0032] In this embodiment, both the Hall element 10 and the magnetic field control unit 20 are film-like bodies and have a laminated structure stacked in the Z direction. The Hall element 10 may be composed of a single layer film or a multilayer film. If it is a multilayer film, boundary regions may be generated between adjacent films. Also, if it is a multilayer film, at least one of the constituent films must be made of a material that exhibits an anomalous Hall effect.

[0033] The Hall element 10 is connected to a first circuit 60, which is provided with a power supply Vb for supplying a charge that receives a Lorentz force F to the Hall element 10, and a second circuit 61 for measuring the Hall voltage generated in the Hall element 10 when the charge receives the Lorentz force F. The measuring power supply Vm provided in the second circuit 61 has a voltage measurement function. In this embodiment, the electrodes related to the first circuit 60 are provided at both ends of the Hall element 10 in the X direction. Also, in this embodiment, since the Hall element 10 and the magnetic field control unit 20 are electrically connected, the electrodes related to the second circuit 61 are provided at both ends of a part of the magnetic field control unit 20 (the spin torque generation unit 21, which will be described later) in the Y direction.

[0034] In this embodiment, the magnetic field control unit 20 generates a spin-orbit torque when energized, and based on the spin-orbit torque, a magnetic field 10m having a component in the X direction (dead direction) is generated in the Hall element 10. In this embodiment, the magnetic field control unit 20 is composed of a spin torque generation unit 21 that generates a spin-orbit torque when energized, and an anisotropy variable unit 22 that generates a magnetic field 20m having a component in the X direction (dead direction) based on the spin-orbit torque from the spin torque generation unit 21, stacked together. The anisotropy variable unit 22 is magnetically coupled to the Hall element 10, thereby allowing the spin torque generation unit 21 to control the direction of the magnetic field 10m generated in the Hall element 10 via the anisotropy variable unit 22.

[0035] The spin torque generation unit 21 applies a spin orbit torque to the anisotropy variable unit 22 by energizing it in the XY plane direction, and in this embodiment, in the Y direction, thereby exhibiting effects such as the spin Hall effect and the Rashba-Edelstein effect. The materials constituting the spin torque generation unit 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 x Examples 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.

[0036] In one specific example shown in Figure 2, the spin torque generating unit 21 is a film-like body, which may be a single structure, i.e., composed of a single layer film, or a multilayer film. If it is a multilayer film, boundary regions may be formed between adjacent films. The spin torque generating unit 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 torque generating unit 21.

[0037] The anisotropy variable unit 22 can generate a magnetic field 20m having a component in the X direction (the insensitive direction in this embodiment) based on the spin-orbit torque from the spin-torque generation unit 21 (see Figure 4). Furthermore, since the anisotropy variable unit 22 is magnetically coupled to the Hall element 10, when a magnetic field 20m is generated in the anisotropy variable unit 22 based on the spin-orbit torque from the spin-torque generation unit 21, a magnetic field 10m having a component in the X direction (the insensitive direction) is also generated in the Hall element 10 (see Figure 4). Note that in Figure 2, no spin-orbit torque is applied from the spin-torque generation unit 21 to the anisotropy variable unit 22, and no measuring magnetic field H is applied, so the magnetic field 20m of the anisotropy variable unit 22 may be oriented towards X1 due to the influence of the magnetic field 10m of the magnetically coupled Hall element 10.

[0038] The anisotropy variable section 22 may be made of any material as long as it can receive spin-orbit torque and generate a magnetic field having an X direction (dead direction). The anisotropy variable section 22 may be made of a ferromagnetic material or an antiferromagnetic material. Examples of such materials include soft magnetic materials such as CoFe alloys and NiFe alloys (nickel-iron alloys); and antiferromagnetic materials such as Mn3X (X=Sn, Ge, Ga, Rh, Pt, Ir).

[0039] In one specific example shown in Figure 2, the anisotropic variable portion 22 is a film-like body, which may be a single structure, i.e., composed of a single layer film, or a multilayer film. If it is a multilayer film, boundary regions may be formed between adjacent films. The anisotropic variable portion 22 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 anisotropic variable portion 22.

[0040] In this embodiment, a permanent magnet layer 30 serving as a bias magnetic field source is stacked on the Hall element 10. In a no-magnetic-field state where no measurement magnetic field H is applied, as shown in Figure 2, the direction of the magnetic field 10m generated in the Hall element 10 is aligned with the direction of the magnetization 30m of the permanent magnet layer 30 (X1 direction). This direction of the magnetic field 10m (X direction) is one of the insensitive directions and is parallel to the direction of the current 10c flowing to the Hall element 10 due to the power supply Vb of the first circuit 60. Therefore, no Lorentz force acts on the charge (electrons) of the current 10c, and no Hall voltage is generated based on the magnetic field 10m. Furthermore, the bias magnetic field based on the magnetization 30m of the permanent magnet layer 30 makes it easy for the material constituting the Hall element 10 to become uniformly magnetized. Therefore, the hysteresis characteristics of the magnetic sensor 1 tend to be good. Note that the bias magnetic field source is not limited to a permanent magnet, but may also be a structure that generates a magnetic field based on an induced magnetic field due to coil energization or an exchange coupling involving an antiferromagnetic material.

[0041] (First state) The first state shown in Figure 3 is a state in which the direction of the magnetic field 10m generated in the Hall element 10 is not controlled by the magnetic field control unit 20, and in the first state, the variable magnetic field detection unit 2 outputs a first output including the measurement result when the measurement magnetic field H along the Z direction (magnetic sensing direction) is measured.

[0042] In this embodiment, a current 10c from a power supply Vb that provides electrons as charges subject to the Lorentz force F flows through the Hall element 10 in the direction X2. In this state, when the Hall element 10 receives a measurement magnetic field H in the Z direction (magnetic sensing direction), a magnetic field 10m with a large component in the Z direction is generated in the Hall element 10, causing the Hall element 10 to exhibit the anomalous Hall effect. If the constituent material of the Hall element 10 is a ferromagnetic material, the magnetic field 10m includes the magnetization of the Hall element 10. If the constituent material of the Hall element 10 is a topological antiferromagnetic material, the magnetic field 10m includes a virtual magnetic field originating from the Berry curvature existing in reciprocal lattice space. Since the strength of the thus generated magnetic field 10m is greater than the measurement magnetic field H, the Hall element 10 exhibiting the anomalous Hall effect has an amplification function for the measurement magnetic field H.

[0043] This magnetic field of 10m causes a Lorentz force F in the direction of Y2 to act on the electrons carrying the current 10c. As mentioned above, since the Hall element 10 and the magnetic field control unit 20 are electrically connected, the Hall voltage based on the Lorentz force F generated in the Hall element 10 is measured in the second circuit 61, which is equipped with a measuring power supply Vm having a voltage measuring function, through an electrode provided at the Y-direction end of the magnetic field control unit 20, and a signal including this measurement result is output as the first output from the variable magnetic field detection unit 2.

[0044] When the relative permeability of the anisotropy variable section 22 is greater than 1, the anisotropy variable section 22 is magnetized by the measurement magnetic field H, and the magnetic field 20m generated in the anisotropy variable section 22 due to this magnetization extends to the Hall element 10, helping to generate a predetermined magnetic field 10m in the Hall element 10. In other words, in this case, the anisotropy variable section 22 functions as a yoke for the Hall element 10.

[0045] Furthermore, since the magnetization 30m of the permanent magnet layer 30 acts on the Hall element 10 even in the first state, the magnetic field 10m generated in the Hall element 10 may have a component in the direction of X1 due to the influence of the magnetization 30m. Even in this case, the direction of the magnetization 30m (X direction) is parallel to the direction of the current 10c and is one of the insensitive directions, so no Hall voltage is generated based on the magnetization 30m. In other words, the magnetization 30m of the permanent magnet layer 30 does not affect the measured value of the measured magnetic field H included in the first output.

[0046] (Second state) The second state shown in Figure 4 is a state in which the direction of the magnetic field 10m generated in the Hall element 10 is controlled by the magnetic field control unit 20, and the variable magnetic field detection unit 2 outputs a second output including the measurement result when the measured magnetic field H is measured in the second state.

[0047] In this embodiment, in the second state, the current 20c from the second circuit 61 having a measuring power supply Vm is directed in the Y1 direction. This current 20c generates a spin current 20s in the spin torque generation unit 21, and the spin orbit torque generated by this spin current 20s generates a magnetic field 20m in the X1 direction in the anisotropy variable unit 22. Influenced by the magnetic field 20m generated in the anisotropy variable unit 22, the magnetic field 10m generated in the Hall element 10 magnetically coupled to the anisotropy variable unit 22 has a component in the X1 direction along the magnetic field 20m that is larger than the component in the Z1 direction along the measuring magnetic field H. That is, a strong magnetic field is generated in the Hall element 10 along the X direction (insensitive direction). As a result, the Hall element 10 does not exhibit the abnormal Hall effect even when subjected to the measuring magnetic field H along the Z direction (magnetically sensitive direction), and the sensitivity of the measuring magnetic field H decreases. Specifically, as can be understood by comparing Figures 3 and 4, in the second state, the Lorentz force F acting on the current 10c flowing through the Hall element 10 becomes smaller than in the first state. As a result, the Hall voltage measured in the second circuit 61 becomes smaller, and a signal including this measurement result is output from the variable magnetic field detection unit 2 as the second output.

[0048] Furthermore, the magnetization 30m of the permanent magnet layer 30 acts on the Hall element 10 even in the second state. However, since the direction of the magnetization 30m (X direction) is parallel to the direction of the magnetic field 20m of the anisotropy variable section 22 and is one of the insensitive directions, the magnetization 30m, together with the magnetic field 20m, contributes to the magnetic field 10m having a component in the X direction (insensitive direction).

[0049] (Magnetic measurement method) Figure 5 is a flowchart illustrating a magnetic measurement method using a magnetic sensor according to the first embodiment of the present invention. Figure 6 is a timing chart illustrating a magnetic measurement method using a magnetic sensor according to the first embodiment of the present invention. In this measurement method, as shown in Figure 5, first, as a first measurement step, the control power supply 3 is controlled by a control signal output from the control unit 7 so that the Hall element 10 of the variable magnetic field detection unit 2 enters a first state. Specifically, the control unit 7 controls the measurement power supply Vm so that no current 20c flows to the magnetic field control unit 20.

[0050] With the Hall element 10 in the first state, a current 10c is supplied to the Hall element 10 from the power supply Vb, and the voltage is measured at the measuring power supply Vm. The measured voltage is equal to the Hall voltage generated in the Hall element 10. A signal including this measurement result is output from the variable magnetic field detection unit 2 as the first output (step S101). The data indicating the first output output from the variable magnetic field detection unit 2 is input to the magnetic field calculation unit 4 and stored in the magnetic field calculation unit 4 or a memory (not shown).

[0051] Next, as a second measurement step, the control power supply 3 is controlled by a control signal output from the control unit 7 so that the Hall element 10 of the variable magnetic field detection unit 2 enters a second state. Specifically, the control unit 7 controls the measurement power supply Vm so that a current 20c flows to the magnetic field control unit 20.

[0052] In this way, the Hall element 10 is set to the second state, and a current 10c is passed from the supply power Vb to the Hall element 10, and the voltage is measured at the measuring power Vm. The measured voltage is equal to the sum of the voltage Vs applied to the magnetic field control unit 20 to pass a current 20c and the Hall voltage generated in the Hall element 10. A signal including this measurement result is output from the variable magnetic field detection unit 2 as the second output (step S102). The data indicating the first output output from the variable magnetic field detection unit 2 is input to the magnetic field calculation unit 4 and stored in the magnetic field calculation unit 4 or a memory (not shown).

[0053] The measurement times for both steps S101 and S102 are both well less than 1 microsecond (e.g., 0.01 microseconds), and the time required for steps S101 and S102 is also well less 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 output and the 1 / f noise contained in the second output are substantially equal.

[0054] In the timing chart shown in Figure 6, the Hall element 10 alternates between a first state and a second state at predetermined intervals. Specifically, the Hall element 10 is first set to the first state, and the Hall voltage generated by the magnetic field 10m based on the anomalous Hall effect is measured at the measurement power supply Vm, and the result becomes the first output. Subsequently, in the second state, a voltage Vs for spin torque generation is applied from the measurement power supply Vm to set the Hall element 10 to the second state (see Figure 6(a)), and the voltage including this voltage Vs is measured at the measurement power supply Vm, and the result becomes the second output (see Figure 6(b)).

[0055] In steps S101 and S102, the magnetic field calculation unit 4 reads data stored in the magnetic field calculation unit 4 or a memory (not shown) and performs a magnetic field calculation step (step S103) to determine the measured magnetic field H based on the signal based on the first output and the signal based on the second output. In this process, not only is the second output subtracted from the first output, but the voltage Vs included in the second output is first removed, thereby obtaining the second adjusted output. The timing chart shown in Figure 6(c) shows the voltage V1 based on the first output and the voltage V2 based on the second adjusted output. By taking the difference between the first output and the second adjusted output (V1-V2), 1 / f noise is appropriately removed from the voltage ΔV.

[0056] As the magnetic field calculation unit 4 performs the above processing, a measurement signal with 1 / f noise 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. Thus, the measurement signal obtained by the magnetic measurement method using the magnetic sensor 1 according to this embodiment has 1 / f noise appropriately removed, and therefore 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 or the signal based on the second output.

[0057] (modified version) Figure 7 is an explanatory diagram of a modified example of the variable magnetic field detection unit of the magnetic sensor according to the first embodiment of the present invention, in which the Hall element is in the second state. The variable magnetic field detection unit 2 shown in Figure 7 differs from the variable magnetic field detection unit 2 shown in Figure 2 in that the magnetic field control unit 20 does not have a stacked structure of a spin torque generation unit 21 and an anisotropy variable unit 22, but rather has an electromagnetic field control unit 201 in which these functions are integrated, that is, an electromagnetic field control unit 201 that generates a magnetic field 201m having a component in the X direction (dead direction) when energized. Specifically, when a current 201c flows in the Y1 direction, a spin current 201s in the Z1 direction is generated in the electromagnetic field control unit 201, and based on this spin current 201s, a magnetic field 201m in the X1 direction is generated in the electromagnetic field control unit 201. Since the electromagnetic field control unit 201 and the Hall element 10 are magnetically coupled, the magnetic field 201m in the X1 direction generated in the electromagnetic field control unit 201 causes the Hall element 10 to enter the second state, and a magnetic field 10m in the X1 direction is generated.

[0058] Since Figure 7 shows a no-magnetic-field state, the magnetic field 10m generated in the Hall element 10 in the second state is almost parallel to the magnetic field 201m generated in the electromagnetic field control unit 201. In this state, even if a measurement magnetic field H in the direction of Z1 is applied, a component in the direction of Z1 is unlikely to be generated in the magnetic field 10m of the Hall element 10, and the Hall voltage generated in the Hall element 10 is low.

[0059] (Second Embodiment) Figure 8 illustrates an example of a variable magnetic field detection unit (no magnetic field state) included in a magnetic sensor according to a second embodiment of the present invention. Figure 9 illustrates a first example of a variable magnetic field detection unit (Hall element in a first state) included in a magnetic sensor according to a second embodiment of the present invention. Figure 10A illustrates a first example of a variable magnetic field detection unit (Hall element in a second state) included in a magnetic sensor according to a second embodiment of the present invention. Figure 10B is an XY plan view illustrating the Lorentz force acting on the current flowing through the Hall element shown in Figure 10A.

[0060] In the variable magnetic field detection unit 2 of the magnetic sensor 1 according to the second embodiment, as shown in Figure 8, the basic structure (a structure in which a Hall element 10, a magnetic field control unit 20 having a spin torque generation unit 21 and an anisotropy variable unit 22, and a permanent magnet layer 30 are stacked) is the same as that of the variable magnetic field detection unit 2 according to the first embodiment, but the direction of the magnetic field based on the anomalous Hall effect in the Hall element 10 is different, being in the X direction. That is, the direction of magnetization in which the Hall element 10 exhibits the anomalous Hall effect is along the Z direction in the first embodiment, but along the X direction in the second embodiment.

[0061] Based on this difference, the direction of the measured magnetic field H, the arrangement of the electrodes in the first circuit 60, the magnetization direction of the permanent magnet layer 30, and the direction of the magnetic field 20m generated in the anisotropy variable section 22 are different. In the first example of the second embodiment, a magnetic field 20m along the Y direction is generated in the anisotropy variable section 22 by the spin orbit torque from the spin torque generation section 21. That is, in this example, both the magnetizing direction and the desensitizing direction are perpendicular to the stacking direction (Z direction) of the Hall element 10 and the magnetic field control section 20, and specifically, the magnetizing direction is along the X direction and the desensitizing direction is along the Y direction.

[0062] In the variable magnetic field detection unit 2 according to the second embodiment, as shown in Figure 8, the electrodes of the first circuit 60 are provided at the end in the stacking direction (Z direction) of the laminate, which is formed by stacking the Hall element 10, the magnetic field control unit 20, and the permanent magnet layer 30. Therefore, in the Hall element 10, the current 10c from the power supply Vb for the first circuit 60 is directed in the Z2 direction. Furthermore, the magnetization 30m of the permanent magnet layer 30 is directed in the Z direction. For this reason, in a no-magnetic-field state, a magnetic field 10m is generated in the Hall element 10 along the Z1 direction due to the influence of the magnetization 30m of the permanent magnet layer 30.

[0063] (First state) As shown in Figure 9, in the first state when the spin torque generation unit 21 is not energized, when a measurement magnetic field H is applied in the direction of X1, an anomalous Hall effect occurs in the Hall element 10 in response to the measurement magnetic field H. As a result, a magnetic field 10m with a large component in the direction of X1 along the magnetic sensing direction is generated in the Hall element 10, and the Hall element 10 exhibits an anomalous Hall effect. Due to this magnetic field 10m, a Lorentz force F in the direction of Y1 acts on the charge (electrons) of the current 10c, and a Hall voltage is generated in the Y direction. By measuring this Hall voltage in the second circuit 61, the first output is obtained.

[0064] Furthermore, since the magnetization 30m of the permanent magnet layer 30 acts on the Hall element 10 even in the first state, the magnetic field 10m generated in the Hall element 10 may have a component in the Z1 direction due to the influence of the magnetization 30m. Even in this case, the direction of the magnetization 30m (Z direction) is parallel to the direction of the current 10c and is one of the insensitive directions, so no Hall voltage is generated based on the magnetization 30m. In other words, the magnetization 30m of the permanent magnet layer 30 does not affect the measured value of the measured magnetic field H included in the first output.

[0065] (Second state) As shown in Figure 10A, in this embodiment, in the second state, the current 20c from the second circuit 61 having a measuring power supply Vm is directed in the Y1 direction. This current 20c generates a spin current 20s in the Z1 direction in the spin torque generation unit 21, and the spin orbit torque generated by this spin current 20s generates a magnetic field 20m in the Y2 direction along the insensitive direction in the anisotropy variable unit 22. Influenced by the magnetic field 20m generated in the anisotropy variable unit 22, the magnetic field 10m generated in the Hall element 10 magnetically coupled to the anisotropy variable unit 22 has a component in the Y2 direction along the magnetic field 20m that is larger than the component in the X1 direction along the measuring magnetic field H. That is, a strong magnetic field is generated in the Hall element 10 along the Y direction (insensitive direction). As a result, the Hall element 10 does not exhibit the abnormal Hall effect even when subjected to the measuring magnetic field H along the X direction (magnetically sensitive direction), and the sensitivity of the measuring magnetic field H decreases. Specifically, as shown in the XY plan view of the Hall element 10 depicted in Figure 10B, in the second state, the Lorentz force F acting on the current 10c flowing through the Hall element 10 has a component in the X1 direction that is larger than the component in the Y1 direction. As a result, the Hall voltage measured in the second circuit 61 becomes smaller, and a signal including this measurement result is output from the variable magnetic field detection unit 2 as the second output.

[0066] (Another example of the second embodiment) Figure 11 illustrates a second example of a variable magnetic field detection unit (Hall element in second state) of a magnetic sensor according to the second embodiment of the present invention. The variable magnetic field detection unit 2 according to this example differs from the variable magnetic field detection unit 2 according to the first example of the second embodiment in that the direction of the magnetic field 20m generated in the anisotropic variable unit 22 by the spin-orbit torque from the spin-torque generation unit 21 is along the Z direction. That is, in the second example of the second embodiment, the magnetic sensing direction is along the X direction, which is one of the directions perpendicular to the element stacking direction (Z direction), and the desensitizing direction is along the Z direction, which is along the element stacking direction.

[0067] Therefore, in this example, in the second state, when a current 20c in the Y1 direction flows through the spin torque generation unit 21 due to the energization from the second circuit 61 having a measurement power supply Vm, a magnetic field 20m in the Z1 direction is generated in the anisotropy variable unit 22. Influenced by the magnetic field 20m generated in the anisotropy variable unit 22, the magnetic field 10m generated in the Hall element 10, which is magnetically coupled to the anisotropy variable unit 22, has a Z1 component that is larger than the X1 component that is along the measurement magnetic field H. In other words, a strong magnetic field is generated in the Hall element 10 along the Z direction (insensitive direction). As a result, the Hall element 10 does not exhibit the anomalous Hall effect even when subjected to the measurement magnetic field H along the X direction (magnetically sensitive direction), and the sensitivity of the measurement magnetic field H decreases. Specifically, as can be understood by comparing Figure 9 and Figure 11, in the second state, the Lorentz force F acting on the current 10c flowing through the Hall element 10 is smaller than in the first state. As a result, the Hall voltage measured in the second circuit 61 becomes smaller, and a signal including this measurement result is output from the variable magnetic field detection unit 2 as the second output.

[0068] Furthermore, the magnetization 30m of the permanent magnet layer 30 acts on the Hall element 10 even in the second state. However, since the direction of the magnetization 30m (Z1 direction) is the same as the direction of the magnetic field 20m of the anisotropy variable section 22, the magnetization 30m, together with the magnetic field 20m, contributes to the magnetic field 10m having a component in the Z direction (insensitive direction).

[0069] 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 magnetic field control unit 20 controls the magnetic field 10m of the Hall element 10 by spin-orbit torque, but is not limited to this, and the magnetic field 10m of the Hall element 10 may be controlled by spin-transition torque, and both spin-orbit torque and spin-transition torque may contribute to the control of the magnetic field 10m of the Hall element 10. In particular, when the magnetic field control unit 20 is equipped with a through-electromagnetic field control unit 201, it may be preferable to control the magnetic field 10m of the Hall element 10 by both spin-orbit torque and spin-transition torque. [Industrial applicability]

[0070] 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. [Explanation of symbols]

[0071] 1: Magnetic sensor 2: Variable magnetic field detection unit 3: Control power supply 4: Magnetic field calculation unit 5: Amplifier 6: A / D conversion circuit 7: Control Unit 10: Hall element 10c, 20c, 201c: current 10m, 20m, 201m: Magnetic field 20: Magnetic field control unit 20s, 201s: Spin current 21: Spin Torque Generation Unit 22: Anisotropic variable part 30: Permanent magnet layer 30m: magnetized 60:1st circuit 61: 2nd circuit 201: Electromagnetic Field Control Unit F: Lorentz force H: Magnetic field being measured V1, V2, Vs, ΔV: Voltage Vb: Supply power Vm: power supply for measurement

Claims

1. A Hall element having a magnetically sensitive direction that exhibits an abnormal Hall effect, A magnetic field control unit controls the magnetic field generated in the Hall element, which has a component in the unresponsive direction perpendicular to the magnetic sensing direction, It is equipped with a variable magnetic field detection unit having In a first state where the direction of the magnetic field generated in the Hall element is not controlled by the magnetic field control unit, the first output includes the measurement result when the variable magnetic field detection unit measures the magnetic field along the magnetic sensing direction, In a second state in which the direction of the magnetic field generated in the Hall element is controlled by the magnetic field control unit, the variable magnetic field detection unit measures the measured magnetic field and the second output includes the measurement result, A magnetic sensor further comprising a magnetic field calculation unit that calculates the measured magnetic field based on the above.

2. The magnetic sensor according to claim 1, wherein the magnetic field control unit generates a spin-orbit torque when energized, and the Hall element generates a magnetic field having a component in the insensitive direction based on the spin-orbit torque.

3. The Hall element and the magnetic field control unit are electrically connected, The magnetic sensor according to claim 1, wherein the circuit that supplies current to the magnetic field control unit and the circuit that measures the Hall voltage generated in the Hall element are common in at least part.

4. The magnetic sensor according to claim 1, wherein the magnetic field calculation unit performs a process that includes subtracting from the first output a second adjustment output obtained by removing from the second output a signal corresponding to the voltage applied to the magnetic field control unit for controlling the Hall element, thereby obtaining a signal indicating the measured magnetic field.

5. The magnetic sensor according to claim 1, wherein the Hall element and the magnetic field control unit are magnetically coupled.

6. The magnetic sensor according to claim 1, further comprising a bias magnetic field source that sets the bias magnetic field generated in the Hall element in a direction intersecting the magnetic sensing direction when no measuring magnetic field is applied.

7. The magnetic sensor according to claim 1, wherein the Hall element and the magnetic field control unit form a laminated structure.

8. The magnetic field control unit, A spin torque generation unit that generates spin orbit torque when power is applied, An anisotropic variable unit that generates a magnetic field having a component in the insensitive direction based on the spin orbit torque from the spin torque generation unit, These are stacked together, The magnetic sensor according to claim 7, wherein the anisotropic variable portion is magnetically coupled to the Hall element.

9. The magnetic field control unit has an electromagnetic field control unit that generates a magnetic field having a component in the insensitive direction when energized, and the electromagnetic field control unit is magnetically coupled to the Hall element, as described in claim 7.

10. The magnetic sensor according to claim 7, wherein the magnetic sensing direction is along the stacking direction of the Hall element and the magnetic field control unit.

11. The magnetic sensor according to claim 7, wherein both the magnetic sensing direction and the desensitizing direction are perpendicular to the stacking direction of the Hall element and the magnetic field control unit.

12. The magnetic sensor according to claim 7, wherein the insensitive direction is aligned with the stacking direction of the Hall element and the magnetic field control unit.

13. The magnetic sensor according to claim 6, wherein the bias magnetic field source has a portion made of an antiferromagnetic material and is magnetically coupled to the Hall element, and the bias magnetic field is based on exchange coupling involving the antiferromagnetic material.

14. The magnetic sensor according to claim 13, wherein the magnetic field control unit has a portion made of the antiferromagnetic material.

15. The magnetic field control unit, A spin torque generation unit that generates spin orbit torque when power is applied, An anisotropic variable unit that generates a magnetic field having a component in the insensitive direction based on the spin orbit torque from the spin torque generating unit, These are stacked together, The magnetic sensor according to claim 14, wherein the anisotropic variable portion has a portion made of the antiferromagnetic material and is magnetically coupled to the Hall element.

16. The magnetic sensor according to claim 13, wherein the Hall element has a portion made of the antiferromagnetic material.

17. A magnetic measurement method using a magnetic sensor comprising a variable magnetic field detection unit for measuring a magnetic field and a magnetic field calculation unit for calculating the magnetic field based on the output from the variable magnetic field detection unit, The aforementioned variable magnetic field detection unit is A Hall element having a magnetically sensitive direction that exhibits an abnormal Hall effect, The Hall element comprises a magnetic field control unit that controls the magnetic field having a component in the unresponsive direction perpendicular to the magnetic sensing direction, A first measurement step of obtaining a first output from the variable magnetic field detection unit, which includes a measurement result in a first state in which the direction of the magnetic field generated in the Hall element is not controlled by the magnetic field control unit, A second measurement step of obtaining a second output from the variable magnetic field detection unit, which includes a measurement result in a second state in which the direction of the magnetic field generated in the Hall element is controlled by the magnetic field control unit, The magnetic field calculation step in the magnetic field calculation unit calculates the measured magnetic field from the first output and the second output, A magnetic measurement method characterized by comprising the following:

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