ANOMAL HALL SENSOR AND ANOMAL HALL DETECTION METHOD

Abstract

The present disclosure relates to an anomalous Hall sensor (100) comprising a Hall cross (110). The Hall cross (110) comprises a stack of layers (200) with a ferromagnetic layer (210). A first arm (114-1) of the Hall cross formed in the stack of layers extends in a first direction. A second arm (114-2) of the Hall cross formed in the stack of layers extends in a second direction perpendicular to the first direction. The anomalous Hall sensor (100) comprises a control circuit (120) configured to apply current through the first arm (114-1) of the Hall cross and measure voltage across the second arm (114-2) of the Hall cross in response to the current through the first arm, and to apply current through the second arm (114-2) of the Hall cross and measure voltage across the first arm (114-1) of the Hall cross in response to the current through the second arm.The anomalous Hall sensor (100) further comprises a processor (130) configured to calculate, based on a combination of the measured voltages, a component of an external magnetic field in a third direction, perpendicular to the first and second directions.

Description

Area

[0001] The present disclosure relates generally to the field of magnetic field sensing and, more particularly, to the field of 3-dimensional (3D) magnetic field measurement. background

[0002] In magnetic field sensors, a small offset can be crucial to fully exploit the signal-to-noise ratio and reduce unwanted environmental dependencies. This is especially true for measuring small signals, such as Earth's magnetic fields in a compass application or high-precision 3D magnetic sensing. Offset compensation techniques are well-established for Hall-based devices, but are lacking for magnetoresistive devices, which generally offer a higher signal-to-noise ratio. Furthermore, to be able to measure fields in all three directions (x, y, z), separate dedicated devices are typically used for each direction, increasing the design and manufacturing complexity and the size of the sensing circuitry.

[0003] Conventional 3D Hall sensors require three different sensitive elements to detect fields in all three directions. These sensors have a limited signal-to-noise ratio but allow active offset compensation via spinning current techniques. Using spin-orbit torque (SOT), the concept of a 3D magnetic field sensor with a single sensitive element was introduced in Li, Ruofan, et al., "A spin-orbit torque device for sensing three-dimensional magnetic fields." Nature Electronics 4.3 (2021): 179-184. However, the domain wall used can lead to noise and irreproducible behavior. If the domain wall is annihilated by the sensor due to strong external magnetic fields, the sensor response can change or even destroy its functional behavior.

[0004] SOT can manifest itself in various systems, including magnetic materials and structures. When an electric current is passed through a heavy metal or a layered structure made of different materials, a spin-orbit interaction or coupling can generate a torque on the magnetization of adjacent magnetic layers.

[0005] DE 10 2022 208 712 A1 describes a magnetic sensor device that uses SOT to improve sensitivity to external magnetic fields. The sensor device uses a stack of magnetic layers to detect the components of magnetic fields in the x, y, and z directions. The sensor device exhibits insensitivity to orthogonal stray fields and reduced offset sensitivity. The sensor sensitivity can be fine-tuned by adjusting the current to ensure optimal functionality.

[0006] In a conventional Hall effect, when an electric current flows through a conducting material placed in a magnetic field perpendicular to the current, a transverse voltage known as the Hall voltage is induced across the material. This voltage is proportional to the product of the applied current, the magnetic field strength, and a material-dependent parameter called the Hall coefficient. However, in materials with strong spin-orbit coupling and magnetization, such as ferromagnetic metals or magnetic semiconductors, an additional contribution arises due to the anomalous Hall effect (AHE). The AHE is related to the spin-dependent scattering of charge carriers within the material. It causes an asymmetry in the charge carrier trajectories, leading to a deflection of the charge carriers and the appearance of an additional Hall voltage perpendicular to the applied current and magnetic field.

[0007] Thus, there is a need to improve spin-orbit torque devices or anomalous Hall sensors using the AHE. Summary

[0008] This need is addressed by devices and methods according to the independent claims. Potentially advantageous embodiments are addressed by the dependent claims.

[0009] According to a first aspect, the present disclosure proposes an anomalous Hall sensor using the AHE. The anomalous Hall sensor comprises a Hall cross. The Hall cross comprises a layer stack comprising at least one ferromagnetic layer next to at least one further layer. There may be several possible implementations of the layer stack. A first arm of the Hall cross formed in the layer stack extends in a first direction. The first direction may, for example, be referred to as the x-direction. A second arm of the Hall cross formed in the layer stack extends in a second direction perpendicular to the first direction. The second direction may, for example, be referred to as the y-direction.The anomalous Hall sensor further comprises a control circuit configured to apply current(s) through the first arm of the Hall cross and to measure voltage(s) across the second arm of the Hall cross in response to the current(s) through the first arm. The control circuit is further configured to apply current(s) through the second arm of the Hall cross and to measure voltage(s) across the first arm of the Hall cross in response to the current(s) through the second arm. The anomalous Hall sensor further comprises a processor configured to calculate, based on a combination of the measured voltages, a component of an external magnetic field in a third direction perpendicular to the first and second directions. The third direction may, for example, be referred to as the z-direction.

[0010] Thus, the present disclosure proposes a spinning current technique for anomalous Hall sensors. By applying respective currents to the two arms of the Hall cross, the component of the external magnetic field in the third direction perpendicular to the first and second directions can be determined.

[0011] The Hall cross can comprise a layered structure (e.g., rectangular, square, or cross-shaped) with four electrical contacts arranged in a cross-like pattern. The first arm of the Hall cross connects two of the four contacts in the first direction (e.g., x-direction), while the second arm of the Hall cross connects the other two of the four contacts in the second direction (e.g., y-direction).

[0012] In some embodiments, the control circuit is configured to apply a first and a second current through the first arm of the Hall cross in opposite directions and to measure a respective first and second voltage across the second arm of the Hall cross in response to the respective currents. When the first direction is the x-direction, the first and second currents may be in the positive x-direction and negative x-direction. The control circuit may further be configured to apply a third and a fourth current through the second arm of the Hall cross in opposite directions and to measure a respective third and fourth voltage across the first arm of the Hall cross in response to the respective currents. When the second direction is the y-direction, the third and fourth currents may be currents in the positive y-direction and negative y-direction.The processor may be configured to calculate the component of the external magnetic field in the third direction (e.g., z-direction) based on a combination of the four measured voltages. The combination of the four measured voltages may, for example, include a first difference between the third and fourth voltages and a second difference between the first and second voltages. In a particular implementation, the combination of the four measured voltages may correspond to a difference between the second difference and the first difference.

[0013] In some embodiments, the processor is further configured to calculate a component of the external magnetic field in the first direction (e.g., x-direction) based on a combination of the measured first and second voltages in response to the respective currents. For example, the processor may be configured to calculate the component of the external magnetic field in the first direction (e.g., x-direction) based on a sum of the measured first and second voltages.

[0014] In some embodiments, the processor is further configured to calculate a component of the external magnetic field in the second direction (e.g., y-direction) based on a combination of the measured third and fourth voltages in response to the respective currents. For example, the processor may be configured to calculate the component of the external magnetic field in the second direction (e.g., y-direction) based on a sum of the measured third and fourth voltages.

[0015] Thus, an anomalous 3D Hall sensor can be obtained.

[0016] In some embodiments, the layer stack comprises at least one conductive non-magnetic layer and the ferromagnetic layer formed one above the other. The conductive non-magnetic layer may, for example, comprise a heavy metal layer. Some examples of heavy metals that can be used in spin-torque devices include: Platinum (Pt): Platinum is a heavy metal widely used in spintronics due to its strong spin-orbit coupling and good electrical conductivity. It can be used as a spin current source or spin sink layer in spintronic devices.

[0017] Tantalum (Ta): Tantalum is another heavy metal that exhibits strong spin-orbit coupling and is used in spintronic applications. It can be used as a spin-sink layer in devices to efficiently absorb spin currents. Ruthenium (Ru): Ruthenium is a heavy metal that offers good spin-orbit coupling and is used in spintronic devices, particularly magnetic tunnel junctions (MTJs) and spin-transfer torque devices. Palladium (Pd): While not as widely used as platinum, palladium is another heavy metal that can generate spin currents due to its strong spin-orbit coupling. It has been investigated for its potential in spintronic applications.

[0018] Some examples of ferromagnetic materials that can be used in spin torque devices include: Permalloy (NiFe): Permalloy, a ferromagnetic alloy of nickel and iron, can be used in spin-torque devices due to its favorable magnetic properties, such as high saturation magnetization and low magnetic damping. It is often used as the free layer or reference layer in spin-transfer torque magnetic random access memory (STT-MRAM) and magnetic tunnel junctions (MTJs).

[0019] Cobalt (Co) and cobalt alloys: Cobalt and its alloys, such as CoFeB (cobalt-iron-boron), can be used in spin-torque devices. They possess strong magnetic anisotropy and are often used as the reference layer in STT-MRAM and magnetic sensors.

[0020] Rare-earth transition metal alloys: Certain rare-earth transition metal alloys, such as gadolinium iron garnet (GdIG), have been investigated for their use in spin-torque devices. These materials exhibit interesting magnetic and spintronic properties that may be advantageous for certain applications.

[0021] In spin-torque devices, a spin current can be injected from a heavy metal layer into a neighboring ferromagnetic layer. The spin current exerts a torque on the magnetization of the ferromagnetic layer, thus enabling the control and manipulation of its orientation.

[0022] In some embodiments, the layer stack comprises a multilayer comprising a plurality of repetitions of a non-magnetic and a magnetic layer. Examples of non-magnetic materials that can be used in spin-torque devices include: Heavy metals: Heavy metals with strong spin-orbit coupling, such as platinum (Pt), tantalum (Ta), and ruthenium (Ru), can be used as spin current sources or spin sink layers in spin-torque devices. These materials efficiently generate or absorb spin currents and facilitate the transfer of angular momentum between the spin and the orbital motion of the electron.

[0023] Insulators: Insulating materials such as aluminum oxide (Al2O3) or magnesium oxide (MgO) can be used as tunnel barriers in magnetic tunnel junctions (MTJs). These insulating layers act as electrical insulators between the magnetic layers while simultaneously allowing spin-dependent tunnel currents. Tunnel barrier properties, such as high resistance and low leakage current, are crucial for device operation.

[0024] Examples of magnetic materials that can be used in spin torque devices include: Ferromagnetic materials: Ferromagnetic materials such as permalloy (NiFe) and cobalt (Co) alloys are used as the magnetic layers in spin-torque devices. These materials possess permanent magnetization and can be manipulated by spin currents. Ferromagnetic layers are often used as the free layer in spin-transfer torque magnetic random access memory (STT-MRAM) or as the reference layer in magnetic tunnel junctions (MTJs).

[0025] Antiferromagnetic materials: Antiferromagnetic materials such as iridium manganese (IrMn) are used as pinning layers in spin-torque devices. These materials exhibit a unique magnetic ordering in which neighboring magnetic moments align antiparallel. The antiferromagnetic pinning layer helps stabilize the magnetization orientation of the free layer and increases the stability of the device.

[0026] The combination of non-magnetic and magnetic materials enables efficient generation, manipulation, and detection of spin currents in spin-torque devices. The specific choice of materials depends on the desired functionality, performance requirements, and compatibility with the device architecture.

[0027] In some embodiments, the layer stack comprises a multilayer comprising a plurality of repetitions of a first non-magnetic layer (e.g., Ta), a magnetic layer (e.g., CoFeB), and a second non-magnetic layer (e.g., MgO).

[0028] In some embodiments, the ferromagnetic layer is magnetized in-plane. The ferromagnetic layer may exhibit permanent magnetization even in the absence of an external magnetic field and may be essential for manipulating the magnetization dynamics through the application of spin currents. In spin-torque devices, a spin current can be injected from a heavy metal layer into an adjacent ferromagnetic layer. The spin current exerts a torque on the magnetization of the ferromagnetic layer, thus enabling control and manipulation of its orientation.

[0029] In some embodiments, the ferromagnetic layer comprises an out-of-plane multi-domain state. In the context of spin torque and spintronics, a multi-domain state refers to the arrangement of magnetic domains within a magnetic layer in a spin-torque device. Spin-torque devices utilize spin currents to control the magnetization dynamics and change the magnetization orientation of the magnetic layer. In a spin-torque device, a magnetic layer typically comprises a ferromagnetic material that has permanent magnetization. However, due to various factors such as the size, shape, and magnetic anisotropy of the magnetic layer, it may be divided into multiple magnetic domains. A multi-domain state in a spin-torque device occurs when the magnetic layer comprises multiple magnetic domains with different magnetization orientations.Each domain represents a region where the magnetization is aligned in a specific direction, but the domains can have distinct boundaries called domain walls. The presence of multiple magnetic domains influences the behavior of spin currents in the device. When a spin current is injected into a multi-domain magnetic layer, it can exert torques on the domain walls and interact with the magnetization within each domain. This interaction can lead to domain wall motion, domain extension or contraction, and changes in the overall magnetization state of the device.

[0030] In some embodiments, the control circuit is configured to inject the currents into the arms of the Hall cross as spin-polarized currents. Spin-polarized currents are electrical currents in which the individual electrons exhibit a preferred spin orientation. In other words, the current carries a net spin polarization, meaning, for example, there is an imbalance between the number of electrons with spin up and spin down.

[0031] According to another aspect, the present disclosure proposes an anomalous Hall detection method. The method comprises applying current(s) through a first arm of a Hall cross extending in a first direction. The first direction may, for example, be referred to as the x-direction. The method comprises measuring voltage(s) across the second arm of the Hall cross in response to the current(s) through the first arm. The method comprises applying current(s) through the second arm of the Hall cross extending in a second direction perpendicular to the first direction. The second direction may, for example, be referred to as the y-direction. The method comprises measuring voltage(s) across the first arm of the Hall cross in response to the current(s) through the second arm.The method further comprises calculating a component of an external magnetic field in a third direction perpendicular to the first and second directions based on a combination of the measured voltages. The third direction may be referred to, for example, as the z-direction. Short description of the characters

[0032] Some examples of devices and / or methods are described below solely by way of example and with reference to the accompanying figures, in which: Fig. 1 illustrates an anomalous Hall sensor according to embodiments of the present disclosure; Fig. 2 shows an example of a layered Hall cross; Fig. 3 illustrates an anomalous Hall sensor according to an embodiment of the present disclosure; Fig. 4 illustrates a flowchart of an abnormal Hall detection method; Fig. Figure 5A illustrates a principle of measuring fields in the plane; Fig. Figure 5B shows a measured external Bx field with an SOT current applied in the x-direction and the anomalous Hall voltage measured in the y-direction. Offset suppression almost completely eliminated the electrical offset, and the linear range is approximately + / -0.5 mT. Fig. Figure 6A illustrates a principle of out-of-plane field measurement; Fig. Figure 6B shows a measured signal of an external Bz field; Fig. Figure 7A shows a measured Bz signal for different bias fields; Fig. Figure 7B shows a measured Bx signal with Bz bias fields of different amplitudes; and Fig. Figure 7C shows a measured Bx signal with By bias fields of different amplitudes. Detailed description

[0033] Some examples will now be described in more detail with reference to the accompanying figures. However, other possible examples are not limited to the features of these detailed embodiments. Other examples may include modifications of the features, as well as equivalents and alternatives to the features. Furthermore, the terminology used herein to describe specific examples is not intended to be limiting of other possible examples.

[0034] Throughout the description of the figures, identical or similar reference numerals refer to identical or similar elements and / or features, which may be implemented identically or in a modified form while providing the same or a similar function. Furthermore, in the figures, the thicknesses of lines, layers, and / or regions may be exaggerated for clarity.

[0035] When two elements A and B are combined using "or," this is to be understood as disclosing all possible combinations, i.e., only A, only B, and A and B, unless explicitly defined otherwise in the individual case. Alternative wording for the same combinations may be "at least one of A and B" or "A and / or B." This applies accordingly to combinations of more than two elements.

[0036] If a singular form is used, such as "a," "an," and "the," and the use of only a single element is neither explicitly nor implicitly defined as mandatory, further examples may also use multiple elements to implement the same function. If a function is subsequently described as being implemented using multiple elements, further examples may implement the same function using a single element or a single processing entity.It is further understood that the terms "comprises", "comprising", "has" and / or "having" when used describe the presence of the specified features, integers, steps, operations, processes, elements, components and / or a group thereof, but do not preclude the presence or addition of one or more other features, integers, steps, operations, processes, elements, components and / or a group thereof.

[0037] Fig. Figure 1 illustrates an anomalous Hall sensor 100 according to embodiments of the present disclosure. The anomalous Hall sensor 100 is a type of magnetic field sensor that utilizes the anomalous Hall effect to detect and measure magnetic fields.

[0038] When a non-ferromagnetic metallic sample is subjected to a perpendicular external magnetic field B, the Lorentz force acting on the current carriers leads to a transverse strain in the plane of the sample. The transverse component of the resistivity, ρ xy , depends on the magnetic field by the relationship ρ xy = R0B, where R0 = 1 / (n e ) is known as the Hall coefficient, n is the carrier density, and -e is the electron charge. This phenomenon, whose explanation is quite classical, is known as the ordinary Hall effect and is understandable. The determination of the Hall coefficient R0 has become the tool of choice for measuring carrier densities in conducting materials.

[0039] It was subsequently discovered that in many ferromagnets, the transverse resistivity includes an additional term independent of the magnetic field, which is often proportional to the magnetization M of the ferromagnetic sample and becomes constant once the sample reaches its saturation magnetization. This effect is called the anomalous Hall effect (A-HE). While the ordinary Hall effect of classical physics requires an external magnetic field, the anomalous Hall effect requires only magnetization, and it was soon realized that ferromagnets exhibit spontaneous Hall conductivity even in the absence of an external magnetic field. The effect has subsequently been observed in a wide variety of systems, including transition metals and their oxides, materials exhibiting colossal magnetoresistance, ferromagnetic semiconductors, topological insulators, and a range of other topological materials.

[0040] The anomalous Hall effect is based on the fact that when a current passes through a magnetic material, electrons are deflected predominantly in one direction. This results in an additional current perpendicular to the driving current, which disappears when the material is non-magnetic. The mechanisms responsible for this deflection have been the subject of considerable controversy since Hall's experimental work. While several mechanisms are known to be responsible, the main players are unified by the spin-orbit interaction—magnetism alone is usually insufficient to induce an anomalous Hall current. Furthermore, spin-orbit coupling effects are usually divided into intrinsic processes, which arise from the band structure of a material, and extrinsic processes, which are related to scattering events.Recent research has shown that intrinsic spin-orbit coupling effects are intertwined with the topological properties of a material's band structure, and that the interplay between intrinsic and extrinsic processes is highly nontrivial. Thus, the physical concepts of ferromagnetism and spin-orbit coupling are at the heart of the anomalous Hall effect.

[0041] The anomalous Hall sensor 100 includes a Hall cross 110. The Hall cross 110 is a specific geometry or layout of a Hall sensor that includes four terminals 112-1 through 112-4 arranged in a cross-like pattern. A first arm 114-1 of the Hall cross 110 connects the terminals 112-1 and 112-2 and extends in a first direction (x-direction). A second arm 114-2 of the Hall cross 110 connects the terminals 112-3 and 112-4 and extends in a second direction (y-direction).

[0042] As in the example of Fig. As shown in Fig. 2, the Hall cross 110 is formed in a layer stack 200 comprising at least one ferromagnetic layer 210 and one or more further layers 220 for spin-orbit coupling. Since the AHE requires magnetization, the ferromagnetic layer 210 can be magnetized in a plane spanned by the first and second directions (e.g., xy-plane). In the example shown in Fig. 2, the magnetization of the ferromagnetic layer 210 runs in the x-direction. A material of the ferromagnetic layer 210 can be, for example, NiFe or CoFeB. Below the ferromagnetic layer 210, the layer stack 200 comprises a heavy metal layer 220 for spin-orbit coupling. A material of the heavy metal layer 220 can be, for example, Pt, Ta, Ru, or Pd.

[0043] A possible structure of the sensitive element is shown in Fig. 2. It is a Hall cross-like structure with a heavy metal layer that converts electric current into a polarized spin current. Above the heavy metal layer is a ferromagnetic layer that is polarized in the plane (xy plane) (in Fig. 2 in the x-direction). As explained above, the Fig. The structure shown in Figure 2 is merely an example. Other layers are also possible. For example, the Hall cross 110 can also have a Ta / CoFeB / MgO heterostructure.

[0044] The anomalous Hall sensor 100 further includes a control circuit 120. The control circuit 120 may include one or more power supply circuits, clock circuits, measurement circuits, etc. The control circuit 120 is configured to apply current(s) through the first arm 114-1 of the Hall cross 110 (via terminals 112-1 and 112-2) and, in response to the current(s) through the first arm 114-1, to generate voltage(s) across the second arm 114-2 of the Hall cross 110 (via terminals 112-3 and 112-4). The control circuit 120 is further configured to apply current(s) through the second arm 114-2 of the Hall cross (via terminals 112-3 and 112-4) and, in response to the current(s) through the second arm 114-2, to generate voltage(s) across the first arm 114-1 of the Hall cross (via terminals 112-1 and 112-2). Thus, the control circuit 120 is configured to apply a spinning current scheme to the Hall cross 110.

[0045] The anomalous Hall sensor 100 further includes a processor 130. The processor 130 may include one or more analog and / or digital signal processing circuits. The processor 130 is configured to determine a component of an external magnetic field in the z-direction based on the measured voltages in response to the spinning current scheme. In particular, the processor 130 may be configured to determine the component of the external magnetic field in the z-direction based on a combination of the measured voltages in response to the spinning current scheme.

[0046] Fig. 3 shows an embodiment of the anomalous Hall sensor 100 and its electronic connections in detail.

[0047] A power supply circuit 122 of the control circuit 120 and the processor 130 are clocked by a clock circuit 124 of the control circuit 120. The power supply circuit 122 is coupled to each of the terminals 112-1 through 112-4 to inject currents into the first arm 114-1 and the second arm 114-2 of the Hall cross 110. The processor 130 is also coupled to each of the terminals 112-1 through 112-4 to measure the resulting (Hall) voltages across the first arm 114-1 and the second arm 114-2 of the Hall cross 110.

[0048] The power supply circuit 122 is configured to apply a first current +Ixx through the first arm 114-1 of the Hall cross 110. The first current +Ixx may be a current from terminal 112-1 to terminal 112-2 in the positive x-direction. The processor 130 is configured to measure a first (Hall) voltage Vxy(+Ixx) across the second arm 114-2 (across terminals 112-3 and 112-4) of the Hall cross 110 in response to the first current +Ixx. The power supply circuit 122 is further configured to apply a second current -Ixx, opposite to the first current +Ixx, through the first arm 114-1 of the Hall cross 110. The second current -Ixx may be a current from terminal 112-2 to terminal 112-1 in the negative x-direction. The processor 130 is configured to measure a second (Hall) voltage Vxy(-Ixx) across the second arm 114-2 (across the terminals 112-3 and 112-4) of the Hall cross 110 in response to the second current -Ixx.The power supply circuit 122 is further configured to apply a third current +Iyy through the second arm 114-2 of the Hall cross 110. The third current +Iyy may be a current from terminal 112-3 to terminal 112-4 in the positive y-direction. The processor 130 is configured to measure a third (Hall) voltage Vyx (+Iyy) across the first arm 114-1 (across terminals 112-1 and 112-2) of the Hall cross 110 in response to the third current +Iyy. The power supply circuit 122 is further configured to apply a fourth current -Iyy, opposite to the third current, through the second arm 114-2 of the Hall cross 110. The fourth current -Iyy may be a current from terminal 112-4 to terminal 112-3 in the negative y-direction. The processor 130 is configured to measure a fourth (Hall) voltage Vyx(-Iyy) across the first arm 114-1 (across the terminals 112-1 and 112-2) of the Hall cross 110 in response to the fourth current -Iyy.

[0049] The power supply circuit 122 provides the Hall cross 110 with current(s). For this purpose, the power supply circuit 122 may include current sources. A resulting signal is measured and analyzed in the signal processing unit 130 and output as a digital or analog signal proportional to each field component (Vx, Vy, Vz). The timing of the supply 122 and the signal processing unit 130 is controlled by the clock 124. The currents ±Ixx and ±Iyy can be applied alternately, and the corresponding Hall voltages Vxy or Vyx can be recorded. The output signal can be calculated, for example, using the formulas in the upper right corner in Fig. 3. The voltage is measured via the anomalous Hall effect on the vertical arms 114-1, 114-2. Depending on the direction in which the electric current is applied (Ixx or Iyy), the anomalous Hall voltage is referred to as Vxy for an Ixx current and as Vyx for an Iyy current (in Fig. 3).

[0050] The component of the external magnetic field in the z-direction can be determined based on a combination of the four voltages Vxy(+Ixx), Vxy(-Ixx), Vyx(+Iyy), and Vyx(-Iyy). The component of the external magnetic field in the z-direction can, for example, be proportional to Vz=(Vyx(+Iyy)−Vyx(−Iyy))−(Vxy(+Ixx)−Vxy(−Ixx)).

[0051] The component of the external magnetic field in the x-direction can be determined based on a combination of the first voltage Vxy(+Ixx) and the second voltage Vxy(-Ixx). The component of the external magnetic field in the x-direction can, for example, be proportional to Vx=Vxy(+Ixx)+Vxy(−Ixx).

[0052] The component of the external magnetic field in the y-direction can be determined based on a combination of the third voltage Vyx(+Iyy) and the fourth voltage Vyx(-Iyy). The component of the external magnetic field in the y-direction can, for example, be proportional to Vy=Vyx(+Iyy)+Vyx(−Iyy).

[0053] The anomalous Hall sensor 100 enables an anomalous Hall detection method 400, the flowchart of which is shown in Fig. 4 is shown.

[0054] The method 400 includes applying 410 current(s) through a first arm of a Hall cross extending in a first direction. The first direction may, for example, be referred to as the x-direction. The method 400 further includes measuring 420 voltage(s) across the second arm of the Hall cross in response to the current(s) through the first arm. The method 400 further includes applying 430 current(s) through the second arm of the Hall cross extending in a second direction perpendicular to the first direction. The second direction may, for example, be referred to as the y-direction. The method 400 further includes measuring 440 voltage(s) across the first arm of the Hall cross in response to the current(s) through the second arm.Furthermore, method 400 includes calculating 450 a component of an external magnetic field in a third direction perpendicular to the first and second directions based on a combination of the measured voltages. The third direction may be referred to, for example, as the z-direction. The measured voltages may also be divided by the respective currents to obtain the respective anomalous Hall resistance.

[0055] The principle of measuring in-plane fields via the spin-orbit torque device is described in Fig. 5A. For measuring an external Bx field, the anomalous Hall voltage V can be measured and the anomalous Hall resistance R can be calculated using the following formula. R=VI where I is the SOT current. To eliminate the device's electrical offset, the sign of the SOT current can be reversed and the anomalous Hall resistances can be subtracted from each other, as in the following formula. Signalx=Vxy+Ixx−Vxy−Ixx where + / -Ixx is the SOT current in + / - x direction.

[0056] The resistance for measuring an external by-field can be calculated using the following formula. Signaly=Vyx+Iyy−Vyx−Iyy where Iyy is the SOT current applied in the y-direction.

[0057] The measured signal of an external Bx field is in Fig. 5B. The sensor response shows almost no offset and a linear range of approximately + / -0.5 mT.

[0058] The spinning current technique is used to measure external fields in the z-direction. This is Fig. 6A. The external Bz field is measured via an SOT current applied in the x and y directions. In both cases, the anomalous Hall voltage is measured.

[0059] The formula for calculating the signal can look like this. SignalZ=(Vyx+Iyy+Vyx−Iyy)−(Vxy+Ixx+Vxy−Ixx)

[0060] The measured signal is in Fig. 6B can be seen.

[0061] The presented detection principle can remain unaffected by bias fields that are in the linear range of the detection device (+ / -0.5 mT). Fig. Figure 7A shows the measured Bz signal with different amplitudes for Bx bias fields. For higher bias field amplitudes (+ / -0.5 mT), the linear range decreases in the detection direction. The sensor's sensitivity and offset are unaffected by bias fields and remain virtually unchanged.

[0062] In Fig. Figure 7B shows the measured Bx signal with Bz bias fields. For bias fields within the linear range, the sensitivity and offset are unaffected. However, for stronger bias fields, the sensitivity decreases, which is evident in the measurement data with a Bz bias field of 1 mT.

[0063] In Fig. Figure 7C shows the measured Bx signal with different By bias fields. Again, the offset and sensitivity are unaffected by bias fields within the sensor's linear range. At the higher bias field of 1 mT, the reduction in sensitivity is again visible.

[0064] This enables the design of a single-component 3D magnetic field sensor based on SOT without cross-sensitivities and active offset compensation.

[0065] According to the present disclosure, the anomalous Hall sensor 100 uses a single domain layer, which can lead to more reliable performance since it is not necessary to create the domain wall prior to use. Known 3D sensors do not use the spinning current technique for the z-axis and are therefore unable to compensate for offsets in this direction. According to the present disclosure, the spinning current technique is used in the z-direction and the SOT effect is used for the xy field components, resulting in very low offset in all directions.

[0066] According to the present disclosure, the magnetization is switched in basically opposite directions by the SOT current.

[0067] According to the present disclosure, a spinning current concept is used for anomalous Hall sensors. In particular, a single device is proposed that can be used to measure magnetic fields in all three directions and compensate for the respective offsets. The device uses spin-orbit torque (SOT) to rotate the magnetization of a ferromagnetic layer in the sensitive direction of the sensor, which is measured using the anomalous Hall effect (or alternatively, another technique sensitive to out-of-plane fields, such as TMR with an out-of-plane reference layer). To suppress offsets, the spinning current technique is used, in which the SOT current direction is reversed.

[0068] By flipping the SOT current, the offset can be compensated, but only for the xy field measurements. This does not work for the Bz field measurements with only one component. This can be solved by combining the x and y measurements in such a way that the SOT and offset contributions in the signal are suppressed. Thus, the field in all three directions can be obtained from the four measurements with active offset compensation.

[0069] Some advantages are: Offset reduction - No cross-sensitivity in other field directions - Linear range can be tuned by current - A free layer in the plane can be used to detect fields outside the plane. - A sensor can be used to detect x, y and z field components.

[0070] The aspects and features described in connection with a particular one of the previous examples may also be combined with one or more of the further examples to replace an identical or similar feature of that further example or to additionally introduce the feature into the further example.

[0071] It is further understood that the disclosure of multiple steps, processes, operations, or functions disclosed in the specification or claims should not be construed as necessarily being in the described order, unless explicitly stated in the individual case or absolutely necessary for technical reasons. Therefore, the foregoing description does not limit the performance of multiple steps or functions to any particular order. Furthermore, in further examples, a single step, function, process, or operation may include and / or be broken down into multiple sub-steps, functions, processes, or operations.

[0072] If some aspects are described in connection with a component or system, these aspects are also to be understood as a description of the corresponding method. For example, a block, a component, or a functional aspect of the component or system can correspond to a feature, such as a method step, of the corresponding method. Accordingly, aspects described in connection with a method are also to be understood as a description of a corresponding block, a corresponding element, a property, or a functional feature of a corresponding component or system.

[0073] The following claims are hereby incorporated into the Detailed Description, and each claim may stand on its own as a separate example. It should also be noted that although a dependent claim in the claims refers to a particular combination with one or more other claims, other examples may include a combination of the dependent claim with the subject matter of any other dependent or independent claim. Such combinations are hereby explicitly contemplated unless it is specifically stated that a particular combination is not intended. Furthermore, features of a claim for any other independent claim are also intended to be encompassed, even if that claim is not directly defined as dependent on that other independent claim.

Claims

[1] An anomalous Hall sensor (100) comprising a Hall Cross (110), comprising a layer stack (200) with a ferromagnetic layer (210), a first arm (114-1) of the Hall cross formed in the layer stack and extends in a first direction, and a second arm (114-2) of the Hall cross, which is formed in the layer stack and extends in a second direction perpendicular to the first direction; a control circuit (120) which is designed applying current through the first arm (114-1) of the Hall cross and measuring voltage across the second arm (114-2) of the Hall cross in response to the current through the first arm, applying current through the second arm (114-2) of the Hall cross and measuring voltage across the first arm (114-1) of the Hall cross in response to the current through the second arm; and a processor (130) configured to: calculate a component of an external magnetic field in a third direction perpendicular to the first and second directions based on a combination of the measured voltages. [2] The abnormal Hall sensor (100) according to claim 1, wherein the control circuit (120) is formed, applying a first and a second current through the first arm (114-1) of the Hall cross in opposite directions and measuring a respective first and second voltage across the second arm (114-2) of the Hall cross in response to the respective currents, applying a third and a fourth current through the second arm (114-2) of the Hall cross in opposite directions and measuring a respective third and fourth voltage across the first arm (114-1) of the Hall cross in response to the respective currents, and the processor (130) is configured to calculate the component of the external magnetic field in the third direction based on a combination of the measured four voltages. [3] The anomalous Hall sensor (100) according to claim 2, wherein the processor (130) is configured to calculate a component of the external magnetic field in the first direction based on a combination of the measured first and second voltages. [4] The anomalous Hall sensor (100) according to claim 3, wherein the processor (130) is configured to calculate the component of the external magnetic field in the first direction based on a sum of the measured first and second voltages. [5] The anomalous Hall sensor (100) according to any one of claims 2 to 4, wherein the processor (130) is configured to calculate a component of the external magnetic field in the second direction based on a combination of the measured third and fourth voltages. [6] The anomalous Hall sensor (100) according to claim 5, wherein the processor (130) is configured to calculate the component of the external magnetic field in the second direction based on a sum of the measured third and fourth voltages. [7] The anomalous Hall sensor (100) according to any one of claims 2 to 6, wherein the combination of the measured four voltages comprises a first difference of the third and fourth voltages and a second difference of the first and second voltages. [8] The anomalous Hall sensor (100) according to claim 7, wherein the combination of the measured four voltages corresponds to a difference between the second difference and the first difference. [9] The anomalous Hall sensor (100) according to any one of the preceding claims, wherein the layer stack (200) comprises at least one conductive non-magnetic layer (220) and the ferromagnetic layer (210). [10] The anomalous Hall sensor (100) according to claim 9, wherein the conductive non-magnetic layer (220) comprises a heavy metal layer. [11] The anomalous Hall sensor (100) according to any one of the preceding claims, wherein the layer stack comprises a multilayer comprising a plurality of repetitions of a non-magnetic and a magnetic layer. [12] The anomalous Hall sensor (100) according to any one of the preceding claims, wherein the layer stack (200) comprises a multilayer comprising a plurality of repetitions of a first non-magnetic layer (220), a magnetic layer (210) and a second non-magnetic layer. [13] The anomalous Hall sensor (100) according to claim 11 or 12, wherein at least one non-magnetic layer is a heavy metal layer. [14] The anomalous Hall sensor (100) according to any one of the preceding claims, wherein the control circuit (120) is configured to inject the currents into the arms of the Hall cross (110) respectively as spin-polarized currents. [15] An anomalous Hall detection method (400) comprising applying (410) a current through a first arm of a Hall cross extending in a first direction; measuring (420) a voltage across the second arm of the Hall cross in response to the current through the first arm; applying (430) a current through the second arm of the Hall cross extending in a second direction perpendicular to the first direction; Measuring (440) the voltage across the first arm of the Hall cross in response to the current through the second arm; and Calculating (450) a component of an external magnetic field in a third direction perpendicular to the first and second directions based on a combination of the measured voltages.

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