Abnormal Hall sensor and abnormal Hall sensing method

Abstract

The invention relates to an anomalous Hall sensor and an anomalous Hall sensing method. The present disclosure relates to an anomalous Hall sensor including a Hall cross. The Hall cross includes a stack of layers, the stack of layers including ferromagnetic layers. A first arm of the Hall cross formed in the layer stack extends in a first direction. A second arm of the Hall cross formed in the layer stack extends in a second direction perpendicular to the first direction. The anomalous Hall sensor includes a control circuit configured to: apply a current through a first arm of the Hall cross, and measure a voltage across a second arm of the Hall cross in response to the current through the first arm; a current through the second arm of the Hall cross is applied, and a voltage across the first arm of the Hall cross is measured in response to the current through the second arm. The anomalous Hall sensor also includes a processor configured to calculate a component of the external magnetic field in a third direction perpendicular to the first direction and the second direction based on a combination of the measured voltages.

Description

Technical Field

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

[0002] In magnetic field sensors, a small offset can be critical to fully exploit the signal-to-noise ratio and reduce unwanted environmental dependencies. This is especially true for the measurement of small signals, such as the earth's magnetic field in compass applications or high-precision 3D magnetic sensing. Offset compensation techniques are well established for Hall-based devices, but are lacking for magnetoresistive devices, which typically offer a higher signal-to-noise ratio. In addition, in order to be able to measure the field in all three directions (x, y, z), separate dedicated devices are usually used for each direction, which increases the complexity of development and manufacturing as well as the size of the sensing circuit device.

[0003] In conventional 3D Hall sensors, three different sensitive elements are required to detect fields in all three directions. These sensors have a limited signal-to-noise ratio, but active offset compensation can be achieved via spin current technology. Using spin-orbit torque (SOT), the concept of a 3D magnetic field sensor with a single sensitive element has been proposed in Nature Electronics 4.3 (2021): 179-184 by Li, Ruofan et al., “A spin–orbit torque device for sensing three-dimensional magnetic fields.” However, in this case, the domain walls employed may lead to noise and irreproducible behavior. When the domain walls are annihilated from the sensor due to a larger external magnetic field, the sensor response may change or even its functional behavior may be destroyed.

[0004] SOT can manifest in a variety of systems involving magnetic materials and structures. When an electric current passes through a heavy metal or a layered structure composed of different materials, the spin-orbit interaction, or coupling, can generate a torque on the magnetization of adjacent magnetic layers.

[0005] In the conventional Hall effect, when a current flows through a conductive material placed in a magnetic field perpendicular to the current, a transverse voltage, the Hall voltage, is induced on the material. This voltage is proportional to the product of the applied current, the magnetic field strength, and a material-related 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 is generated due to the anomalous Hall effect (AHE). The AHE is related to the spin-related scattering of charge carriers within the material. It causes an asymmetry in the charge carrier trajectory, resulting in the deflection of the carriers and the appearance of an additional Hall voltage perpendicular to the applied current and magnetic field.

[0006] Therefore, it may be desirable to use AHE to improve spin-orbit torque devices or anomalous Hall sensors. Summary of the invention

[0007] The apparatus and method according to the present invention solves this need.The following provides potentially advantageous embodiments.

[0008] According to a first aspect, the present disclosure proposes an abnormal Hall sensor using an AHE. The abnormal Hall sensor includes a Hall cross. The Hall cross includes a layer stack, which includes at least one ferromagnetic layer next to at least one other layer. The layer stack may have several possible embodiments. The first arm of the Hall cross formed in the layer stack extends in a first direction. For example, the first direction can be referred to as the x direction. The second arm of the Hall cross formed in the layer stack extends in a second direction perpendicular to the first direction. For example, the second direction can be referred to as the y direction. The abnormal Hall sensor also includes a control circuit configured to apply (multiple) currents through the first arm of the Hall cross, and measure (multiple) voltages at both ends of the second arm of the Hall cross in response to (multiple) currents through the first arm. The control circuit is also configured to apply (multiple) currents through the second arm of the Hall cross, and measure (multiple) voltages at both ends of the first arm of the Hall cross in response to (multiple) currents through the second arm. The abnormal Hall sensor also includes a processor configured to calculate a component of an external magnetic field in a third direction perpendicular to the first direction and the second direction based on a combination of the measured voltages. For example, the third direction may be referred to as the z-direction.

[0009] Therefore, the present disclosure proposes a spin current technique for an anomalous Hall sensor. By applying corresponding currents to the two arms of the Hall cross, the component of the external magnetic field in a third direction perpendicular to the first direction and the second direction can be determined.

[0010] The Hall cross may include a (e.g., rectangular, square, or cross-shaped) layered structure having four electrical contacts arranged in a cross-like pattern. A first arm of the Hall cross interconnects two of the four contacts in a first direction (e.g., x-direction), and a second arm of the Hall cross interconnects another two of the four contacts in a second direction (e.g., y-direction).

[0011] In some embodiments, the control circuit is configured to apply a first current and a second current through the first arm of the Hall cross in opposite directions, and measure the corresponding first voltage and second voltage at both ends of the second arm of the Hall cross in response to the corresponding current. If the first direction is the x direction, the first current and the second current may be currents in the positive x direction and the negative x direction. The control circuit may also be configured to apply a third current and a fourth current through the second arm of the Hall cross in opposite directions, and measure the corresponding third voltage and fourth voltage at both ends of the first arm of the Hall cross in response to the corresponding current. If the second direction is the y direction, the third current and the fourth current may be currents in the positive y direction and the 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 the combination of the four measured voltages. For example, the combination of the four measured voltages may include a first difference between the third voltage and the fourth voltage and a second difference between the first voltage and the second voltage. In a particular embodiment, the combination of the four measured voltages may correspond to the difference between the second difference and the first difference.

[0012] In some embodiments, the processor is further configured to calculate a component of the external magnetic field in a first direction (e.g., x-direction) based on a combination of the first voltage and the second voltage measured in response to the corresponding current. For example, the processor can be configured to calculate a component of the external magnetic field in a first direction (e.g., x-direction) based on the sum of the measured first voltage and the second voltage.

[0013] In some embodiments, the processor is further configured to calculate a component of the external magnetic field in a second direction (e.g., y direction) based on a combination of the third voltage and the fourth voltage measured in response to the corresponding current. For example, the processor can be configured to calculate a component of the external magnetic field in a second direction (e.g., y direction) based on the sum of the measured third voltage and the fourth voltage.

[0014] Therefore, a 3D anomalous Hall sensor can be obtained.

[0015] In some embodiments, the layer stack includes at least one conductive non-magnetic layer and a ferromagnetic layer formed on top of each other. For example, the conductive non-magnetic layer may include a heavy metal layer. Some examples of heavy metals that may be used in spin torque devices include:

[0016] Platinum (Pt): Platinum is a heavy metal widely used in spin electronics 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 spin electronic 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 current.

[0018] Ruthenium (Ru): Ruthenium is a heavy metal that provides good spin-orbit coupling and is used in spintronic devices, especially in magnetic tunnel junctions (MTJs) and spin transfer torque devices.

[0019] Palladium (Pd): Although not as commonly used as platinum, palladium is another heavy metal that can generate spin currents due to its strong spin-orbit coupling. It has been studied for its potential in spintronic applications.

[0020] Some examples of ferromagnetic materials that can be used in spin-torque devices include:

[0021] Permalloy (NiFe): Permalloy is a ferromagnetic alloy of nickel and iron that 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 a free layer or reference layer in spin transfer torque magnetic random access memory (STT-MRAM) and magnetic tunnel junction (MTJ).

[0022] Cobalt (Co) and cobalt alloys: Cobalt and its alloys, such as CoFeB (cobalt-iron-boron), can be used in spin torque devices. They have strong magnetic anisotropy and are often used as reference layers in STT-MRAM and magnetic sensors.

[0023] Rare earth transition metal alloys: Certain rare earth transition metal alloys, such as gadolinium iron garnet (GdIG), have been investigated for use in spin torque devices. These materials exhibit interesting magnetic and spin electronic properties that may be advantageous for specific applications.

[0024] In a spin-torque device, 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, allowing its orientation to be controlled and manipulated.

[0025] In some embodiments, the layer stack includes multiple layers consisting of multiple repetitions of non-magnetic layers and magnetic layers. Examples of non-magnetic materials that can be used for spin torque devices include:

[0026] 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 sinks in spin-torque devices. These materials efficiently generate or absorb spin currents and facilitate the transfer of angular momentum between electron spins and orbital motion.

[0027] 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 magnetic layers while allowing spin-dependent tunneling currents. Tunnel barrier properties such as high resistance and low leakage current are critical to the operation of the device.

[0028] Examples of magnetic materials that can be used in spin-torque devices include:

[0029] Ferromagnetic materials: Ferromagnetic materials, such as Permalloy (NiFe) and cobalt (Co) alloys, are used as magnetic layers in spin torque devices. These materials have permanent magnetization and can be manipulated by spin current. Ferromagnetic layers are often used as free layers in spin transfer torque magnetic random access memory (STT-MRAM) or as reference layers in magnetic tunnel junctions (MTJs).

[0030] Antiferromagnetic materials: Antiferromagnetic materials, such as iridium manganese (IrMn), are used as pinning layers in spin-torque devices. These materials exhibit a unique magnetic order in which adjacent magnetic moments are aligned antiparallel. The antiferromagnetic pinning layer helps stabilize the magnetization orientation of the free layer and enhances the stability of the device.

[0031] The combination of nonmagnetic and magnetic materials allows for 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.

[0032] In some embodiments, the layer stack includes a multilayer consisting of multiple repetitions of a first nonmagnetic layer (eg, Ta), a magnetic layer (eg, CoFeB), and a second nonmagnetic layer (eg, MgO).

[0033] In some embodiments, the ferromagnetic layer is magnetized in-plane. Ferromagnetic layers can exhibit permanent magnetization even in the absence of an external magnetic field and are essential for manipulating the magnetization dynamics by applying a spin current. In a spin torque device, 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, allowing its orientation to be controlled and manipulated.

[0034] In some embodiments, the ferromagnetic layer includes an out-of-plane multi-domain state. In the context of spin torque and spin electronics, the multi-domain state refers to the arrangement of magnetic domains within a magnetic layer in a spin torque device. Spin torque devices use spin currents to control the magnetization dynamics and switch the magnetization orientation of the magnetic layer. In a spin torque device, the magnetic layer is typically composed of a ferromagnetic material that exhibits permanent magnetization. However, due to various factors such as the size, shape, and magnetic anisotropy of the magnetic layer, it can be divided into multiple magnetic domains. When the magnetic layer includes multiple magnetic domains with different magnetization orientations, a multi-domain state occurs in a spin torque device. Each domain represents a region where the magnetization is aligned in a specific direction, but the domains can have different boundaries called domain walls. The presence of multiple magnetic domains affects the behavior of the spin current in the device. When a spin current is injected into a multi-domain magnetic layer, it can exert a torque on the domain wall and interact with the magnetization within each domain. This interaction can cause domain wall motion, domain expansion or contraction, and changes in the overall magnetization state of the device.

[0035] In some embodiments, the control circuit is configured to inject current into the arms of the Hall cross respectively as spin-polarized current. Spin-polarized current refers to current in which individual electrons have a preferred spin orientation. In other words, the current carries a net spin polarization, which means that there is an imbalance between the number of electrons with spin up and the number of electrons with spin down.

[0036] According to another aspect, the present disclosure proposes an abnormal Hall sensing method. The method includes applying (multiple) currents through a first arm of a Hall cross, the first arm extending in a first direction. For example, the first direction may be referred to as the x-direction. The method includes measuring (multiple) voltages at both ends of a second arm of the Hall cross in response to (multiple) currents through the first arm. The method includes applying (multiple) currents through a second arm of the Hall cross, the second arm extending in a second direction perpendicular to the first direction. For example, the second direction may be referred to as the y-direction. The method includes measuring (multiple) voltages at both ends of the first arm of the Hall cross in response to (multiple) currents through the second arm. In addition, the method includes calculating the component of the external magnetic field in a third direction perpendicular to the first direction and the second direction based on a combination of the measured voltages. For example, the third direction may be referred to as the z-direction. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Some examples of apparatus and / or methods will be described below, by way of example only, and with reference to the accompanying drawings, in which

[0038] Figure 1 An abnormal Hall sensor according to an embodiment of the present disclosure is illustrated;

[0039] Figure 2 An example of a layered Hall cross is illustrated;

[0040] Figure 3 An abnormal Hall sensor according to one embodiment of the present disclosure is illustrated;

[0041] Figure 4 A flow chart of an anomalous Hall sensing method is illustrated;

[0042] Figure 5A The diagram shows the principle of measuring the field in a plane;

[0043] Figure 5B The measured external Bx field with applied SOT current in the x-direction and measured anomalous Hall voltage in the y-direction is shown. Offset cancellation removes almost all electrical offsets and the linear range is approximately + / -0.5mT;

[0044] Fig. 6A The diagram shows the principle of measuring the out-of-plane field;

[0045] Figure 6B shows the measured signal of the external Bz field;

[0046] Fig. 7A shows the Bz signal measured for different bias locations;

[0047] Figure 7B shows the measured Bx signal with various amplitudes of the Bz bias field; and

[0048] Figure 7C The measured Bx signal with various amplitudes of the By bias field is shown. DETAILED DESCRIPTION

[0049] Some examples are now described in more detail with reference to the accompanying drawings. However, other possible examples are not limited to the features of these embodiments described in detail. Other examples may include modifications of features and equivalents and substitutes of features. In addition, the terms used herein to describe certain examples should not limit other possible examples.

[0050] Throughout the description of the drawings, the same or similar reference numerals refer to the same or similar elements and / or features, which may be identical or implemented in a modified form while providing the same or similar functions. For clarity, the thickness of the lines, layers and / or regions in the drawings may also be exaggerated.

[0051] When two elements A and B are combined using "or", this should be understood to disclose all possible combinations, i.e. only A, only B, and A and B, unless otherwise explicitly defined in individual cases. As alternative wording for the same combination, "at least one of A and B" or "A and / or B" can be used. This is equally applicable to combinations of more than two elements.

[0052] If singular forms such as "a", "an", and "the" are used, and there is no explicit or implicit definition that the use of only a single element is mandatory, additional examples may also use several elements to achieve the same function. If a function is described below as being implemented using multiple elements, additional examples may use a single element or a single processing entity to achieve the same function. It should also be understood that the terms "comprise", "comprising", "including", and / or "comprising" when used describe the presence of specified features, wholes, steps, operations, processes, elements, components, and / or groups thereof, but do not exclude the presence or addition of one or more other features, wholes, steps, operations, processes, elements, components, and / or groups thereof.

[0053] Figure 1 An abnormal Hall sensor 100 according to an embodiment of the present disclosure is illustrated. The abnormal Hall sensor 100 is a magnetic field sensor that detects and measures a magnetic field using the abnormal Hall effect.

[0054] When a non-ferromagnetic metal sample is exposed to a perpendicular external magnetic field B, the Lorentz force acting on the current carriers generates a transverse voltage in the plane of the sample. The transverse component of the resistivity ρ xy Through the relationship xy = R0B and depends on the magnetic field, where R0 = 1 / (ne) is called the Hall coefficient, n is the carrier density, and -e is the electron charge. This phenomenon, whose explanation is entirely classical, is called the ordinary Hall effect and is well understood. Determining the Hall coefficient R0 has become the tool of choice for measuring carrier density in conductive materials.

[0055] It was then noticed that in many ferromagnets, the transverse resistivity obtained an additional term independent of the magnetic field, which was often proportional to the magnetization M of the ferromagnetic sample and became a constant once the sample reached its saturation magnetization. This effect is called the anomalous Hall effect (AHE). The ordinary Hall effect of classical physics requires an external magnetic field, while the anomalous Hall effect only requires magnetization, and it was soon realized that ferromagnets exhibit spontaneous Hall conductivity in the absence of an external magnetic field. The effect was subsequently observed in many systems including transition metals and their oxides, in materials exhibiting colossal magnetoresistance, ferromagnetic semiconductors, topological insulators, and many other topological materials.

[0056] The anomalous Hall effect stems from the fact that when an electric current passes through a magnetic material, electrons are deflected primarily in one direction. This results in an additional current perpendicular to the driving current, which vanishes if the material is nonmagnetic. The mechanism that causes this deflection has been the subject of substantial controversy since Hall's experimental work. Several mechanisms are known to work, and the main players are united by spin-orbit interaction - the magnetic force itself is usually not enough to produce an anomalous Hall current. In addition, the spin-orbit coupling effect is conventionally divided into intrinsic processes originating from the band structure of the material and extrinsic processes associated with scattering events. Recent studies have shown that the intrinsic spin-orbit coupling effect is intertwined with the topological properties of the material band structure, and the interaction between the intrinsic and extrinsic processes is very important. Therefore, the core of the anomalous Hall effect lies in the physical concepts of ferromagnetism and spin-orbit coupling.

[0057] The anomalous Hall sensor 100 includes a Hall cross 110. The Hall cross 110 is a specific geometry or layout of the Hall sensor, which includes four terminals 112-1 to 112-4 arranged in a cross-like pattern. The first arm 114-1 of the Hall cross 110 interconnects the terminals 112-1 and 112-2 and extends in a first direction (x direction). The second arm 114-2 of the Hall cross 110 interconnects the terminals 112-3 and 112-4 and extends in a second direction (y direction).

[0058] like Figure 2 As shown in the example of FIG. 1 , the Hall cross 110 is formed in a layer stack 200, which includes at least one ferromagnetic layer 210 and one or more additional layers 220 for spin-orbit coupling. When the AHE requires magnetization, the ferromagnetic layer 210 can be magnetized in a plane spanned by a first direction and a second direction (e.g., an xy plane). Figure 2 In the example shown, the magnetization of the ferromagnetic layer 210 is in the x-direction. For example, the material of the ferromagnetic layer 210 may be NiFe or CoFeB. Below the ferromagnetic layer 210, the layer stack 200 includes a heavy metal layer 220 for spin-orbit coupling. For example, the material of the heavy metal layer 220 may be Pt, Ta, Ru, or Pd.

[0059] Possible structures of sensitive elements are as follows: Figure 2 It is a Hall cross-like structure with a heavy metal layer that converts the current into a spin-polarized current. On top of the heavy metal layer is a ferromagnetic layer that is polarized in the plane (xy plane) (in Figure 2 As mentioned above, Figure 2 The structure shown is only an example. Other layers are also possible. For example, the Hall cross 110 may also include a Ta / CoFeB / MgO heterostructure.

[0060] The anomalous Hall sensor 100 also includes a control circuit 120. The control circuit 120 may include one or more power circuits, clock circuits, measurement circuits, etc. The control circuit 120 is configured to apply (multiple) currents through the first arm 114-1 of the Hall cross 110 (via terminals 112-1 and 112-2), and induce (multiple) voltages across the second arm 114-2 of the Hall cross 110 (via terminals 112-3 and 112-4) in response to the (multiple) currents through the first arm 114-1. The control circuit 120 is also configured to apply (multiple) currents through the second arm 114-2 of the Hall cross (via terminals 112-3 and 112-4), and induce (multiple) voltages across the first arm 114-1 of the Hall cross (via terminals 112-1 and 112-2) in response to the (multiple) currents through the second arm 114-2. Therefore, the control circuit 120 is configured to apply a spinning current scheme to the Hall cross 110.

[0061] The anomalous Hall sensor 100 also includes a processor 130. The processor 130 may include one or more analog signal processing circuits and / or digital signal processing circuits. The processor 130 is configured to determine the component of the external magnetic field in the z direction based on the voltage measured 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 the combination of voltages measured in response to the spinning current scheme.

[0062] Figure 3 An embodiment of an anomalous Hall sensor 100 and its electronic connections are shown in more detail.

[0063] The power supply circuit 122 of the control circuit 120 and the processor 130 are clocked by the clock circuit 124 of the control circuit 120. The power supply circuit 122 is coupled to each of the terminals 112-1 to 112-4 for injecting current 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 to 112-4 for measuring the resulting (Hall) voltage across the first arm 114-1 and the second arm 114-2 of the Hall cross 110.

[0064] 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 the terminal 112-1 to the 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 of the Hall sensor 110 (across the terminals 112-3 and 112-4) in response to the first current +Ixx. The power supply circuit 122 is also configured to apply a second current -Ixx through the first arm 114-1 of the Hall cross 110, which is opposite to the first current +Ixx. The second current -Ixx may be a current from the terminal 112-2 to the 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 of the Hall sensor 110 (across the terminals 112-3 and 112-4) in response to the second current -Ixx. The power supply circuit 122 is also configured to apply a third current +Iyy through the second arm 114-2 of the Hall cross 110. The third current +Iyy can be a current from the terminal 112-3 to the 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 of the Hall cross 110 (across the terminals 112-1 and 112-2) in response to the third current +Iyy. The power supply circuit 122 is also configured to apply a fourth current -Iyy through the second arm 114-2 of the Hall cross 110, which is opposite to the third current. The fourth current -Iyy can be a current from the terminal 112-4 to the 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 of the Hall sensor 110 (across the terminals 112 - 1 and 112 - 2 ) in response to the fourth current -Iyy.

[0065] The power supply circuit 122 provides (multiple) currents to the Hall cross 110. For this purpose, the power supply circuit 122 can include a current source. The resulting signal is measured and analyzed in the signal processing unit 130 and is given as a digital signal or an analog signal proportional to each field component (Vx, Vy, Vz). The time control of the power supply 122 and the signal processing unit 130 is done via the clock 124. The currents ±Ixx and ±Iyy can be applied alternately and the corresponding Hall voltages Vxy or Vyx can be recorded. For example, the output signal can be obtained using Figure 3 The voltage is measured via the anomalous Hall effect at the vertical arms 114-1, 114-2. Depending on the direction of the applied current (Ixx or Iyy), the anomalous Hall voltage is referred to as Vxy for Ixx current and Vyx for Iyy current (in Figure 3 (visualization in ).

[0066] The component of the external magnetic field in the z direction can be determined based on a combination of four voltages Vxy (+Ixx), Vxy (-Ixx), Vyx (+Iyy), and Vyx (-Iyy). For example, the component of the external magnetic field in the z direction can be proportional to the following equation:

[0067] Vz=(Vyx(+Iyy)-Vyx(-Iyy))–(Vxy(+Ixx)-Vxy(-Ixx))

[0068] The component of the external magnetic field in the x-direction may be determined based on a combination of the first voltage Vxy (+Ixx) and the second voltage Vxy (-Ixx). For example, the component of the external magnetic field in the x-direction may be proportional to the following equation:

[0069] Vx=Vxy(+Ixx)+Vxy(-Ixx)

[0070] The component of the external magnetic field in the y direction can be determined based on the combination of the third voltage Vyx (+Iyy) and the fourth voltage Vyx (-Iyy). For example, the component of the external magnetic field in the y direction can be proportional to the following equation:

[0071] Vy=Vyx(+Iyy)+Vyx(-Iyy)

[0072] The abnormal Hall sensor 100 enables the abnormal Hall sensing method 400, the flow chart of which is shown in FIG. Figure 4 shown.

[0073] The method 400 includes applying 410 (multiple) currents through a first arm of a Hall cross, the first arm extending in a first direction. For example, the first direction may be referred to as the x-direction. The method 400 also includes measuring 420 (multiple) voltages across a second arm of the Hall cross in response to the (multiple) currents through the first arm. The method 400 also includes applying 430 (multiple) currents through a second arm of the Hall cross, the second arm extending in a second direction perpendicular to the first direction. For example, the second direction may be referred to as the y-direction. The method 400 also includes measuring 440 (multiple) voltages across the first arm of the Hall cross in response to the (multiple) currents through the second arm. In addition, the method 400 includes calculating 450 a component of an external magnetic field in a third direction perpendicular to the first direction and the second direction based on a combination of the measured voltages. For example, the third direction may be referred to as the z-direction. The measured voltage may also be divided by the corresponding current to obtain a corresponding anomalous Hall resistance.

[0074] The principle of measuring in-plane fields via spin-orbit torque devices is as follows Figure 5AFor the measurement of the external Bx field, the anomalous Hall voltage V can be measured, and the anomalous Hall resistance R can be calculated using the following formula.

[0075]

[0076] Where I is the SOT current. To remove the electrical offset of the device, the sign of the SOT current can be switched and the anomalous Hall resistance can be subtracted from each other, as shown in the following formula.

[0077]

[0078] Where + / -Ixx is the SOT current in the + / -x direction.

[0079] The resistance used for measuring the external By field can be calculated as follows.

[0080]

[0081] where Iyy is the SOT current applied in the y direction.

[0082] The measured signal of the external Bx field is Figure 5B The response of the sensor shows almost no offset and a linear range of approximately + / - 0.5mT.

[0083] For the measurement of the external field in the z direction, the spin current technique was used. Fig. 6A The external Bz field is measured via SOT currents applied in the x-direction and the y-direction. In both cases, the anomalous Hall voltage is measured.

[0084] The formula used to calculate the signal can be shown as follows.

[0085]

[0086] The measured signal is Figure 6B Visualization.

[0087] The presented sensing principle can remain unaffected by bias fields within the linear range (+ / - 0.5 mT) of the sensing device. Fig. 7A In Figure 1, the Bz signal with different amplitudes measured for a Bx bias field is visualized. For higher bias field amplitudes (+ / - 0.5mT), the linear range in the sensing direction decreases. The sensitivity and offset of the sensor are not affected by the bias field and remain almost unchanged.

[0088] exist Figure 7BIn Figure 1, the measured Bx signal with a Bz bias field is visualized. For bias fields in the linear range, the sensitivity and offset are not affected. However, for stronger bias fields, the sensitivity becomes lower, which is visible for the measured data with a Bz bias field of 1 mT.

[0089] exist Figure 7C In Figure 1, the measured Bx signal with different By bias fields is visualized. Again, the offset and sensitivity are not affected by the bias field within the linear range of the sensor. For the higher bias field of 1 mT, a decrease in sensitivity is also visible.

[0090] Thus, the design of a single-device 3D magnetic field sensor based on SOT without cross-sensitivity and active offset compensation is possible.

[0091] According to the present disclosure, the anomalous Hall sensor 100 uses a single domain layer, which can lead to more reliable functional behavior because domain walls do not have to be generated before use. Known 3D sensors do not use spin current technology for the z-axis and therefore cannot eliminate offsets in this direction. According to the present disclosure, spin current technology is used for the z-direction and the SOT effect is used for the xy field components, resulting in very small offsets in all directions. According to the present disclosure, the magnetization is switched in substantially opposite directions due to the SOT current.

[0092] According to the present disclosure, the spin current concept is used for an anomalous Hall sensor. In particular, a single device is proposed that can be used to measure magnetic fields in all three directions and compensate for the corresponding offsets. The device uses spin-orbit torque (SOT) to rotate the magnetization of the ferromagnetic layer to the sensitive direction of the sensor, which can be 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 eliminate the offset, a spin current technique is used, in which the SOT current direction is reversed.

[0093] With the flipping of the SOT current, the offset can be compensated, but only in the xy field measurement. For the Bz field measurement, this does not work for only one device. This can be solved by combining the measurement in the x direction and the measurement in the y direction in a way that the SOT and offset contributions in the signal are eliminated. Thus, from four measurements, the fields in all three directions can be obtained with active offset compensation. Some advantages are:

[0094] -Drift reduction;

[0095] - No cross sensitivity in other field directions;

[0096] -The linear range can be tuned by current intensity;

[0097] - In-plane free layers can be used to detect out-of-plane fields;

[0098] -One sensor device can be used to detect the x-field component, the y-field component and the z-field component.

[0099] The aspects and features described with respect to a specific one of the previous examples may also be combined with one or more other examples to replace the completely identical or similar features of the other examples or to additionally introduce these features into the other examples.

[0100] It should also be understood that the disclosure of several steps, processes, operations or functions disclosed in the specification or claims should not be interpreted as implying that these operations must rely on the described order, unless explicitly stated in individual cases or necessary for technical reasons. Therefore, the previous description does not limit the execution of several steps or functions to a certain order. In addition, in other examples, a single step, function, process or operation can include and / or be decomposed into several sub-steps, sub-functions, sub-processes or sub-operations.

[0101] If some aspects have been described with respect to a device or system, these aspects should also be understood as descriptions of corresponding methods. For example, a block, a device, or functional aspects of a device or system may correspond to features of a corresponding method, such as method steps. Therefore, aspects described with respect to a method should also be understood as descriptions of characteristics or functional features of a corresponding block, corresponding element, corresponding device, or corresponding system.

[0102] The following claims are hereby incorporated into the Detailed Description, where each claim may stand on its own as a separate example. It should also be noted that, although in the claims a dependent claim refers to a specific combination with one or more other claims, other examples may also include a combination of a dependent claim with the subject matter of any other dependent or independent claim. Such combinations are expressly proposed herein, unless it is stated in individual cases that a specific combination is not intended. In addition, features of a claim should also be included in any other independent claim, even if the claim is not directly defined as dependent on the other independent claim.

Claims

1. An abnormal Hall sensor (100), comprising: Hall Cross (110), including: A layer stack (200) comprising a ferromagnetic layer (210), a first arm (114-1) of the Hall cross, formed in the layer stack and extending in a first direction, and a second arm (114-2) of the Hall cross, formed in the layer stack and extending in a second direction perpendicular to the first direction; a control circuit (120) configured to apply a current through the first arm (114-1) of the Hall cross and to measure a voltage across the second arm (114-2) of the Hall cross in response to the current through the first arm, applying a current through the second arm (114-2) of the Hall cross and measuring a voltage across the first arm (114-1) of the Hall cross in response to the current through the second arm; and A processor (130) is configured to calculate a component of an external magnetic field in a third direction perpendicular to the first direction and the second direction based on a combination of the measured voltages.

2. The abnormal Hall sensor (100) according to claim 1, wherein the control circuit (120) is configured to applying a first current and a second current through the first arm (114-1) of the Hall cross in opposite directions and measuring respective first and second voltages across the second arm (114-2) of the Hall cross in response to the respective currents, applying a third current and a fourth current through the second arm (114-2) of the Hall cross in opposite directions and measuring respective third and fourth voltages across the first arm (114-1) of the Hall cross in response to the respective currents, and The processor (130) is configured to calculate a 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 the component of the external magnetic field in the first direction based on a measured combination of the first voltage and the second voltage.

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 the measured sum of the first voltage and the second voltage.

5. The anomalous Hall sensor (100) according to any one of claims 2 to 4, wherein the processor (130) is configured to calculate the component of the external magnetic field in the second direction based on a measured combination of the third voltage and the fourth voltage.

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 the measured sum of the third voltage and the fourth voltage.

7. The anomalous Hall sensor (100) according to any one of claims 2 to 6, wherein the combination of four voltages measured includes a first difference between the third voltage and the fourth voltage and a second difference between the first voltage and the second voltage.

8. The anomalous Hall sensor (100) of claim 7, wherein the combination of four measured 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 electrically conductive non-magnetic layer (220) and the ferromagnetic layer (210).

10. The anomalous Hall sensor (100) of 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 consisting of a plurality of repetitions of non-magnetic layers and magnetic layers.

12. The anomalous Hall sensor (100) according to any one of the preceding claims, wherein the layer stack (200) comprises a multilayer consisting of a first non-magnetic layer (220), a magnetic layer (210), and a plurality of repetitions of 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 current into the arms of the Hall cross (110) as spin-polarized currents, respectively.

15. An abnormal Hall sensing method (400), comprising: applying (410) a current through a first arm of a Hall cross, the first arm extending in a first direction; measuring (420) a voltage across a second arm of the Hall cross in response to a current through the first arm; applying (430) a current through the second arm of the Hall cross, the second arm extending in a second direction perpendicular to the first direction; measuring (440) a voltage across the first arm of the Hall cross in response to a current through the second arm; as well as A component of an external magnetic field in a third direction perpendicular to the first direction and the second direction is calculated (450) based on the measured combination of the voltages.

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