MAGNETORESISTIVER SENSOR

Abstract

Proposed is a magnetoresistive sensor (100; 110) comprising a first magnetic reference layer (116-1), a second magnetic reference layer (116-2), and at least one magnetically free layer (118-1) embedded between the first and second magnetic reference layers. The first magnetic reference layer (116-1) has a first reference magnetization, and the second magnetic reference layer (116-2) has a second reference magnetization different from the first reference magnetization.

Description

Technical area

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

[0002] Technical solutions capable of measuring three components of a magnetic field are known, such as HHall (Horizontal Hall) and VHall (Vertical Hall) sensors. HHall and VHall sensors are specific types of Hall-effect sensors designed to measure magnetic fields in the horizontal (H) and vertical (V) directions relative to the surface of the sensor or the semiconductor material. Typically, "horizontal" or "vertical" refers to an orientation of a Hall plate. HHall sensors measure the components of the magnetic field that are perpendicular to the sensor surface. VHall sensors, in contrast to HHall sensors, are designed to measure the magnetic field components that are parallel to the sensor surface.

[0003] A trend toward integrating application-specific functions (such as digitally supported compensation algorithms, digital interfaces encoding additional information such as temperature or other safety-relevant information) is well-suited to integrated Hall technology. However, limitations of this technology lie in its SNR (signal-to-noise ratio) performance, which typically results in limited bandwidth or measurement range, and in the challenge of meeting analog interface requirements while maintaining low complexity and cost.

[0004] For example, 3D magnetic field sensors with improved SNR performance on all three channels that can also be integrated on a single chip are desirable. Summary

[0005] This need is met by magnetoresistive sensors according to the appended claims.

[0006] According to a first aspect, the present disclosure proposes a magnetoresistive sensor comprising a first magnetic reference layer, a second magnetic reference layer, and at least one magnetically free layer embedded between the first and second magnetic reference layers. The magnetoresistive sensor can be configured, for example, as a GMR sensor or as a TMR sensor. In particular, a combination of several such magnetoresistive sensors can be advantageously used for 3D magnetic field measurement with appropriate alignment of the reference magnetizations.

[0007] According to some embodiments, the first magnetic reference layer has a first reference magnetization, and the second magnetic reference layer has a second reference magnetization that is different from the first reference magnetization. For example, the first magnetic reference layer has an in-plane (parallel to a specific plane, typically the surface plane of the magnetoresistive sensor) reference magnetization, and the second magnetic reference layer has an out-of-plane (perpendicular to a specific plane, typically the surface plane of the magnetoresistive sensor) reference magnetization. This allows the magnetoresistive sensor to measure both in-plane components of an external magnetic field and its out-of-plane components.

[0008] According to some embodiments, the first magnetic reference layer (e.g., with in-plane reference magnetization) is arranged above the at least one magnetically free layer, and the second magnetic reference layer (e.g., with out-of-plane reference magnetization) is arranged below the at least one magnetically free layer. The (magnetic) layers thus constitute a vertical magnetoresistive layer stack.

[0009] According to some embodiments, the magnetoresistive sensor comprises a first and a second magnetically free layer embedded between the first and second reference layers. This allows for the provision of magnetically free layers optimized for different magnetic field components.

[0010] According to some embodiments, an electrically conductive layer is arranged between the first and second magnetically free layers. This allows current to flow through the magnetoresistive layer stack depending on the external magnetic field.

[0011] According to some embodiments, the at least one magnetically free layer exhibits vortex magnetization. A magnetic vortex is a state in ferromagnetic materials in which the magnetization is arranged in a circular configuration around a central point, with the magnetization at the center pointing out of plane. Vortex configurations can exhibit high thermal stability, low magnetic leakage, low power consumption, and advantageous sensor properties.

[0012] According to some embodiments, the at least one magnetic reference layer is coupled to an antiferromagnet.

[0013] According to some embodiments, the first magnetically free layer has an in-plane vortex magnetization under a vanishing external magnetic field, and the second magnetically free layer has a synthetic antiferromagnet (SAF) with an out-of-plane magnetization under a vanishing external magnetic field. The magnetically free layer with vortex magnetization can be optimized for in-plane components of an external magnetic field. The SAF can be optimized for out-of-plane components of the external magnetic field.

[0014] According to some embodiments, the first magnetic reference layer and / or the second magnetic reference layer each comprise a plurality of ferromagnetic and / or antiferromagnetic layers. For example, the magnetic reference layers can each be formed using exchange coupling between two ferromagnetic layers separated by a non-magnetic layer.

[0015] According to some embodiments, a first insulator layer is embedded between the first magnetic reference layer and the at least one magnetically free layer, and a second insulator layer is embedded between the second magnetic reference layer and the at least one magnetically free layer. In this way, a TMR sensor can be formed. Examples of the insulating layer are MgO, MgAlO, or AlO layers.

[0016] According to some embodiments, a first non-magnetic, electrically conductive layer is embedded between the first magnetic reference layer and the at least one magnetically free layer, and a second non-magnetic, electrically conductive layer is embedded between the second magnetic reference layer and the at least one magnetically free layer. In this way, a GMR sensor can be formed. The electrically conductive intermediate layer can be made of Cu, Cr, or Ag, for example.

[0017] According to a further aspect, a magnetoresistive sensor with a first and a second magnetoresistive sensor element is proposed. The first magnetoresistive sensor element comprises a first magnetic reference layer with a first reference magnetization and a second magnetic reference layer with a second reference magnetization, wherein the first and second reference magnetizations are perpendicular to one another. At least one first magnetically free layer is embedded between the first and second magnetic reference layers. The second magnetoresistive sensor element comprises a third magnetic reference layer with a third reference magnetization and a fourth magnetic reference layer with a fourth reference magnetization, wherein the third reference magnetization is opposite to the first reference magnetization and perpendicular to the fourth reference magnetization.At least a second, magnetically free layer is embedded between the third and fourth magnetic reference layers. Such a magnetoresistive sensor, or a combination of several such sensors, can enable 3D magnetic field measurement.

[0018] According to some embodiments, the first and third reference magnetizations are each in-plane reference magnetizations, and the second and fourth reference magnetizations are each out-of-plane reference magnetizations. Thus, the magnetoresistive sensor can measure in-plane (e.g., x, y) and out-of-plane (e.g., z) magnetic field components.

[0019] According to other embodiments, the first and third reference magnetizations are each out-of-plane reference magnetizations, and the second and fourth reference magnetizations are each in-plane reference magnetizations. Thus, the magnetoresistive sensor can measure in-plane (e.g., x, y) and out-of-plane (e.g., z) magnetic field components.

[0020] According to some embodiments, the first magnetic reference layer is arranged above the first magnetically free layer, and the second magnetic reference layer is arranged below the first magnetically free layer. The third magnetic reference layer is arranged above the second magnetically free layer, and the fourth magnetic reference layer is arranged below the second magnetically free layer.

[0021] According to some embodiments, the magnetoresistive sensor comprises an upper and a lower magnetically free layer embedded between the first and second magnetic reference layers, and an upper and a lower magnetically free layer embedded between the third and fourth magnetic reference layers. This allows for the provision of magnetically free layers optimized for different magnetic field components.

[0022] According to some embodiments, an electrically conductive layer is arranged between the upper and lower magnetically free layers. This allows current to flow through the respective layer stacks depending on the external magnetic field.

[0023] According to some embodiments, the first / second magnetically free layer each has a vortex magnetization.

[0024] According to some embodiments, the upper magnetically free layers each have an in-plane vortex magnetization in the presence of a vanishing external magnetic field. The vortex core can have an out-of-plane magnetization. The lower magnetically free layers each have a synthetic antiferromagnet with an out-of-plane magnetization in the presence of a vanishing external magnetic field. The magnetically free layers with vortex magnetization can be optimized for in-plane components of an external magnetic field. The SAFs can be optimized for out-of-plane components of the external magnetic field.

[0025] According to some embodiments, the magnetic reference layers each comprise a plurality of ferromagnetic and / or antiferromagnetic layers. In particular, the reference layers can be part of a respective synthetic antiferromagnet (SAF) comprising a first and a second ferromagnetic layer separated by a non-magnetic layer. An SAF can be used as the magnetic reference layer of the magnetoresistive sensor.

[0026] According to some embodiments, a first insulator layer is embedded between the first magnetic reference layer and the first magnetically free layer. A third insulator layer is embedded between the third magnetic reference layer and the second magnetically free layer. A second insulator layer is embedded between the second magnetic reference layer and the first magnetically free layer. A fourth insulator layer is embedded between the fourth magnetic reference layer and the second magnetically free layer. In this way, a TMR sensor can be formed.

[0027] According to some embodiments, a first non-magnetic, electrically conductive layer is embedded between the first magnetic reference layer and the first magnetically free layer. A third non-magnetic, electrically conductive layer is embedded between the third magnetic reference layer and the second magnetically free layer. A second non-magnetic, electrically conductive layer is embedded between the second magnetic reference layer and the magnetically free layer. A fourth non-magnetic, electrically conductive layer is embedded between the fourth magnetic reference layer and the magnetically free layer. In this way, a GMR sensor can be formed.

[0028] According to some embodiments, the magnetoresistive sensor further comprises an output circuit configured to output a signal proportional to a difference in the electrical resistances of the first and second magnetoresistive sensor elements for a first magnetic field component (e.g., in-plane) of a measured external magnetic field, and to output a signal proportional to a sum of the electrical resistances of the first and second magnetoresistive sensor elements for a second magnetic field component (e.g., out-of-plane) of the external magnetic field.

[0029] In other forms, a signal is proportional to a difference of the electrical resistances proportional to an out-of-plane magnetic field component and the sum of the electrical resistances proportional to an in-plane magnetic field component.

[0030] According to yet another aspect, a magnetoresistive sensor having a first and a second magnetoresistive sensor element is proposed. The first magnetoresistive sensor element comprises a first magnetic reference layer and a first magnetically free layer. The second magnetoresistive sensor element comprises a second magnetic reference layer and a second magnetically free layer. The first reference magnetization points out of the plane at a first angle. The first angle can, for example, be in a range from 20° to 70°, preferably 45°. The second reference magnetization points out of the plane at a second angle. The second angle can, for example, be in a range from 20°+90° to 70°+90°, preferably 135°.

[0031] Embodiments of the present disclosure enable 3D magnetic field sensors with improved SNR performance on all three channels, which can also be integrated on a single chip. Short character description

[0032] Some examples of devices and / or methods are explained in more detail below with reference to the accompanying figures. They show: Fig. 1 shows a magnetoresistive sensor according to a first embodiment of the present disclosure; Fig. 2 a Wheatstone bridge configuration of a magnetoresistive sensor; Fig. Figure 3A shows a transfer curve of a vortex disk and ring with a diameter of 500 nm and a thickness of 60 nm. Js = 1.0 T, A = 12 pJ / m; Fig. 3B shows the insensitivity of a vertical vortex transfer curve to in-plane fields; Fig. 4 an optimization of the vortex transfer curve with perpendicular anisotropy. The vortex disk has a diameter of 1000 nm and a thickness of 60 nm. Js = 1.75 T, A = 15 pJ / m. The perpendicular anisotropy with K1 has an easy axis in the perpendicular direction; Fig. 5 shows a magnetoresistive sensor according to a second embodiment of the present disclosure; Fig. 6 a comparison of vortex and SAF transfer curves, a SAF consists of two antiparallel coupled ferromagnetic layers with lateral dimensions of 500 nm x 500 nm x 4 nm. The RKKY coupling J RKKY = -0.5 mJ / m 2 . Js = 1.0 T, A = 10 pJ / m. Each layer has a vertical anisotropy with K1 = 0.28 MJ / m 3 ; and Fig. 7 shows a magnetoresistive sensor according to a third embodiment of the present disclosure. 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. These 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 or features, which may be implemented identically or in a modified form while providing the same or a similar function. Furthermore, the thickness of lines, layers, and / or regions in the figures 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 both 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 equivalently 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 described below 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 herein 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] The Fig. 1 shows a magnetoresistive (MR) sensor 100 according to an embodiment of the present disclosure.

[0038] The MR sensor 100 includes a first MR sensor element 110-1 and a second MR sensor element 110-2. An MR sensor element 110 refers to the smallest, individually addressable unit within the MR sensor 100 capable of detecting a change in an external magnetic field and converting it into an electrical signal. Each sensor element is based on a magnetoresistive effect, which describes a change in the electrical resistance of the material in the presence of a magnetic field. The specific functionality of a sensor element depends on the type of magnetoresistive effect used (GMR, TMR, etc.).

[0039] The two MR sensor elements 110-1, 110-2 are arranged laterally adjacent to each other, e.g., on a common (semiconductor) substrate within a chip. Depending on the application, more or fewer than two MR sensor elements 110 can be provided. The MR elements 110 comprise materials whose electrical resistance changes in the presence of an external magnetic field. This property can be exploited in a wide variety of applications, from magnetic field sensors to memory devices. A characteristic effect of MR elements is the change in electrical resistance due to an alignment of spin states of electrons under the influence of an external magnetic field. Depending on the material and structure, various magnetoresistive effects can be utilized, including anisotropic magnetoresistance (AMR), giant magnetoresistance (GMR), tunneling magnetoresistance (TMR), and colossal magnetoresistance (CMR).In the following, GMR and TMR sensor elements are considered in particular.

[0040] The first MR sensor element 110-1 comprises a magnetoresistive layer stack comprising a first magnetic reference layer 116-1 with a first reference magnetization, a second magnetic reference layer 116-2 with a second reference magnetization, and a first magnetically free layer 118-1 embedded between the first and second magnetic reference layers 116-1, 116-2. A magnetoresistive layer stack refers to an arrangement of thin layers of different materials used to generate the magnetoresistive effects (such as GMR or TMR). GMR layer stacks can consist of alternating layers of ferromagnetic and non-magnetic metals. The change in resistance occurs because the relative orientation of the magnetization in the ferromagnetic layers can be influenced by an external magnetic field, which changes the electron scattering at the interfaces between the layers.TMR layer stacks can contain a thin insulating layer (barrier layer) flanked by two ferromagnetic layers. Electrons can overcome this barrier through the quantum mechanical tunneling effect. The probability of tunneling, and thus the electrical resistance of the stack, depends on the relative magnetic alignment of the two ferromagnetic layers. The layer stacks can be fabricated using various thin-film technologies, such as sputter deposition or atomic layer deposition (ALD), which allow for the creation of thin layers with precisely controlled thickness and composition.

[0041] The first magnetic reference layer 116-1, arranged above the first magnetically free layer 118-1 in the first MR sensor element 110-1, can comprise a ferromagnetic layer that can have a high coercive field strength (it maintains its magnetic alignment in external magnetic fields). In other embodiments, the first magnetic reference layer 116-1 is stabilized with an antiferromagnet using "exchange bias." The blocking temperature of this first reference layer is T1.

[0042] The first magnetic reference layer 116-1 can serve as the first magnetic reference layer with which the orientation of the first magnetically free layer 118-1 is compared. In the Fig. In the example shown in Figure 1, a synthetic antiferromagnetic structure (SAF) is used for the first magnetic reference layer 116-1. SAFs can consist of two (or more) ferromagnetic layers 112, 114 separated by a non-magnetic coupling layer (e.g., ruthenium, Ru). Other 3d, 4d, and 5d transition metals such as V, Nb, Mo, Ta, W, Re, and Ir can also be used. The coupling layer (not shown) effects antiferromagnetic coupling between the ferromagnetic layers 112, 114. This arrangement can increase the stability of the magnetic alignment of the reference layer 116-1.

[0043] In the example shown, the first reference magnetization of the first magnetic reference layer 116-1 is an in-plane magnetization (e.g., in the +x direction). It is understood that the first reference magnetization could also point in a different direction in the (layer) plane (e.g., +y direction).

[0044] The second magnetic reference layer 116-2 arranged below the first magnetically free layer 118-1 in the first MR sensor element 110-1 may comprise a ferromagnetic layer that may have a high coercive field strength. The second magnetic reference layer 116-2 may serve as a second magnetic reference layer with which the orientation of the first magnetically free layer 118-1 is compared. In the Fig. In the example shown in Figure 1, a SAF structure is also used for the second magnetic reference layer 116-2. Additionally, the magnetization orientation of the SAF can be stabilized by an adjacent layer of an antiferromagnet (e.g., PtMn, IrMn) via the exchange bias effect. The blocking temperature of this second reference layer can be T2. The blocking temperatures T1 and T2 can be the same or different. In some cases, T1 > T2. In other cases, T1 < T2.

[0045] In the example shown, the second reference magnetization of the second magnetic reference layer 116-2 is an out-of-plane magnetization (e.g., in the +z direction). To realize an out-of-plane reference magnetization, materials and structures exhibiting strong perpendicular magnetic anisotropy (PMA) can be used. PMA is a form of magnetic anisotropy in which the energetically preferred direction of magnetization is perpendicular to the layer plane. This can be achieved by selecting suitable materials for the ferromagnetic layers and the adjacent layers, such as certain alloys or compounds applied using special thin-film deposition techniques. This can be achieved, for example, by using Co / Pt layer stacks in MR sensors.

[0046] The first magnetically free layer 118-1 can comprise a first ferromagnetic layer, which can be configured with a low coercive field strength (easily magnetizable and demagnetizable). The first ferromagnetic layer can serve as the first magnetically free layer 118-1 of the MR sensor 100. Example materials for the magnetically free layer 118-1 are NiFe (nickel-iron, also known as permalloy), CoFe (cobalt-iron), or CoFeB (cobalt-iron-boron). The magnetically free layer 118-1 can be a ferromagnet that forms a closed-plane flux state (vortex) at an external magnetic field of zero. In other embodiments, the first magnetically free layer 118-1 can be in a quasi-homogeneous state of in-plane magnetization at an external magnetic field of zero. In other embodiments, the first magnetically free layer 118-1 may also include a SAF.

[0047] Electrodes and terminals 120 are arranged at the upper and lower ends of the layer stack of the first MR sensor element 110-1. The first MR sensor element 110-1 forms a magnetic field-dependent electrical resistance R1.

[0048] The second MR sensor element 110-2 is similar to the first MR sensor element 110-1 and comprises a layer stack comprising a third magnetic reference layer 116-2 having a third reference magnetization, a fourth magnetic reference layer 116-4 having a fourth reference magnetization, and a second magnetically free layer 118-2 embedded between the third and fourth magnetic reference layers 116-3, 116-4.

[0049] The third magnetic reference layer 116-3 arranged above the second magnetically free layer 118-2 in the second MR sensor element 110-2 may comprise a ferromagnetic layer that may have a high coercive field strength. The third magnetic reference layer 116-3 may serve as a first magnetic reference layer with which the orientation of the second magnetically free layer 118-2 is compared. In the Fig. In the example shown in Figure 1, a SAF structure is used for the third magnetic reference layer 116-3. Additionally, the magnetization orientation of the SAF can be stabilized by an adjacent layer of an antiferromagnet (e.g., PtMn, IrMn) via the exchange bias effect.

[0050] In the example shown, the third reference magnetization of the third magnetic reference layer 116-3 is an in-plane magnetization opposite (e.g., in the -x direction) to the first reference magnetization of the first magnetic reference layer 116-1. It is understood that the third reference magnetization could also point in a different in-plane direction (e.g., -y direction).

[0051] The fourth magnetic reference layer 116-4 arranged below the second magnetically free layer 118-2 in the second MR sensor element 110-2 may comprise a ferromagnetic layer that may have a high coercive field strength. The fourth magnetic reference layer 116-4 may serve as a second magnetic reference layer with which the orientation of the second magnetically free layer 118-2 is compared. In the Fig. In the example shown in Figure 1, a SAF structure is also used for the fourth magnetic reference layer 116-4.

[0052] In the example shown, the fourth reference magnetization of the fourth magnetic reference layer 116-4 is an out-of-plane magnetization (e.g. in the +z direction) in the same direction as the second reference magnetization of the second magnetic reference layer 116-2.

[0053] The second magnetically free layer 118-2 may include a second ferromagnetic layer, which may be configured with a low coercive field strength (easily magnetizable and demagnetizable). The second ferromagnetic layer may serve as the second magnetically free layer 118-2 of the MR sensor 100 and may be configured substantially identically to the first magnetically free layer 118-1.

[0054] Electrodes or terminals 120 are also arranged at the upper and lower ends of the layer stack of the second MR sensor element 110-2. The second MR sensor element 110-2 forms a magnetic field-dependent electrical resistance R2.

[0055] According to some embodiments, a first insulator layer (not shown) is embedded between the first magnetic reference layer 116-1 and the first magnetically free layer 118-1. A second insulator layer (not shown) is embedded between the second magnetic reference layer 116-2 and the first magnetically free layer 118-1. A third insulator layer (not shown) is embedded between the third magnetic reference layer 116-3 and the second magnetically free layer 118-2. A fourth insulator layer (not shown) is embedded between the fourth magnetic reference layer 116-4 and the second magnetically free layer 118-2. In this way, a TMR sensor can be formed. The insulator layers are thin enough to enable the quantum mechanical tunneling effect. The insulator layers are also referred to as a tunnel barrier.Materials for the tunnel barrier can be, for example, aluminum oxide (Al2O3) or magnesium oxide (MgO).

[0056] According to other embodiments, a first non-magnetic, electrically conductive layer (not shown) is embedded between the first magnetic reference layer 116-1 and the first magnetically free layer 118-1. A second non-magnetic, electrically conductive layer (not shown) is embedded between the second magnetic reference layer 116-2 and the first magnetically free layer 118-1. A third non-magnetic, electrically conductive layer (not shown) is embedded between the third magnetic reference layer 116-3 and the second magnetically free layer 118-2. A fourth non-magnetic, electrically conductive layer (not shown) is embedded between the fourth magnetic reference layer 116-4 and the second magnetically free layer 118-2. In this way, a GMR sensor can be formed.The respective non-magnetic, electrically conductive layers can be made of a non-magnetic metal or an alloy. These layers enable giant magnetoresistance by acting as conductors for the electrons whose spin is influenced by the adjacent magnetic layers. Examples of materials for the non-magnetic intermediate layer in GMR sensors include copper (Cu), gold (Au), silver (Ag), aluminum (Al), or alloys.

[0057] Each MR sensor element 110 of the Fig. 1 contains at least one ferromagnetic free layer 118. This ferromagnetic free layer 118 is embedded between two magnetic reference systems 116 with different magnetization directions. In some embodiments, one of the reference systems 116-2 or 116-4 contains perpendicular magnetization (out-of-plane), and the other reference system 116-1 or 116-3 contains in-plane magnetization. Thus, the upper reference system 116-1 or 116-3 can have in-plane magnetization, and the lower reference system 116-2 or 116-4 can have out-of-plane magnetization. The reference systems 116 can each have two antiparallel coupled layers 112, 114, e.g., antiparallel coupled due to the RKKY interaction. Stability can be increased by coupling with an antiferromagnet.Different magnetization directions of a SAF system can be realized, for example, by laser annealing under the influence of an external magnetic field. For example, it is possible for the topmost layer in the in-plane reference system 116-1 to point in the +x direction, while in the adjacent in-plane reference system 116-3, the topmost layer can point in the -x direction. In other embodiments, the magnetization of the in-plane reference systems 116-1 and 116-3 can point in the +y and -y directions.

[0058] The perpendicular reference systems 116-2 and 116-4 can each comprise synthetic antiferromagnetic perpendicularly magnetized layers. Examples include multilayers such as Co / Pt or Co / Pd multilayers. These multilayers can be coupled antiparallel via RKKY coupling layers such as a Ru layer. Multiple RKKY layers could also be used.

[0059] Due to the two magnetic in-plane reference layers 116-1, 116-3 with opposite reference magnetization, the two MR elements 110-1, 110-2 have with respect to external magnetic field components in the x-direction (B x ) inverted transfer curves. For the magnetically free layers 118-1 and 118-2, for example, vortex magnetization can be used. However, other magnetically free layers corresponding to the state of the art can also be used.

[0060] The signal for B x -fields can therefore be determined by a difference in the resistances R1 and R2 of the two MR elements 110-1, 110-2 Signalx=R1−R2 An additional magnetic field component in the z-direction (B z), i.e., outside the plane, changes the resistances R1 and R2 of the two MR elements 110-1, 110-2 in the same way and only leads to a shift in the two resistances R1 and R2. The difference R1 - R2 therefore remains unchanged. The signal x is therefore not changed by out-of-plane fields.

[0061] On the other hand, magnetic field components in the z-direction (B z ) can be determined by adding the two resistors R1 and R2: Signalz=R1+R2

[0062] An additional magnetic field component in the x- or y-direction (B x , B y ), i.e., within the plane, increases one resistance R1 and decreases the other R2 (or vice versa). Therefore, the sum of the two resistances R1 and R2 remains unchanged with respect to the in-plane field.

[0063] The MR sensor 100 may further comprise an output circuit 130 coupled to the MR elements 110-1, 110-2, which is configured to generate a signal for an x-component (or y-component) of a measured external magnetic field x (or signal y ) proportional to a difference of the electrical resistances R1 and R2 of the MR elements 110-1, 110-2, and for a z-component of the external magnetic field a signal z proportional to a sum of the electrical resistances R1 and R2 of the MR elements 110-1, 110-2.

[0064] With the two MR elements 110-1, 110-2 shown, external magnetic fields can be detected in the x-direction and the z-direction. If additional MR elements with in-plane reference systems are implemented in the ±y-direction, y-fields can also be detected. Thus, with more than two MR elements 110 (such as four or six), which can be implemented with the same magnet stack, all three magnetic field components (x, y, z) can be detected.

[0065] The B x The field can also be read out in a Wheatstone bridge configuration, where two bridge resistors (in different bridge branches) can have the resistance R1 and two bridge resistors (in different bridge branches) can have the resistance R2. Such a Wheatstone bridge is shown schematically in Fig. 2 shown.

[0066] According to other embodiments, an MR sensor 100 with a first MR sensor element 110-1 and a second MR sensor element 110-2 can also be realized if two out-of-plane reference systems 116-2, 116-4 with antiparallel magnetization are implemented and the two in-plane reference systems 116-1, 116-3 have the same reference magnetization. The out-of-plane reference systems 116-2, 116-4 can also be reversed by Oersted fields or spin-orbit torque currents of adjacent heavy metal layers.

[0067] In Fig. 3A shows an example of a vortex-magnetized magnetically free layer 118 that is sensitive to external out-of-plane magnetic fields. Fig. Figure 3A shows a transfer curve 302 of a vortex disk and a transfer curve 304 of a vortex ring (without vortex core), each with a diameter of 500 nm and a thickness of 60 nm. Js = 1.0 T, A = 12 pJ / m. As in Fig. As can be seen in Figure 3A, the vortex disk and vortex ring respond fundamentally the same to an orthogonal (Bz) field. This change in the Mz component can be detected by the out-of-plane reference system 116-2 or 116-4. The vortex magnetization of the magnetically free layer 118-1 or 118-2 can have the advantage over purely in-plane magnetization of being more robust against in-plane fields.

[0068] Fig. Figure 3B shows an out-of-plane response of a vortex disk as a function of different Bx fields (0 mT, 50 mT, 100 mT). It can be seen that this response is essentially independent of the Bx fields. A detailed analysis can be found in Table 1. Here, linear fits of the transfer curve are shown. Mz / Ms=Bza+b for different Bx fields. It can be seen that the linear term a changes almost unchanged depending on the Bx fields. For a Bx field of 100 mT, the slope of the transfer curve changes by less than 0.2% compared to Bx=0. Table 1 Bx (mT) Slope a [1 / T] Change of slope a [%] 0 1.107 0.000 50 1.106 -0.090 100 1.105 -0.181

[0069] The sensitivity of the vortex-magnetized magnetic free layer 118-1 or 118-2 could be increased by introducing a perpendicular anisotropy in the z-direction. This could be achieved by using a magnetic free layer 118-1 or 118-2 made of a material with out-of-plane anisotropy. A soft magnetic free layer coupled with an out-of-plane magnetized layer could also be used.

[0070] In Fig. 4 shows a change in the vortex transfer curve depending on different vertical anisotropy constants K1 (reference numerals 402 for K1 = 0, 404 for K1 =0.2 MJ / m3 and 406 for K1= 0.5 MJ / m 3 ). For K1= 0.5 MJ / m 3 shape anisotropy is partially compensated, resulting in increased sensitivity.

[0071] The Fig. 5 shows a magnetoresistive (MR) sensor 200 according to another embodiment of the present disclosure.

[0072] The MR Sensor 200 of the Fig. 5 also has a first MR sensor element 210-1 and a second MR sensor element 210-2. The two MR sensor elements 210-1, 210-2 are arranged laterally adjacent to each other. Depending on the application, more or fewer than two MR sensor elements 210 may be provided.

[0073] The first MR sensor element 210-1 comprises two magnetically free layers embedded between the first and second magnetic reference layers 116-1, 116-2. The first MR sensor element 210-1 comprises a first magnetically free layer 118-11 and a second magnetically free layer 118-12 arranged thereunder. The two magnetically free layers 118-11, 118-12 can be made of different materials. In other embodiments, they are made of the same material but with different thicknesses and / or dimensions. The magnetically free layer 118-12 can be optimized for out-of-plane behavior. The magnetically free layer 118-11 can be optimized for in-plane behavior. These two layers 118-11, 118-12 can be exchange-decoupled. In the embodiment shown, a first electrically conductive layer 502-1 (e.g. made of Cu) is arranged between the first magnetically free layer 118-11 and the second magnetically free layer 118-12.In other forms, this layer can also be exchange-coupled and consist of a ferromagnetic or antiferromagnetic material.

[0074] The second MR sensor element 210-2 comprises a third magnetically free layer 118-21 and a fourth magnetically free layer 118-22 arranged thereunder. The two layers 118-21, 118-22 can be made of different materials. In other embodiments, they are made of the same material but with different thicknesses or dimensions. The magnetically free layer 118-22 can be optimized for out-of-plane behavior. The magnetically free layer 118-21 can be optimized for in-plane behavior. In the illustrated embodiment, a second electrically conductive layer 502-2 (e.g., made of Cu) is arranged between the third magnetically free layer 118-21 and the fourth magnetically free layer 118-22. In other embodiments, this layer can also be exchange-coupled and consist of a ferromagnetic or antiferromagnetic material.

[0075] The first magnetic reference layer 116-1 arranged above the first magnetically free layer 118-11 in the first MR sensor element 210-1 can comprise a ferromagnetic layer that can have a high coercive field strength (it maintains its magnetic alignment in external magnetic fields). This can be realized, for example, by coupling to an antiferromagnet. In embodiments according to the invention, an antiferromagnet can be realized above the reference layer 116-1. The first magnetic reference layer 116-1 can serve as a first magnetic reference layer with which the alignment of the first magnetically free layer 118-11 is compared. In the Fig. In the example shown in Figure 5, a synthetic antiferromagnetic structure (SAF) is used for the first magnetic reference layer 116-1. In the example shown, the first reference magnetization of the first magnetic reference layer 116-1 is an in-plane magnetization (e.g., in the +x direction). It is understood that the first reference magnetization could also point in a different direction (e.g., +y direction).

[0076] The second magnetic reference layer 116-2 arranged below the second magnetically free layer 118-12 in the first MR sensor element 210-1 can comprise a ferromagnetic layer that can have a high coercive field strength. This can be realized, for example, by coupling to an antiferromagnet. In embodiments according to the invention, an antiferromagnet can be realized above the reference layer 116-1. The second magnetic reference layer 116-2 can serve as a second magnetic reference layer with which the orientation of the second magnetically free layer 118-12 is compared. In the Fig. In the example shown in Figure 5, a SAF structure is also used for the second magnetic reference layer 116-2.

[0077] In the example shown, the second reference magnetization of the second magnetic reference layer 116-2 is an out-of-plane magnetization (e.g. in the +z direction).

[0078] Electrodes and terminals 120 are arranged at the upper and lower ends of the layer stack of the first MR sensor element 210-1. The first MR sensor element 210-1 forms a magnetic field-dependent electrical resistance R1.

[0079] The third magnetic reference layer 116-3 arranged above the third magnetically free layer 118-12 in the second MR sensor element 210-2 may comprise a ferromagnetic layer that may have a high coercive field strength. The third magnetic reference layer 116-3 may serve as a first magnetic reference layer with which the orientation of the third magnetically free layer 118-12 is compared. In the Fig. In the example shown in Figure 5, a SAF structure is used for the third magnetic reference layer 116-3.

[0080] In the example shown, the third reference magnetization of the third magnetic reference layer 116-3 is an in-plane magnetization opposite (e.g., in the -x direction) to the first reference magnetization of the first magnetic reference layer 116-1. It is understood that the third reference magnetization could also point in a different direction (e.g., -y direction). Antiferromagnets can also be used here to increase stability.

[0081] The fourth magnetic reference layer 116-4 arranged below the fourth magnetically free layer 118-22 in the second MR sensor element 210-2 may comprise a ferromagnetic layer that may have a high coercive field strength. The fourth magnetic reference layer 116-4 may serve as a second magnetic reference layer with which the orientation of the fourth magnetically free layer 118-22 is compared. In the Fig. In the example shown in Figure 5, a SAF structure is also used for the fourth magnetic reference layer 116-4.

[0082] In the example shown, the fourth reference magnetization of the fourth magnetic reference layer 116-4 is an out-of-plane magnetization opposite (e.g., in the -z direction) to the second reference magnetization of the second magnetic reference layer 116-2.

[0083] Electrodes or terminals 120 are also arranged at the upper and lower ends of the layer stack of the second MR sensor element 210-2. The second MR sensor element 210-2 forms a magnetic field-dependent electrical resistance R2.

[0084] According to some embodiments, a first insulator layer or tunnel barrier (not shown) is embedded between the first magnetic reference layer 116-1 and the first magnetically free layer 118-11. A second insulator layer (not shown) is embedded between the second magnetic reference layer 116-2 and the second magnetically free layer 118-12. A third insulator layer (not shown) is embedded between the third magnetic reference layer 116-3 and the third magnetically free layer 118-21. A fourth insulator layer (not shown) is embedded between the fourth magnetic reference layer 116-4 and the fourth magnetically free layer 118-22. In this way, a TMR sensor can be formed.

[0085] According to other embodiments, a first non-magnetic, electrically conductive layer (not shown) is embedded between the first magnetic reference layer 116-1 and the first magnetically free layer 118-11. A second non-magnetic, electrically conductive layer (not shown) is embedded between the second magnetic reference layer 116-2 and the second magnetically free layer 118-12. A third non-magnetic, electrically conductive layer (not shown) is embedded between the third magnetic reference layer 116-3 and the third magnetically free layer 118-21. A fourth non-magnetic, electrically conductive layer (not shown) is embedded between the fourth magnetic reference layer 116-4 and the fourth magnetically free layer 118-22. In this way, a GMR sensor can be formed.

[0086] The MR Sensor 200 according to Fig. 5 may further comprise an output circuit 130 coupled to the MR elements 210-1, 210-2, which is configured to generate a signal for an x-component (or y-component) of a measured external magnetic field x (or signal y ) proportional to a difference of the electrical resistances R1 and R2 of the MR elements 210-1, 210-2, and for a z-component of the external magnetic field a signal signal z proportional to a sum of the electrical resistances R1 and R2 of the MR elements 210-1, 210-2.

[0087] In Fig. 6, an exemplary magnetically free layer 118-12 or 118-22, which is optimized for out-of-plane behavior, is compared with a vortex-magnetized free layer. The out-of-plane optimized magnetically free layer 118-12 or 118-22 can consist of two antiferromagnetically coupled layers with magnetization parallel to the plane. When an external out-of-plane field is applied, the Mz component of the magnetically free layer 118-12 or 118-22, which can also be a SAF, depends linearly on the Hz field. To increase the sensitivity of the free SAF layer 118-12 or 118-22, it can, for example, be provided with a perpendicular anisotropy of K1 = 0.28 MJ / m 3 be realized.

[0088] Due to the SAF coupling, the magnetically free layer 118-12 or 118-22 is also insensitive to Bx fields, as in Fig. 6. Table 2 shows that the slope of the transfer function of the free SAF layer changes by 0.6% when a Bx field of 50 mT (7% of the linear range) is applied, compared to Bx = 0. Table 2 Bx (mT) Slope a [1 / T] Change of slope a [%] 0 1.465 0.000 50 1.4557 -0.635

[0089] Other layers that may also be suitable as out-of-plane optimized magnetic free layers 118-12, 118-22 may be, for example, multi-domain states with perpendicular anisotropy or free layers in the plane.

[0090] The in-plane optimized magnetic free layers 118-11 and 118-12 could be layers with a vortex state (such as a vortex disk) or synthetic antiferromagnetically coupled in-plane free layers with shape anisotropy.

[0091] As an alternative to a thick magnetically free vortex layer for combined in-plane and out-of-plane detection, a very thin free layer with perpendicular anisotropy in a superparamagnetic state between both reference frames 116-1, 116-2 could be used.

[0092] Another possible embodiment of an MR sensor is in the Fig. 7. The Fig. 7 shows a possible MR sensor 700 comprising a first MR sensor element 710-1 and a second MR sensor element 710-2.

[0093] The first MR sensor element 710-1 has a first magnetic reference layer 716-1 with a first reference magnetization. The first reference magnetization points out of the plane of the reference layer 716-1 at a first angle. The first angle can, for example, be in a range from 20° to 70°, preferably 45°. The first MR sensor element 710-1 also has a first magnetically free layer 118-1 (e.g., with vortex magnetization). Depending on the embodiment, the first magnetically free layer 118-1 and the first magnetic reference layer 716-1 are separated by a tunnel barrier (TMR) or a non-magnetic, electrically conductive layer (GMR).

[0094] Electrodes and terminals 120 are arranged at the upper and lower ends of the layer stack of the first MR sensor element 710-1. The first MR sensor element 710-1 forms a magnetic field-dependent electrical resistance R1.

[0095] The second MR sensor element 710-2 has a second magnetic reference layer 716-2 with a second reference magnetization that is different (e.g., perpendicular) to the first reference magnetization. The second reference magnetization points at a second angle out of the plane of the reference layer 716-2. The second angle can, for example, be in a range from 20°+90°=110° to 70°+90°=160°, preferably 135°. The second MR sensor element 710-2 also has a second magnetically free layer 118-2 (e.g., with vortex magnetization). Depending on the embodiment, the second magnetically free layer 118-2 and the second magnetic reference layer 716-2 are separated by a tunnel barrier (TMR) or a non-magnetic, electrically conductive layer (GMR).

[0096] Electrodes or terminals 120 are also arranged at the upper and lower ends of the layer stack of the second MR sensor element 710-2. The second MR sensor element 710-2 forms a magnetic field-dependent electrical resistance R2.

[0097] The MR sensor 700 may include an output circuit 130 coupled to the MR elements 710-1, 710-2, which is configured to generate a signal for an x-component (or y-component) of a measured external magnetic field x (or signal y ) proportional to a difference of the electrical resistances R1 and R2 of the MR elements 710-1, 710-2, and for a z-component of the external magnetic field a signal z proportional to a sum of the electrical resistances R1 and R2 of the MR elements 710-1, 710-2.

[0098] Orienting the reference magnetization in the reference layers 716 to an angle of, for example, 45° out-of-plane can present a certain technical challenge. Aligning the magnetization at an intermediate angle such as 45° relative to the plane may require a specific balance of magnetic anisotropy, both in-plane and perpendicular to it. Achieving a partially out-of-plane orientation may involve complex layer structures or special material combinations exhibiting both in-plane and out-of-plane anisotropies. These could be modified by external fields during deposition or by subsequent thermal or mechanical treatments.

[0099] 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.

[0100] 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 technically required. 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.

[0101] If some aspects in the preceding sections were described in connection with a device or system, these aspects are also to be understood as a description of the corresponding method. For example, a block, a device, or a functional aspect of the device 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 device or system.

[0102] The following claims are hereby incorporated into the Detailed Description, each claim being understood to 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 included, even if that claim is not directly defined as dependent on that other independent claim.

Claims

[1] Magnetoresistive sensor (100; 110), comprising a first magnetic reference layer (116-1); a second magnetic reference layer (116-2); and at least one magnetically free layer (118-1) embedded between the first and the second magnetic reference layer. [2] Magnetoresistive sensor (100; 110) according to claim 1, wherein the first magnetic reference layer (116-1) has a first reference magnetization and the second magnetic reference layer (116-2) has a second reference magnetization, different from the first reference magnetization. [3] Magnetoresistive sensor (100; 110) according to claim 1 or 2, wherein the first magnetic reference layer (116-1) has an in-plane reference magnetization and the second magnetic reference layer (116-2) has an out-of-plane reference magnetization. [4] Magnetoresistive sensor (100; 110) according to one of the preceding claims, comprising a first magnetically free layer (118-11) and a second magnetically free layer (118-12) embedded between the first and the second reference layer (116-1; 116-2). [5] Magnetoresistive sensor (100; 110) according to claim 4, wherein an electrically conductive layer is arranged between the first and the second magnetically free layer (118-11; 118-12). [6] Magnetoresistive sensor (100; 110) according to claim 4 or 5, wherein the first magnetically free layer (118-11) has an in-plane vortex magnetization with vanishing external magnetic field and the second magnetically free layer (118-12) has a synthetic antiferromagnet with an out-of-plane magnetization with vanishing external magnetic field. [7] Magnetoresistive sensor (100; 110) according to one of the preceding claims, wherein the first magnetic reference layer (116-1) and / or the second magnetic reference layer (116-2) each comprise a plurality of ferromagnetic and / or antiferromagnetic layers. [8] Magnetoresistive sensor (100; 110) according to one of the preceding claims, wherein a first insulating layer is embedded between the first magnetic reference layer (116-1) and the at least one magnetically free layer (118-1) and a second insulating layer is embedded between the second magnetic reference layer (116-2) and the at least one magnetically free layer (118-1). [9] Magnetoresistive sensor (100; 110) according to any one of claims 1 to 8, wherein a first non-magnetic, electrically conductive layer is embedded between the first magnetic reference layer (116-1) and the at least one magnetically free layer (118-1) and a second non-magnetic, electrically conductive layer is embedded between the second magnetic reference layer (116-2) and the at least one magnetically free layer (118-1). [10] Magnetoresistive sensor (100; 110) according to one of the preceding claims, wherein the at least one magnetically free layer (118-1) has a vortex magnetization. [11] Magnetoresistive sensor (100; 200), comprising a first magnetoresistive sensor element (110-1) with a first magnetic reference layer (116-1) with a first reference magnetization; a second magnetic reference layer (116-1) with a second reference magnetization, where the first and second reference magnetizations are perpendicular to each other; and at least one first magnetically free layer (118-1) embedded between the first and the second magnetic reference layer; and a second magnetoresistive sensor element (110-2) with a third magnetic reference layer (116-3) with a third reference magnetization; a fourth magnetic reference layer (116-4) with a fourth reference magnetization, wherein the third reference magnetization is opposite to the first reference magnetization and perpendicular to the fourth reference magnetization; and at least one second magnetically free layer (118-2) embedded between the first and the second magnetic reference layer. [12] Magnetoresistive sensor (100; 200) according to claim 11, wherein the first and third reference magnetizations are in-plane reference magnetizations and the second and fourth reference magnetizations are out-of-plane reference magnetizations. [13] Magnetoresistive sensor (100; 200) according to one of claims 11 or 12, wherein the first and the second magnetically free layer (118-1; 118-2) each have a vortex magnetization. [14] Magnetoresistive sensor (100; 200) according to one of claims 11 to 13, comprising an upper magnetically free layer (118-11) and a lower magnetically free layer (118-12) embedded between the first and second magnetic reference layers; and an upper magnetically free layer (118-21) and a lower magnetically free layer (118-22) embedded between the third and fourth magnetic reference layers. [15] Magnetoresistive sensor (100; 200) according to claim 14, wherein an electrically conductive layer is arranged between the upper and lower magnetically free layers (118-11; 118-12; 118-21; 118-22). [16] Magnetoresistive sensor (100; 200) according to claim 14 or 15, wherein the upper magnetically free layers (118-11; 118-21) each have an in-plane vortex magnetization with vanishing external magnetic field and the lower magnetically free layers (118-12; 118-22) each have a synthetic antiferromagnet with an in-plane magnetization with vanishing external magnetic field. [17] Magnetoresistive sensor (100; 200) according to any one of claims 11 to 16, wherein the magnetic reference layers each comprise a plurality of ferromagnetic and / or antiferromagnetic layers. [18] Magnetoresistive sensor (100; 200) according to one of claims 11 to 17, further comprising an output circuit (130) configured to output a signal proportional to a difference of the electrical resistances of the first and second magnetoresistive sensor elements (110-1; 110-2) for a first magnetic field component of a measured external magnetic field, and to output a signal proportional to a sum of the electrical resistances of the first and second magnetoresistive sensor elements (110-1; 110-2) for a second magnetic field component of the external magnetic field.

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