Magnetoresistive sensor

Abstract

The invention relates to a magnetoresistive sensor (100; 110) comprising a first magnetic reference layer (116-1), a second magnetic reference layer (116-2), and at least one magnetic 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 Field

[0001] The present disclosure relates generally to magnetoresistive sensors, and more particularly to magnetoresistive sensors capable of performing three-dimensional (3D) magnetic field measurements. Background Art

[0002] Technical solutions capable of measuring three components of a magnetic field, such as HHall (Horizontal Hall) and VHall (Vertical Hall) sensors, are known. 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 semiconductor material. Typically, "horizontal" or "vertical" refers to the orientation of the Hall plate. HHall sensors measure the component of the magnetic field that extends perpendicular to the sensor's surface. Unlike HHall sensors, VHall sensors are designed to measure the component of the magnetic field that extends parallel to the sensor's surface.

[0003] The trend toward integrating application-specific functions (e.g., digitally supported compensation algorithms, digital interfaces in which additional information, such as temperature or other safety-related information, is encoded) is well-suited for integrated Hall technology. However, limitations of this technology lie, on the one hand, in the signal-to-noise ratio (SNR), which often results in a limited bandwidth or a restricted measuring range. On the other hand, meeting the requirements for analog interfaces combined with reduced complexity and cost is a challenge.

[0004] For example, 3D magnetic field sensors with improved signal-to-noise performance on all three channels are desired, which can also be integrated on a single chip. Summary of the Invention

[0005] The magnetoresistive sensor according to the present invention meets this need.

[0006] According to a first aspect, the present invention provides a magnetoresistive sensor comprising a first magnetic reference layer, a second magnetic reference layer, and at least one magnetic free layer embedded between the first and second magnetic reference layers. The magnetoresistive sensor can be configured, for example, as a GMR sensor or a TMR sensor. In particular, a combination of multiple such magnetoresistive sensors can be advantageously used for 3D magnetic field measurement with corresponding orientations of the reference magnetization.

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

[0008] According to some embodiments, a first magnetic reference layer (e.g., having an in-plane reference magnetization) is disposed above at least one magnetic free layer, and a second magnetic reference layer (e.g., having an out-of-plane reference magnetization) is disposed below at least one magnetic free layer. The (magnetic) layers are a vertical magnetoresistive layer stack.

[0009] According to some embodiments, the magnetoresistive sensor includes first and second magnetic free layers embedded between a first reference layer and a second reference layer, thereby providing optimized magnetic free layers for different magnetic field components.

[0010] According to some embodiments, a conductive layer is disposed between the first magnetic free layer and the second magnetic free layer, thereby allowing current to flow through the magnetoresistive layer stack according to an external magnetic field.

[0011] According to some embodiments, at least one magnetically free layer has eddy current magnetization. Magnetic eddy current is a state in ferromagnetic materials in which magnetization is arranged in a circular configuration around a central point, where the magnetization in the center can point out of the plane (out of plane). The eddy current configuration can have high thermal stability, low magnetic scattering, low energy consumption, and favorable sensing properties.

[0012] According to some embodiments, 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 eddy current magnetization in the absence of an external magnetic field, and the second magnetically free layer has a synthetic antiferromagnet (SAF) with an out-of-plane magnetization in the absence of an external magnetic field. The magnetically free layer with the eddy current magnetization can be optimized for the in-plane component of the external magnetic field. The SAF can be optimized for the out-of-plane component of the external magnetic field.

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

[0015] In some embodiments, a first insulator layer is embedded between a first magnetic reference layer and at least one magnetic free layer, and a second insulator layer is embedded between a second magnetic reference layer and at least one magnetic free layer. This method can form a TMR sensor. Examples of the insulating layer are MgO, MgAlO, or AlO.

[0016] According to some embodiments, a first nonmagnetic conductive layer is embedded between a first magnetic reference layer and at least one magnetic free layer, and a second nonmagnetic conductive layer is embedded between a second magnetic reference layer and at least one magnetic free layer. This method can form a GMR sensor. The conductive intermediate layer can be composed of, for example, Cu, Cr, or Ag.

[0017] According to another aspect, a magnetoresistive sensor is provided that includes first and second magnetoresistive sensor elements. The first magnetoresistive sensor element includes a first magnetic reference layer having a first reference magnetization and a second magnetic reference layer having a second reference magnetization, wherein the first and second reference magnetizations are perpendicular to each other. At least a first magnetically free layer is embedded between the first and second magnetic reference layers. The second magnetoresistive sensor element includes a third magnetic reference layer having a third reference magnetization and a fourth magnetic reference layer having 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. This magnetoresistive sensor, or a combination of multiple such sensors, enables 3D magnetic field measurement.

[0018] According to some embodiments, the first and third reference magnetizations are in-plane reference magnetizations, and the second and fourth reference magnetizations are out-of-plane reference magnetizations. Thus, the magnetoresistive sensor can measure both 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 out-of-plane reference magnetizations, and the second and fourth reference magnetizations are in-plane reference magnetizations. Thus, the magnetoresistive sensor can measure both 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 disposed above the first magnetic free layer, and the second magnetic reference layer is disposed below the first magnetic free layer. The third magnetic reference layer is disposed above the second magnetic free layer, and the fourth magnetic reference layer is disposed below the second magnetic free layer.

[0021] According to some embodiments, a magnetoresistive sensor includes upper and lower magnetic free layers embedded between first and second magnetic reference layers, and upper and lower magnetic free layers embedded between third and fourth magnetic reference layers. Thus, magnetic free layers optimized for different magnetic field components can be provided.

[0022] According to some embodiments, a conductive layer is disposed between the upper magnetic free layer and the lower magnetic free layer, respectively, thereby allowing current to flow through the corresponding layer stack according to an external magnetic field.

[0023] According to some embodiments, the first and second magnetically free layers each have eddy current magnetization.

[0024] According to some embodiments, the upper magnetically free layer may have an in-plane eddy current magnetization in the absence of an external magnetic field. The eddy current core may have an out-of-plane magnetization. The lower magnetically free layer may have a synthetic antiferromagnet with an out-of-plane magnetization in the absence of an external magnetic field. The magnetically free layer with the eddy current magnetization may be optimized for the in-plane component of the external magnetic field. The SAF may be optimized for the out-of-plane component of the external magnetic field.

[0025] According to some embodiments, the magnetic reference layer includes multiple ferromagnetic and / or antiferromagnetic layers. In particular, the reference layer can be part of a corresponding synthetic antiferromagnet (SAF), which includes first and second ferromagnetic layers separated by a nonmagnetic layer. The SAF can be used as a magnetic reference layer for a magnetoresistive sensor.

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

[0027] According to some embodiments, a first nonmagnetic conductive layer is embedded between a first magnetic reference layer and a first magnetic free layer. A third nonmagnetic conductive layer is embedded between a third magnetic reference layer and a second magnetic free layer. A second nonmagnetic conductive layer is embedded between a second magnetic reference layer and a magnetic free layer. A fourth nonmagnetic conductive layer is embedded between a fourth magnetic reference layer and a magnetic free layer. In this manner, 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 the difference in resistances of the first and second magnetoresistive sensor elements for a first magnetic field component (e.g., in-plane) of the measured external magnetic field, and to output a signal proportional to the sum of the 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 designs, the signal proportional to the difference in signal resistance is proportional to the out-of-plane magnetic field component, and the sum of the resistances is proportional to the in-plane magnetic field component.

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

[0031] Embodiments of the present disclosure enable a 3D magnetic field sensor with improved signal-to-noise performance on all three channels, which can furthermore be integrated on a single chip. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Some examples of the apparatus and / or method are explained in detail below with reference to the accompanying drawings, which are merely exemplary.

[0033] Figure 1 A magnetoresistive sensor according to a first embodiment of the present disclosure is shown;

[0034] Figure 2 shows a Wheatstone bridge configuration for a magnetoresistive sensor;

[0035] Figure 3A The transfer curves for a vortex disk and a vortex ring with a diameter of 500 nm and a thickness of 60 nm are shown. Js = 1.0 T, A = 12 pJ / m;

[0036] Figure 3B The insensitivity of the vertical eddy current transfer curve to the in-plane field is shown;

[0037] Figure 4 Optimization of the eddy current transfer curve with perpendicular anisotropy is shown. The eddy current disk has a diameter of 1000 nm and a thickness of 60 nm. Js = 1.75 T, A = 15 pJ / m. Perpendicular anisotropy with K1 has an easy axis in the perpendicular direction.

[0038] Figure 5 shows a magnetoresistive sensor according to a second embodiment of the present disclosure;

[0039] Figure 6 Figure 2 shows a comparison of the eddy current transfer curve and the SAF transfer curve, which consists of two antiparallel coupled ferromagnetic layers with lateral dimensions of 500nm x 500nm x 4nm. RKKY =-0.5mJ / m 2 Js = 1.0 T, A = 10 pJ / m. Each layer has a K1 = 0.28 MJ / m 3perpendicular anisotropy; and

[0040] Figure 7 A magnetoresistive sensor according to a third embodiment of the present disclosure is shown. DETAILED DESCRIPTION

[0041] 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 the embodiments described in detail. The other possible examples may have modifications of the features and equivalents and alternatives of the features. In addition, the terms used in this article to describe specific examples should not limit other possible examples.

[0042] Throughout the description of the drawings, identical or similar reference numerals refer to identical or similar elements or features, which may be implemented identically or also in modified form, while providing identical or similar functions. In the drawings, the thickness of lines, layers, and / or regions may also be exaggerated for illustrative purposes.

[0043] When two elements A and B are combined using "or", it should be understood that all possible combinations, i.e., only A, only B, and A and B, are disclosed, unless expressly defined otherwise in individual cases. As an alternative expression of the same combination, "at least one of A and B" or "A and / or B" can be used, which corresponds to a combination of more than two elements.

[0044] If singular forms such as "a," "an," and "the" are used and the use of only one element is neither explicitly nor implicitly defined as mandatory, then alternative examples may also use multiple elements to achieve the same functionality. If a function is subsequently described as being achieved using multiple elements, then alternative examples may achieve the same functionality using a single element or a single processing entity. It is also to be understood that the terms "comprising," "having," and "including," when used herein, describe the presence of stated features, integers, steps, operations, processes, elements, components, and / or their components, but do not exclude the presence or addition of one or more additional features, integers, steps, operations, processes, elements, components, and / or their components.

[0045] Figure 1 A magnetoresistive (MR) sensor 100 is shown in accordance with an embodiment of the present disclosure.

[0046] MR sensor 100 includes a first MR sensor element 110-1 and a second MR sensor element 110-2. An MR sensor element 110 is the smallest, individually addressable unit within MR sensor 100 that can detect changes in an external magnetic field and convert them into an electrical signal. Each sensor element is based on the magnetoresistive effect, which describes the change in electrical resistance of a material in the presence of a magnetic field. The specific function of the sensor element depends on the type of magnetoresistive effect used (GMR, TMR, etc.).

[0047] Two MR sensor elements 110-1, 110-2 are arranged laterally adjacent to each other, for example on a common (semiconductor) substrate within a chip. Depending on the application, more or fewer MR sensor elements 110 can also be provided. The MR element 110 comprises a material whose electrical resistance changes in the presence of an external magnetic field. This property can be used in a variety of applications, from magnetic field sensors to storage devices. The characteristic effect of an MR element is the change in resistance due to the orientation of the spin states of the electrons under the influence of an external magnetic field. Depending on the material and structure, different magnetoresistance effects can be used, including anisotropic magnetoresistance (AMR), giant magnetoresistance (GMR), tunnel magnetoresistance (TMR) and super magnetoresistance (CMR). In the following, GMR and TMR sensor elements are considered in particular.

[0048] First MR sensor element 110-1 includes a magnetoresistive layer stack comprising a first magnetic reference layer 116-1 having a first reference magnetization, a second magnetic reference layer 116-2 having 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 produce a magnetoresistive effect, such as GMR or TMR. A GMR layer stack can consist of alternating layers of ferromagnetic and nonmagnetic metals. Changes in resistance occur because the relative orientation of the magnetizations in the ferromagnetic layers can be influenced by an external magnetic field, which changes electron scattering at the interface between the layers. A TMR layer stack can include a thin insulating layer (barrier layer) flanked by two ferromagnetic layers. Electrons can overcome this barrier through quantum mechanical tunneling. The probability of tunneling, and therefore the resistance of the stack, is related to the relative magnetic orientation of the two ferromagnetic layers. The layer stack can be produced by means of various thin-film technologies, such as sputtering deposition or atomic layer deposition (ALD), whereby thin layers with precisely controlled thickness and composition can be produced.

[0049] In first MR sensor element 110-1, first magnetic reference layer 116-1, disposed above first magnetically free layer 118-1, may include a ferromagnetic layer that may have high coercivity (maintains its magnetic orientation in an external magnetic field). In other designs, first magnetic reference layer 116-1 is stabilized by an antiferromagnetic element via an exchange bias. The blocking temperature of the first reference layer is T1.

[0050] The first magnetic reference layer 116-1 can be used as a first magnetic reference layer, and the orientation of the first magnetic free layer 118-1 is compared with the first magnetic reference layer. Figure 1 In the example shown, a synthetic antiferromagnetic structure (SAF) is used for the first magnetic reference layer 116-1. The SAF can be composed of two (or more) ferromagnetic layers 112 and 114 separated by a nonmagnetic coupling layer (e.g., ruthenium). 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) causes antiferromagnetic coupling between the ferromagnetic layers 112 and 114. This arrangement can improve the stability of the magnetic orientation of the reference layer 116-1.

[0051] In the example shown, the first reference magnetization of the first magnetic reference layer 116 - 1 is an in-plane magnetization (eg, in the +x direction). It is understood that the first reference magnetization may also point in other directions in the (layer) plane (eg, the +y direction).

[0052] The second magnetic reference layer 116-2 disposed below the first magnetic free layer 118-1 in the first MR sensor element 110-1 may include a ferromagnetic layer that may have high coercivity. The second magnetic reference layer 116-2 may serve as a second magnetic reference layer to which the orientation of the first magnetic free layer 118-1 is compared. Figure 1 In the example shown, 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 composed of an antiferromagnet (e.g., PtMn, IrMn) via an exchange bias effect. The blocking temperature of the second reference layer can be T2. The blocking temperatures T1 and T2 can be the same, but can also be different. In some designs, T1>T2. In other designs, T1 <T2。

[0053] 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). Materials and structures with strong perpendicular magnetic anisotropy (PMA) can be used to achieve the out-of-plane reference magnetization. PMA is a form of magnetic anisotropy in which the energy-preferred magnetization direction is perpendicular to the layer plane. This can be achieved by selecting suitable materials for the ferromagnetic layer and adjacent layers, such as specific alloys or compounds, which are applied using specialized thin-film deposition techniques. This can be achieved, for example, by using a Co / Pt layer stack in the MR sensor.

[0054] The first magnetically free layer 118-1 can include a first ferromagnetic layer that can be implemented with low coercivity (slightly 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 ferromagnetic material that forms a closed flow state (eddy current or turbulent flow) in a plane when the external magnetic field is zero. In other embodiments, the first magnetically free layer 118-1 can be in a quasi-uniform magnetization state in a plane when the external magnetic field is zero. In other embodiments, the first magnetically free layer 118-1 can also include a SAF.

[0055] Electrodes or contacts 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 resistance R1 that is dependent on the magnetic field.

[0056] Second MR sensor element 110 - 2 is similar to first MR sensor element 110 - 1 and includes a layer stack including a third magnetic reference layer 116 - 2 having a third reference magnetization, a fourth magnetic reference layer 118 - 4 having a fourth reference magnetization, and a second magnetic free layer 118 - 2 embedded between third and fourth magnetic reference layers 116 - 3 , 116 - 4 .

[0057] The third magnetic reference layer 116-3 disposed above the second magnetic free layer 118-2 in the second MR sensor element 110-2 may include a ferromagnetic layer that may have high coercivity. The third magnetic reference layer 116-3 may serve as a first magnetic reference layer, with the orientation of the second magnetic free layer 118-2 being compared to the third magnetic reference layer. Figure 1 In the example shown, 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 composed of an antiferromagnet (eg, PtMn, IrMn) via an exchange bias effect.

[0058] In the example shown, the third reference magnetization of the third magnetic reference layer 116-3 is an in-plane magnetization (e.g., in the −x direction) that is opposite to the first reference magnetization of the first magnetic reference layer 116-1. It is understood that the third reference magnetization can also point in other directions in the plane (e.g., in the −y direction).

[0059] The fourth magnetic reference layer 116-4 disposed below the second magnetic free layer 118-2 in the second MR sensor element 110-2 may include a ferromagnetic layer that may have high coercivity. The fourth magnetic reference layer 116-4 may serve as a second magnetic reference layer to which the orientation of the second magnetic free layer 118-2 is compared. Figure 1 In the example shown, the SAF structure is also used for the fourth magnetic reference layer 116 - 4 .

[0060] In the example shown, the fourth reference magnetization of the fourth magnetic reference layer 116 - 4 is an out-of-plane magnetization in the same direction as the second reference magnetization of the second magnetic reference layer 116 - 2 (eg, in the +z direction).

[0061] The second magnetically free layer 118-2 may include a second ferromagnetic layer that may be implemented with low coercivity (slightly 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 constructed substantially identically to the first magnetically free layer 118-1.

[0062] Electrodes or contacts 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 resistance R2 that is dependent on the magnetic field.

[0063] According to some embodiments, a first insulator layer (not shown) is embedded between the first magnetic reference layer 116-1 and the first magnetic free layer 118-1. A second insulator layer (not shown) is embedded between the second magnetic reference layer 116-2 and the first magnetic free layer 118-1. A third insulator layer (not shown) is embedded between the third magnetic reference layer 116-3 and the second magnetic free layer 118-2. A fourth insulator layer (not shown) is embedded between the fourth magnetic reference layer 116-4 and the second magnetic free layer 118-2. In this manner, a TMR sensor can be formed. The insulator layer is constructed to be thin enough to enable a quantum mechanical tunneling effect. The insulator layer is also referred to as a tunnel barrier. The material used for the tunnel barrier can be, for example, aluminum oxide (Al2O3) or magnesium oxide (MgO).

[0064] According to other embodiments, a first nonmagnetic conductive layer (not shown) is embedded between the first magnetic reference layer 116-1 and the first magnetic free layer 118-1. A second nonmagnetic conductive layer (not shown) is embedded between the second magnetic reference layer 116-2 and the first magnetic free layer 118-1. A third nonmagnetic conductive layer (not shown) is embedded between the third magnetic reference layer 116-3 and the second magnetic free layer 118-2. A fourth nonmagnetic conductive layer (not shown) is embedded between the fourth magnetic reference layer 116-4 and the second magnetic free layer 118-2. In this manner, a GMR sensor can be formed. The corresponding nonmagnetic conductive layers can be composed of nonmagnetic metals or alloys. These layers can achieve giant magnetoresistance by acting as a conductor for electrons whose spins are influenced by the adjacent magnetic layers. Example materials for the nonmagnetic intermediate layers in a GMR sensor are copper (Cu), gold (Au), silver (Ag), aluminum (Al), or alloys thereof.

[0065] Figure 1 Each MR sensor element 110 of the illustrated embodiment includes at least one ferromagnetic free layer 118. The ferromagnetic free layer 118 is respectively embedded between two magnetic reference systems 116 having different magnetization orientations. In some embodiments, one of the reference systems 116-2 or 116-4 includes a perpendicular magnetization (out-of-plane), and the other reference system 116-1 or 116-3 includes an in-plane magnetization (in-plane). Thus, the upper reference system 116-1 or 116-3 can have an in-plane magnetization, and the lower reference system 116-2 or 116-4 can have an out-of-plane magnetization. Reference systems 116 can each have two antiparallel coupled layers 112, 114, such as those coupled antiparallel due to the RKKY interaction. Coupling with an antiferromagnet can improve stability. For example, the different magnetization orientations of the SAF system can be achieved by laser annealing under the influence of an external magnetic field. For example, it is possible that in in-plane reference system 116-1, the uppermost layer points in the +x direction, and in adjacent in-plane reference system 116-3, the uppermost layer points in the -x direction. In other embodiments, the magnetizations of in-plane reference systems 116-1 and 116-3 may point in the +y and -y directions.

[0066] Each of the perpendicular reference systems 116-2 and 116-4 may include a synthetic antiferromagnetic perpendicular magnetization layer. Examples are multilayers, such as Co / Pt or Co / Pd multilayers. These multilayers may be coupled in antiparallel via an RKKY coupling layer, such as a Ru layer. Multiple RKKY layers may also be used.

[0067] Due to the two magnetic in-plane reference layers 116-1, 116-3 with opposite reference magnetizations, the two MR elements 110-1, 110-2 are relatively stable with respect to the external magnetic field component (B) along the x-direction.x ) have opposite transfer curves. Eddy current magnetization can be used for example for the magnetic free layers 118 - 1 and 118 - 2 , respectively. However, other magnetic free layers corresponding to the prior art can also be used.

[0068] Therefore, for B x The signal of the field can be transmitted through the difference between the resistors R1 and R2 of the two MR elements 110-1 and 110-2.

[0069] Signal x =R1-R2

[0070] The additional magnetic field component (B) in the z direction, i.e., outside the plane, is obtained. z ) changes the resistances R1 and R2 of the two MR elements 110-1 and 110-2 in the same manner and only causes the two resistances R1 and R2 to move. The difference R1-R2 remains unchanged. Therefore, Signal x It will not be changed by out-of-plane fields.

[0071] On the other hand, the magnetic field component along the z direction (B z ) can be obtained by adding two resistors R1 and R2:

[0072] Signal z =R1+R2

[0073] An additional magnetic field component (Bx, By) in the x or y direction, i.e., in the plane, increases one resistance R1 and decreases the other resistance R2 (or vice versa). Thus, the sum of the two resistances R1 and R2 remains constant with respect to the in-plane field.

[0074] The MR sensor 100 may further include an output circuit 130 coupled to the MR elements 110-1 and 110-2, the output circuit being configured to output a signal Signal proportional to the difference between the resistances R1 and R2 of the MR elements 110-1 and 110-2 for the x-component (or y-component) of the measured external magnetic field. x (or Signal y ), and outputs a signal Signal proportional to the sum of the resistances R1 and R2 of the MR elements 110-1 and 110-2 for the z component of the external magnetic field. z .

[0075] The two MR elements 110-1 and 110-2 shown can detect external magnetic fields in the x- and z-directions. If additional MR elements are implemented using an in-plane reference system in the ±y directions, the y-field can also be detected. Thus, all three magnetic field components (x, y, z) can be detected using two or more (e.g., four or six) MR elements 110, which can be implemented using the same magnetic stack.

[0076] For example, B x The field can also be read in a Wheatstone bridge configuration, where two bridge resistors (in different bridge branches) can have a resistance R1 and two bridge resistors (in different bridge branches) can have a resistance R2. Figure 2 It is schematically shown in FIG.

[0077] According to other embodiments, an MR sensor 100 having a first MR sensor element 110-1 and a second MR sensor element 110-2 can also be implemented by implementing two out-of-plane reference systems 116-2, 116-4 with antiparallel magnetizations and two in-plane reference systems 116-1, 116-3 having the same reference magnetization. Out-of-plane reference systems 116-2, 116-4 can also be reversed by the Oersted field or spin-orbit torque current of adjacent heavy metal layers.

[0078] Figure 3A The eddy current magnetized magnetic free layer 118 is shown as an example, which is sensitive to an external out-of-plane magnetic field. Figure 3A The transfer curve 302 of a vortex disk and the transfer curve 304 of a vortex ring (without a vortex core) are shown, the vortex disk and the vortex ring having a diameter of 500 nm and a thickness of 60 nm, respectively. Js = 1.0 T, A = 12 pJ / m. As in Figure 3A As can be seen in FIG, eddy current disks and eddy current rings react in principle to the orthogonal (Bz) field in the same way. This change in the Mz component can be identified by the out-of-plane reference system 116-2 or 116-4. The eddy current magnetization of the magnetically free layer 118-1 or 118-2 can have an advantage over pure in-plane magnetization in that the magnetically free layer is (more) stable with respect to the in-plane field.

[0079] Figure 3B The out-of-plane response of the eddy current disk is shown for different Bx fields (0 mT, 50 mT, 100 mT). It is confirmed that the response is in principle independent of the Bx field. A detailed analysis can be found in Table 1. Here, the linear adaptation of the transfer curve

[0080] Mz / Ms=B z a+b

[0081] This was performed for different Bx fields. It can be seen that the linear term a hardly changes depending on the Bx field. Compared to Bx=0, for a Bx field of 100 mT, the slope of the transfer curve changes by less than 0.2%.

[0082] Bx(mT) Slope a[1 / T] Change in slope a [%] 0 1.107 0.000 50 1.106 -0.090 100 1.105 -0.181

[0083] Table 1

[0084] By introducing perpendicular anisotropy in the z-direction, the sensitivity of the eddy current magnetized magnetic free layer 118-1 or 118-2 can be increased. This can be achieved by using a magnetic free layer 118-1 or 118-2 made of a material with out-of-plane anisotropy. Alternatively, a soft magnetic free layer coupled to an out-of-plane magnetized layer can be used.

[0085] Figure 4 The eddy current transfer curve is shown according to the change of the perpendicular anisotropy constant K1 (reference numeral 402 represents K1=0, reference numeral 404 represents K1=0.2MJ / m 3 , and reference numeral 406 indicates K1=0.5MJ / m 3 ). For K1 = 0.5MJ / m 3 , partially compensates for the shape anisotropy, which leads to higher sensitivity.

[0086] Figure 5 A magnetoresistive (MR) sensor 200 is shown according to further embodiments of the present disclosure.

[0087] Figure 5 The MR sensor 200 further includes 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 also be provided.

[0088] The first MR sensor element 210-1 includes two magnetically free layers embedded between first and second magnetic reference layers 116-1 and 116-2. The first MR sensor element 210-1 includes a first magnetically free layer 118-11 and a second magnetically free layer 118-12 disposed therebelow. The two magnetically free layers 118-11 and 118-12 can be composed of different materials. In other embodiments, they are composed of the same material but have different thicknesses and / or dimensions. The magnetically free layer 118-12 can be optimized for out-of-plane properties. The magnetically free layer 118-11 can be optimized for in-plane properties. The two layers 118-11 and 118-12 can be exchange-decoupled. In the illustrated design, a first conductive layer 502-1 (e.g., made of Cu) is disposed between the first magnetically free layer 118-11 and the second magnetically free layer 118-12. In other designs, this layer can also be exchange-coupled and composed of a ferromagnetic or antiferromagnetic material.

[0089] The second MR sensor element 210-2 includes a third magnetically free layer 118-21 and a fourth magnetically free layer 118-22 disposed thereunder. The two layers 118-21, 118-22 can be composed of different materials. In other embodiments, they are composed of the same material but have different thicknesses or dimensions. The magnetically free layer 118-22 can be optimized for out-of-plane properties. The magnetically free layer 118-21 can be optimized for in-plane properties. In the illustrated design, a second conductive layer 502-2 (e.g., made of Cu) is disposed between the third magnetically free layer 118-21 and the fourth magnetically free layer 118-22. In other designs, this layer can also be exchange coupled and composed of a ferromagnetic material or an antiferromagnetic material.

[0090] The first magnetic reference layer 116-1 arranged above the first magnetic free layer 118-11 in the first MR sensor element 210-1 may include a ferromagnetic layer that may have high coercivity (the ferromagnetic layer maintains its magnetic orientation in an external magnetic field). This can be achieved, for example, by coupling with an antiferromagnet. In a design according to the present invention, an antiferromagnet can be implemented above the reference layer 116-1. The first magnetic reference layer 116-1 can serve as a first magnetic reference layer, and the orientation of the first magnetic free layer 118-11 is compared with the first magnetic reference layer. Figure 5 In the example shown, 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 should be understood that the first reference magnetization can also point in another direction (e.g., the +y direction).

[0091] The second magnetic reference layer 116-2 disposed below the second magnetically free layer 118-12 in the first MR sensor element 210-1 may include a ferromagnetic layer that may have high coercivity. This may be achieved, for example, by coupling with an antiferromagnet. In a design according to the present invention, an antiferromagnet may be implemented above the reference layer 116-1. The second magnetic reference layer 116-2 may serve as a second magnetic reference layer, with the orientation of the second magnetically free layer 118-12 being compared to the second magnetic reference layer. Figure 5 In the example shown, a SAF structure is also used for the second magnetic reference layer 116 - 2 .

[0092] In the example shown, the second reference magnetization of the second magnetic reference layer 116 - 2 is an out-of-plane magnetization (eg, in the +z direction).

[0093] Electrodes or contacts 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 resistance R1 that is dependent on the magnetic field.

[0094] The third magnetic reference layer 116-3 disposed above the third magnetic free layer 118-12 in the second MR sensor element 210-2 may include a ferromagnetic layer that may have high coercivity. The third magnetic reference layer 116-3 may serve as a first magnetic reference layer, with the orientation of the third magnetic free layer 118-12 being compared to the third magnetic reference layer. Figure 5 In the example shown, a SAF structure is used for the third magnetic reference layer 116 - 3 .

[0095] In the example shown, the third reference magnetization of third magnetic reference layer 116-3 is an in-plane magnetization opposite to the first reference magnetization of first magnetic reference layer 116-1 (e.g., in the -x direction). It should be understood that the third reference magnetization can also point in another direction (e.g., in the -y direction). Here, antiferromagnets can also be used to improve stability.

[0096] The fourth magnetic reference layer 116-4 disposed below the fourth magnetic free layer 118-22 in the second MR sensor element 210-2 may include a ferromagnetic layer that may have high coercivity. The fourth magnetic reference layer 116-4 may serve as a second magnetic reference layer, with the orientation of the fourth magnetic free layer 118-22 being compared to the fourth magnetic reference layer. Figure 5 In the example shown, the SAF structure is also used for the fourth magnetic reference layer 116 - 4 .

[0097] In the example shown, the fourth reference magnetization of the fourth magnetic reference layer 116 - 4 is an out-of-plane magnetization (eg, in the −z direction) that is opposite the second reference magnetization of the second magnetic reference layer 116 - 2 .

[0098] Electrodes or contacts 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 resistance R2 that is dependent on the magnetic field.

[0099] 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 magnetic free layer 118-11. A second insulator layer (not shown) is embedded between the second magnetic reference layer 116-2 and the second magnetic free layer 118-12. A third insulator layer (not shown) is embedded between the third magnetic reference layer 116-3 and the third magnetic free layer 118-21. A fourth insulator layer (not shown) is embedded between the fourth magnetic reference layer 116-4 and the fourth magnetic free layer 118-22. In this manner, a TMR sensor can be formed.

[0100] According to other embodiments, a first nonmagnetic conductive layer (not shown) is embedded between the first magnetic reference layer 116-1 and the first magnetic free layer 118-11. A second nonmagnetic conductive layer (not shown) is embedded between the second magnetic reference layer 116-2 and the second magnetic free layer 118-12. A third nonmagnetic conductive layer (not shown) is embedded between the third magnetic reference layer 116-3 and the third magnetic free layer 118-21. A fourth nonmagnetic conductive layer (not shown) is embedded between the fourth magnetic reference layer 116-4 and the fourth magnetic free layer 118-22. In this manner, a GMR sensor can be formed.

[0101] In addition, according to Figure 5 The MR sensor 200 may further include an output circuit 130 coupled to the MR elements 210-1 and 210-2, the output circuit being configured to output a signal Signal proportional to the difference between the resistances R1 and R2 of the MR elements 210-1 and 210-2 for the x-component (or y-component) of the measured external magnetic field. x (or Signal y ), and outputs a signal Signal proportional to the sum of the resistances R1 and R2 of the MR elements 210-1 and 210-2 for the z component of the external magnetic field. z .

[0102] exist Figure 6 In the embodiment of the present invention, an exemplary magnetic free layer 118-12 or 118-22 optimized for out-of-plane properties is compared with a free layer with eddy current magnetization. The out-of-plane optimized magnetic free layer 118-12 or 118-22 can be composed 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 magnetic free layer 118-12 or 118-22 (which can also be a SAF) is linearly related to the Hz field. In order to improve the sensitivity of the free SAF layer 118-12 or 118-22, the free SAF layer can, for example, utilize a perpendicular anisotropy K1 = 0.28 MJ / m 3 accomplish.

[0103] Due to SAF coupling, the magnetic free layer 118 - 12 or 118 - 22 is also insensitive to the Bx field, as shown in FIG. Figure 6 Table 2 shows that, compared with Bx=0, when a Bx field of 50 mT (7% of the linear range) is applied, the slope of the transfer function of the free SAF layer changes by 0.6%.

[0104] Bx(mT) Slope a[1 / T] Change in slope a [%] 0 1.465 0.000 50 1.4557 -0.635

[0105] Table 2

[0106] 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 in-plane free layers.

[0107] The in-plane optimized magnetic free layer 118 - 11 or 118 - 12 may be a layer with a vortex state (eg, a vortex disk) or an in-plane free layer with a synthetic antiferromagnetic coupling having shape anisotropy.

[0108] As an alternative to a thick magnetic free vortex layer for combined in-plane and out-of-plane detection, a very thin free layer with perpendicular anisotropy in the superparamagnetic state between the two reference systems 116 - 1 , 116 - 2 can be used.

[0109] Figure 7 Further conceivable exemplary embodiments of MR sensors are shown. Figure 7 A possible MR sensor 700 is shown that includes a first MR sensor element 710 - 1 and a second MR sensor element 710 - 2 .

[0110] The first MR sensor element 710-1 has a first magnetic reference layer 716-1 with a first reference magnetization. The first reference magnetization is directed outward from the plane of the reference layer 716-1 at a first angle. The first angle can be, for example, in the range of 20° to 70°, preferably 45°. The first MR sensor element 710-1 also has a first magnetically free layer 118-1 (e.g., having an eddy current 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 conductive layer (GMR).

[0111] Electrodes or contacts 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 resistance R1 that is dependent on the magnetic field.

[0112] The second MR sensor element 710-2 has a second magnetic reference layer 716-2 with a second reference magnetization that is different from (e.g., perpendicular to) the first reference magnetization. The second reference magnetization is directed outward from the plane of the reference layer 716-2 at a second angle. The second angle can be, for example, in the range of 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., having an eddy current 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 conductive layer (GMR).

[0113] Electrodes or contacts 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 resistance R2 that is dependent on the magnetic field.

[0114] The MR sensor 700 may include an output circuit 130 coupled to the MR elements 710-1 and 710-2. The output circuit 130 is configured to output a signal Signal proportional to the difference between the resistances R1 and R2 of the MR elements 710-1 and 710-2 for the x-component (or y-component) of the external magnetic field being measured. x (or Signal y ), and outputs a signal Signal proportional to the sum of the resistances R1 and R2 of the MR elements 710-1 and 710-2 for the z component of the external magnetic field. z .

[0115] Orienting the reference magnetization in the reference layer 716 out of plane at an angle of, for example, 45° can present certain technical challenges. Orienting the magnetization at intermediate angles relative to the plane (e.g., 45°) may require a specific balance of magnetic anisotropy, both in-plane and perpendicular to the plane. Achieving partial out-of-plane orientation may involve complex layer structures or specialized material combinations with anisotropy both in-plane and out-of-plane. This can be modified during separation by external fields or by subsequent thermal or mechanical treatments.

[0116] The aspects and features described in conjunction with a specific example in the preceding examples may also be combined with one or more examples in other examples to replace the same or similar features of the other examples or to additionally introduce the features into the other examples.

[0117] It is further understood that the disclosure of multiple steps, processes, operations, or functions disclosed in the specification or claims should not be designed to be mandatory in the order described, unless this is explicitly stated in individual cases or is mandatory for technical reasons. Therefore, the above description does not limit the execution of multiple steps or functions to a specific order. In addition, in other examples, a single step, a single function, a single process, or a single operation can include and / or be decomposed into multiple sub-steps, sub-functions, sub-processes, or sub-operations.

[0118] If aspects were described in the preceding paragraphs in conjunction with an apparatus or system, these aspects should also be understood as descriptions of corresponding methods. Here, a block, apparatus, or functional aspect of an apparatus or system may, for example, correspond to features of a corresponding method, such as method steps. Therefore, aspects described in conjunction with a method should also be understood as descriptions of corresponding blocks, corresponding elements, characteristics, or functional features of the corresponding apparatus or system.

[0119] The following claims are hereby incorporated into the detailed description, where each claim may serve as a separate example. It should also be noted that although dependent claims are referred to in a claim as a specific combination with one or more other claims, other examples may also include combinations of dependent claims with the subject matter of any other dependent or independent claim. Therefore, such combinations are expressly recommended unless it is stated in individual cases that a specific combination is not intended. In addition, features of a claim should also be included with respect to each other independent claim, even when the claim is not directly defined as dependent on that other independent claim.

Claims

1. A magnetoresistive sensor (100; 110), comprising: a first magnetic reference layer (116-1); a second magnetic reference layer (116-2); and At least one magnetic free layer (118-1) is embedded between the first magnetic reference layer and the second magnetic reference layer.

2. The 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. The 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. The magnetoresistive sensor (100; 110) according to any one of the preceding claims, comprising: A first magnetic free layer (118-11) and a second magnetic free layer (118-12) are embedded between the first reference layer (116-1) and the second reference layer (116-2).

5. The magnetoresistive sensor (100; 110) according to claim 4, wherein A conductive layer is disposed between the first magnetic free layer (118-11) and the second magnetic free layer (118-12).

6. The magnetoresistive sensor (100; 110) according to claim 4 or 5, wherein: The first magnetically free layer (118-11) has an in-plane eddy current magnetization in the absence of an external magnetic field, and the second magnetically free layer (118-12) has a synthetic antiferromagnet with an out-of-plane magnetization in the absence of an external magnetic field.

7. The magnetoresistive sensor (100; 110) according to any one of the preceding claims, wherein The first magnetic reference layer (116-1) and / or the second magnetic reference layer (116-2) respectively include a plurality of ferromagnetic layers and / or antiferromagnetic layers.

8. The magnetoresistive sensor (100; 110) according to any one of the preceding claims, wherein A first insulator layer is embedded between the first magnetic reference layer (116-1) and the at least one magnetic free layer (118-1), and a second insulator layer is embedded between the second magnetic reference layer (116-2) and the at least one magnetic free layer (118-1).

9. The magnetoresistive sensor (100; 110) according to any one of claims 1 to 8, wherein: A first nonmagnetic conductive layer is embedded between the first magnetic reference layer (116-1) and the at least one magnetic free layer (118-1), and a second nonmagnetic conductive layer is embedded between the second magnetic reference layer (116-2) and the at least one magnetic free layer (118-1).

10. The magnetoresistive sensor (100; 110) according to any one of the preceding claims, wherein The at least one magnetically free layer (118-1) has eddy current magnetization.

11. A magnetoresistive sensor (100; 200), comprising: A first magnetoresistive sensor element (110-1) having a first magnetic reference layer (116-1) having a first reference magnetization; a second magnetic reference layer (116-2) having a second reference magnetization; wherein the first reference magnetization and the second reference magnetization are perpendicular to each other; and at least one first magnetic free layer (118-1) embedded between the first magnetic reference layer and the second magnetic reference layer; and The second magnetoresistive sensor element (110-2) has a third magnetic reference layer (116-3) having a third reference magnetization; a fourth magnetic reference layer (116-4) having 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 magnetic free layer (118-2) is embedded between the first magnetic reference layer and the second magnetic reference layer.

12. The magnetoresistive sensor (100; 200) according to claim 11, wherein The first reference magnetization and the third reference magnetization are each an in-plane reference magnetization, and the second reference magnetization and the fourth reference magnetization are each an out-of-plane reference magnetization.

13. The magnetoresistive sensor (100; 200) according to claim 11 or 12, wherein: The first magnetic free layer (118-1) and the second magnetic free layer (118-2) each have eddy current magnetization.

14. The magnetoresistive sensor (100; 200) according to any one of claims 11 to 13, comprising: an upper magnetic free layer (118-11) and a lower magnetic free layer (118-12) embedded between the first magnetic reference layer and the second magnetic reference layer; and An upper magnetic free layer (118-21) and a lower magnetic free layer (118-22) are embedded between the third magnetic reference layer and the fourth magnetic reference layer.

15. The magnetoresistive sensor (100; 200) according to claim 14, wherein Conductive layers are respectively arranged between the upper magnetic free layer (118-11; 118-21) and the lower magnetic free layer (118-12; 118-22).

16. The magnetoresistive sensor (100; 200) according to claim 14 or 15, wherein The upper magnetic free layer (118-11; 118-21) has an in-plane eddy current magnetization when the external magnetic field disappears, and the lower magnetic free layer (118-12; 118-22) has a synthetic antiferromagnet with an in-plane magnetization when the external magnetic field disappears.

17. The magnetoresistive sensor (100; 200) according to any one of claims 11 to 16, wherein: The magnetic reference layers each include a plurality of ferromagnetic layers and / or antiferromagnetic layers.

18. The magnetoresistive sensor (100; 200) according to any one of claims 11 to 17 further includes an output circuit (130), which is configured to output a signal that is proportional to the difference in resistance between the first magnetoresistive sensor element (110-1) and the second magnetoresistive sensor element (110-2) for a first magnetic field component of the measured external magnetic field, and to output a signal that is proportional to the sum of the resistances of the first magnetoresistive sensor element (110-1) and the second magnetoresistive sensor element (110-2) for a second magnetic field component of the external magnetic field.

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