Magnetoresistance element with high out-of-plane sensitivity

Abstract

The present disclosure relates to a magnetoresistive element comprising a reference layer (21) having a reference magnetization (210) oriented out-of-plane, a sense layer (23) having a sense magnetization (230) that has a stable vortex morphology in the presence of an external magnetic field (60) and that is reversibly movable in an out-of-plane direction relative to the reference magnetization when the external magnetic field (60) is changed in an out-of-plane direction, and a tunnel barrier layer (22) between the reference layer and the sense layer. The sense layer has a thickness of less than 200 nm. The sense layer (23) has a sense magnetization of 300 emu / cm. 3 and 1400 emu / cm 3 and the sense layer 23 is 1 kOe (79.6×10 3 The present disclosure further relates to a magnetoresistive sensor comprising a plurality of such magnetoresistive elements.

Description

[Technical field]

[0001]

[0001] The present invention relates to a magnetoresistive element for a magnetic sensor designed to sense an external magnetic field. More particularly, the present invention relates to a magnetoresistive element having a sense layer and high out-of-plane sensitivity. The present invention further relates to a magnetoresistive element for measuring an external magnetic field along an axis substantially perpendicular to the plane of the sense layer. [Background technology]

[0002] A magnetoresistive element typically comprises a reference layer having a reference magnetization and a sense layer having a free sense magnetization, with a tunnel barrier layer sandwiched between the reference layer 21 and the sense layer.

[0003]

[0003] Such magnetoresistive elements can be used to sense the out-of-plane component of an external magnetic field. For a magnetoresistive element to sense an external magnetic field with high out-of-plane sensitivity, it must have a high tunneling magnetoresistance (TMR) value, a small size (diameter), a thick sense layer, and a low sense magnetization.

[0004]

[0004] Implementing thick film sense layers (>100 nm) introduces challenges in the manufacturing process of the magnetoresistive elements. For example, the manufacturing process may require lengthy etching, redeposition, shortening, etc. These challenges can be at least partially overcome by modifying the layout of the sensor with several magnetoresistive elements. However, this leads to a reduction in the magnetoresistive element density per sensor area.

[0005]

[0005] Applicant's patent application EP20315489.3 (unpublished) discloses a magnetoresistive element comprising a reference layer with a fixed reference magnetization, a sense layer with a free sense magnetization, and a tunnel barrier layer. The magnetoresistive element is configured to measure an external magnetic field oriented substantially perpendicular to the plane of the layer. The reference magnetization is oriented substantially perpendicular to the plane of the reference layer. The sense magnetization has a spiral morphology in the absence of an external magnetic field. The spiral morphology has a magnetization direction of the spiral core along an out-of-plane axis substantially parallel to the plane of the sense layer and substantially perpendicular to the plane of the sense layer. The thickness of the sense layer is greater than 50 nm.

[0006]

[0006] The EP2320489A1 document discloses a spin valve element capable of multi-value recording, which comprises a pair of ferromagnetic layers having different coercivity, the pair of ferromagnetic layers sandwiching an insulating or non-magnetic layer, the ferromagnetic layers having a small coercivity, a substantially circular in-plane profile and a plurality of island-shaped non-magnetic portions.

[0007]

[0007] WO2013180277 discloses an oscillator with the function of enabling high frequency oscillation, high Q value, and high thermal stability by using a magnetic vortex structure and interlayer exchange coupling. The oscillator includes a pinned layer including a magnetic material with fixed magnetization having a magnetic vortex structure magnetized perpendicularly at the center, a non-magnetic layer including a non-magnetic material stacked on the pinned layer, a free layer with perpendicular magnetization stacked on the non-magnetic layer and rotatably moving in the surface direction (the free layer includes a ferromagnetic material having a magnetic vortex structure magnetized perpendicularly at the center and having a circular or regular polygonal surface configuration), and a current supply unit for sending a current through the layer.

[0008]

[0008] The document EP3862769 discloses a magnetoresistive sensor element comprising a reference layer with a pinned reference magnetization, a sense layer with a free sense magnetization with a stable vortex-like configuration reversibly movable in response to a measured external magnetic field, and a tunnel barrier layer. The sense layer comprises a first ferromagnetic sensing portion in contact with the tunnel barrier layer and a second ferromagnetic sensing portion in contact with the first ferromagnetic sensing portion. The second ferromagnetic sensing portion contains a dilution element in a proportion such that the temperature dependence of the magnetic susceptibility of the sense layer substantially compensates for the temperature dependence of the tunnel magnetoresistance of the magnetoresistive sensor element. Summary of the Invention [Problem to be solved by the invention]

[0009]

[0009] It is an object of the present disclosure to improve the sensitivity of a magnetoresistive element by introducing a perpendicular magnetic anisotropy (PMA) across the sense layer of the magnetoresistive element having a vortex morphology. [Means for solving the problem]

[0010]

[0010] The present disclosure relates to a magnetoresistive element comprising a reference layer having a reference magnetization oriented out-of-plane, a sense layer having a sense magnetization with a stable vortex-like morphology in the presence of an external magnetic field, the sense magnetization being reversibly movable in the out-of-plane direction relative to the reference magnetization when the external magnetic field is changed in the out-of-plane direction, and a tunnel barrier layer between the reference layer and the sense layer. The sense layer has a thickness of less than 200 nm. The sense layer has a sense magnetization of 300 emu / cm 3 and 1400 emu / cm 3 and the sense layer is 1 kOe (79.6 × 10 3 The magnetic material includes a ferromagnetic material configured to have a perpendicular magnetic anisotropy field exceeding 100 A / m.

[0011] The vortex morphology is maintained in the presence of an external magnetic field of any direction with an amplitude of 2.5 kOe or greater.

[0012] The magnetoresistive element can be used to measure an external magnetic field oriented in a direction perpendicular to the out-of-plane direction, ie, substantially perpendicular to the plane of the sense layer.

[0013]

[0013] The present disclosure further relates to a magnetoresistive sensor comprising a plurality of magnetoresistive elements as described above. The magnetoresistive sensor may be arranged in a Wheatstone circuit. The magnetoresistive sensor has an out-of-plane sensitivity of more than 1 mV / V / mT.

[0014] The disclosed magnetoresistive element overcomes the drawbacks and limitations of known magnetoresistive elements while maintaining a high level of out-of-plane sensitivity.

[0015]

[0015] These and other advantages will become apparent from the following description.

[0016]

[0016] Exemplary embodiments of the present invention are disclosed herein and illustrated by the following drawings. [Brief description of the drawings]

[0017] [Figure 1] FIG. 2 illustrates a magnetoresistive element with a sense layer according to one embodiment. [Diagram 2] FIG. 2 illustrates a magnetoresistive sensor comprising multiple magnetoresistive elements according to one embodiment. [Diagram 3] FIG. 13 illustrates the change in sense magnetization as a function of magnetic field for a 84 nm thick sense layer. [Figure 4] FIG. 13 illustrates the change in sense magnetization as a function of magnetic field for a 20 nm thick sense layer. [Diagram 5] FIG. 2 is a diagram of a portion of a sense layer according to one embodiment. [Figure 6] FIG. 2 illustrates a portion of a sense layer with an oxide insert according to one embodiment. [Figure 7] FIG. 13 is a diagram of a portion of a sense layer with an oxide insert according to another embodiment. [Figure 8] FIG. 2 illustrates a sense layer according to another embodiment. [Figure 9] FIG. 2 illustrates out-of-plane magnetization loops for several configurations of the sense layer. [Figure 10] FIG. 10 shows the results of fitting the out-of-plane magnetization loops of FIG. 9 to determine the perpendicular magnetic anisotropy field. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018]

[0017] Figure 1 illustrates a magnetoresistive element 2 according to one embodiment. The magnetoresistive element 2 comprises a reference layer 21 having a reference magnetization 210 and a sense layer 23 having a free sense magnetization 230. The magnetoresistive element 2 further comprises a tunnel barrier layer 22 between the reference layer 21 and the sense layer 23. The sense magnetization 230 can be freely oriented under an external magnetic field 60 according to the direction of the external magnetic field 60, while the reference magnetization 210 is substantially undisturbed. Thus, the external magnetic field 60 can be sensed by measuring the resistance of the magnetoresistive sensor element 2. The magnetoresistive element 2 may further comprise optional cap layers 24, 25 adjacent to the sense layer 23 and the reference layer 21, respectively.

[0019] The sense magnetization 230 has a stable vortex morphology that is stable in the presence of the external magnetic field 60. In one embodiment, the sense magnetization 230 has a magnetic field strength of 2.5 kOe (199×10 3 The magnetoresistive element 2 has a stable vortex morphology that is stable in the presence of an external magnetic field 60 having an amplitude of 100 .ANG. / m or more. This vortex morphology provides linear, hysteresis-free behavior in the region of large strength of the external magnetic field 60 relative to the packaging size of the magnetoresistive element 2 and the thickness of the sense layer 23.

[0020]

[0019] The resistance of the magnetoresistive element 2 is determined by the averaged component of the sense magnetization 230 in a direction substantially perpendicular to the plane of the sense layer 23 (along the direction indicated by "z" in FIG. 1) with respect to the orientation of the reference magnetization 210 when the external magnetic field 60 varies in an out-of-plane direction. Sensing of the external magnetic field 60 can be performed by measuring the output voltage when a measurement current 31 flows through the magnetoresistive element 2. Thus, the vortex topology is beneficial for 1D magnetic sensor applications, especially for sensing an external magnetic field 60 oriented out-of-plane.

[0021] In one embodiment, the reference magnetization 210 is oriented out-of-plane, ie, perpendicular to the reference layer 21 (z-direction).

[0022]

[0021] The reference layer 21 may include or be formed of a ferromagnetic alloy, such as CoFe, NiFe, or CoFeB. The reference layer 21 may include one or more ferromagnetic layers or synthetic antiferromagnets (SAFs). The reference layer 21 may have a thickness between 2 nm and 4 nm, and preferably has a thickness of about 4 nm.

[0023]

[0022] As shown in Fig. 1, the reference layer 21 may have a synthetic anti-ferromagnet (SAF) configuration. For example, the reference layer 21 may include a first reference layer 211 in contact with the tunnel barrier layer 22, a coupling layer 212, and a second reference layer 13, in that order. The first reference layer 211 (soft reference layer) may include or be formed of a soft ferromagnetic material, such as CoFe or CoFeB. The second reference layer 213 may include or be formed of a hard ferromagnetic material (hard reference layer). The hard ferromagnetic material may include a Co / Pt multilayer. The coupling layer 212 may be configured to achieve RKKY coupling. Each of the first and second reference layers 211, 213 has an out-of-plane reference magnetization 210, where the stability of the reference magnetization 210 is achieved by coercivity and RKKY coupling.

[0024] For example, the reference layer 21 may include (Pt / Co)*n / Ru / (Pt / Co)*m / CoFeB, where the Pt / Co multilayer is stacked n times and the Pt / Co multilayer is stacked m times, where n and m can vary between 1 and 20.

[0025]

[0024] The tunnel barrier 22 may include an insulating material. Suitable insulating materials include oxides such as aluminum oxide (e.g., Al2O3) and magnesium oxide (e.g., MgO). The thickness of the tunnel barrier layer 22 may be in the nanometer range, such as from about 1 nm to about 3 nm. In a preferred embodiment, the tunnel barrier layer 22 is MgO, for example, deposited by sputtering an MgO target, or by depositing one or more Mg layers and then oxidizing the one or more Mg layers using known radical oxidation (ROX) or natural oxidation (NOX) processes. The interface of the MgO layer with a magnetic layer that is CoFeB, for example, provides a higher interfacial perpendicular anisotropy and a greater strength of PMA at the magnetic layer than interfaces with other metal oxides.

[0026] In one embodiment, the sense layer 23 has a thickness of less than 200 nm, for example between 5 nm and 200 nm. Preferably, the sense layer 23 has a thickness between 5 nm and 50 nm, between 5 nm and 100 nm, or between 3 nm and 30 nm.

[0027] The sense layer (23) has a sense magnetization 230 of 300 emu / cm 3 From 1400 emu / cm 3 and the sense layer 23 is between 1 kOe (79.6×10 3 A / m) PMA The sense layer 23 includes a ferromagnetic material configured to have a PMA. The sense layer 23 so configured allows for compensation of the demagnetizing field present in thin sense layers (<50 nm) and improves the sensitivity S of the magnetoresistive element 2 relative to sense layers without a PMA.

[0028] In one embodiment, the sense layer 23 is made of a soft ferromagnetic material and a perpendicular magnetic anisotropy field H PMA and a strengthening material configured to enhance the PMA in the sense layer 23. For example, the soft ferromagnetic material may include a NiFe, CoFe, or CoFeB alloy. The strengthening material enhances the PMA in the sense layer 23 and improves the out-of-plane sensitivity S of the magnetoresistive element 2. The strengthening material allows for an improvement in the out-of-plane sensitivity S without increasing the thickness of the sense layer 23.

[0029]

[0028] The magnetoresistive sensor may comprise multiple magnetoresistive elements 2 to sense a 1D external magnetic field 60. In one embodiment shown in FIG. 2, the magnetoresistive sensor 20 is arranged in a Wheatstone full bridge circuit. More specifically, the full bridge circuit comprises two series-connected magnetoresistive elements 2a, 2b, which are connected in parallel with two other series-connected magnetoresistive elements 2c, 2d. The reference magnetization 210 of the two upper magnetoresistive elements 2a, 2c may be oriented in a substantially opposite direction to one of the two lower magnetoresistive elements 2b, 2d. The magnetoresistive sensor 20 forms a voltage divider. In the presence of an external magnetic field 60, an output voltage V out can be measured between the magnetoresistance elements 2a, 2b of the first half-bridge and between the magnetoresistance elements 2c, 2d of the second half-bridge. Other configurations of TMR sensing elements, such as half-bridges, are also possible.

[0030] The sense magnetization can be characterized by its magnetic susceptibility χ, which corresponds to the slope of the linear region of the magnetization curve as shown in the following equation: χ=∂M / ∂Bz (1) where M is the unitless magnetization and Bz is the z-component of the external magnetic flux in Tesla (T).

[0031] For a Wheatstone bridge layout (such as that shown in FIG. 2), the sensitivity S of the magnetoresistive element 2 can be derived as follows: S = TMR / (2 + TMR)χ (2)

[0032]

[0031] Figure 3 shows the variation of the sense magnetization 230 (mz in Figure 3) as a function of a magnetic field Bz in the z or out-of-plane direction. Here, the sense layer 23 has a thickness of 84 nm and a perpendicular magnetic anisotropy field H PMA The ferromagnetic material includes a ferromagnetic material having a H PMA =4kOe(318.4×10 3 A / m) from 1mV / V / mT, H PMA =2(159.2×10 3 A / m) and H PMA 2 in response to a change in the external magnetic field 60 in the out-of-plane direction. out This represents a change in

[0033] FIG. 4 shows a 20 nm thick GaN film with a capacitance of 0 to 3 kOe (0 to 238.8×10 3 The perpendicular magnetic anisotropy field H varies in the range of PMA 4 and 5 show the change in the sense magnetization 230 according to the magnetic field Bz for the sense layer 23 including a ferromagnetic material having the following properties: Here, the out-of-plane sensitivity S changes in the range of 0.43 mV / V / mT to 0.8 mV / V / mT, respectively.

[0034] In both FIG. 3 and FIG. 4, the sensitivity S is determined using equation (3) for the full-bridge sensitivity, assuming the TMR ratio is 100%; in FIG. -1 The sensitivity S of 1mV / V / mT for the magnetic susceptibility is 2.7T -1 The sensitivity S of 0.9mV / V / mT for the magnetic susceptibility of 1.9T -1 In Fig. 4, the sensitivity S of 0.63 mV / V / mT is obtained for the magnetic susceptibility of 2.4T. -1 The sensitivity S of 0.8mV / V / mT for the magnetic susceptibility of 1.9T -1 The sensitivity S of 0.63mV / V / mT for the magnetic susceptibility of 1.5T -1 The sensitivity S of 0.5mV / V / mT for the magnetic susceptibility of 1.3T-1 It was designed to obtain a sensitivity S of 0.43 mV / V / mT for a magnetic susceptibility of 0.

[0035]

[0034] In a thin film sense layer 23, the demagnetizing field suppresses the out-of-plane component of the magnetization, thus reducing the sensitivity S. Also, the remanence of the sense magnetization 230 becomes smaller for a thin film sense layer 23 as the demagnetizing field becomes larger. In a thick film sense layer 23, the demagnetizing field is smaller and the sensitivity S is larger. Furthermore, in a thin film sense layer 23, the introduction of PMA allows the demagnetizing field to be compensated, resulting in a similar sensitivity level compared to that obtained with a thick film sense layer without PMA.

[0036] 5 shows a diagram of a portion of a sense layer 23 including a first portion 231 that includes or is formed from a soft ferromagnetic material and a second portion 232 that includes or is formed from a reinforcement material. The soft ferromagnetic material may include NiFe, CoFe, or CoFeB alloys.

[0037]

[0036] Preferably, the magnetoresistive element 2 includes an interface layer 26 (see Figure 1) between the tunnel barrier layer 22 and the sense layer 23, which includes or is formed from CoFeB, to achieve a high TMR ratio (greater than 100%).

[0038] In one embodiment, the reinforcing material is (Co / Pt) n , (Co / Pd) n , (Co / Au) n , (Co / Fe) n , (CoCr / Pt) n , (NiFe / Cu) n , or (Co / Cu) n where n is the number of multilayers and n is between about 10 and 100. The reinforcement material can comprise other laminate stacks exhibiting unique PMA and n is between 1 and 10. The above laminates can be any of the following, depending on which of the metal layers is deposited first: (Pt / Co) n , (Pd / Co)n , (Au / Co) n , (Fe / Co) n , (Pt / CoCr) n , (Cu / NiFe) n , or (Cu / Co) n It should be noted that the laminate can also be represented by: In one embodiment, the laminate is NiFe / (laminate / NiFe) n where the number n may be determined by the desired total thickness of the sense layer 23 and the intercalation concentration in NiFe.

[0039] Typically, the Co or Co alloy layers in the laminate have a thickness between 0.05 nm and 0.5 nm, while the Pd, Pt, Cu, or Au layers have a thickness between 0.2 nm and 1 nm.

[0040] Typically, as the number of stacks "n" increases, the PMA in the stack increases. However, (Co / Ni) n The magnetoresistance (MR) ratio of deposited layers such as CoFeB is generally less than that observed for CoFe or CoFeB layers. In the present magnetoresistance element 2, a TMR ratio of 100% or more can be obtained by including the interface layer 26.

[0041] In another embodiment, the reinforcing material comprises an oxide insert 232 within the soft ferromagnetic material.

[0042] In one embodiment, the oxide insert includes a continuous layer 232 or multiple continuous layers 232 (see FIG. 6). The continuous layer 232 is in a first portion 231 that includes or is formed from a soft ferromagnetic material.

[0043] The second portion 232 including the reinforcing material has a thickness between 0.1 nm and 5 nm.

[0044] In another embodiment shown in FIG. 7, the oxide insert comprises a plurality of clusters 232.

[0045]

[0044] The oxidation state and thickness of the oxide insert layer, or the size of the oxide insert clusters, can be controlled to provide a smaller resistance-area (RA) product than the oxide in the tunnel barrier layer 33 to minimize the reduction in the MR ratio of the magnetoresistive element 2.

[0046]

[0045] Preferably, the oxide insert comprises MgO, however, other oxides may be considered, including SiOx, SrTiOx, BaTiOx, CaTiOx, LaAlOx, MnOx, VOx, AlOx, TiOx, MgTaOx, and HfOx.

[0047] In another embodiment shown in FIG. 8, the sense layer 23 is (NiFe / Ni) n , (Ni / Co) n , or (NiFe / Co) n In FIG. 8, the bilayer (A / B) n The laminated structures including these are designated by the reference numerals 233 and 234, respectively (eg, layer A is 233 and layer B is 234).

[0048]

[0047] One or more of the deposited layers may be a Co-based alloy such as CoFe or CoFeB instead of Co, or a Ni-based alloy such as NiCo, NiFe, or NiFeB instead of Ni. Preferably, the Co-based alloy is Co-rich, where the Co content is >50 atomic %, and the Ni-based alloy is Ni-rich, where the Ni content is >50 atomic %. Thus, (CoFe / Ni) n , (CoFeB / Ni) n , (Co / NiFe) n , (Co / NiFeB) n , and (NiCo / Co) n serves as a substitute for the sense layer 23.

[0049] In yet another embodiment, the ferromagnetic material comprises a Heusler alloy. 3 to 400 emu / cm 3 to 1 kOe (79.6×10 3 A / m) PMA This allows the sense layer 23 to have a thickness between 5 nm and 20 nm so as to have

[0050] In one embodiment, the Heusler alloy may include a Mn-containing alloy. For example, the Heusler alloy may include a NiMnGa, CoMnGa, FeMnGa, CoFeSi, CoMnSi, NiMnSb, CoMnSb, or CoMnAl alloy.

[0051] In another embodiment, the Heusler alloy may include Co2FeAl, MnAs, MnSb, CoTb, NdCo5, or SmCo5 alloys.

[0052] FIG. 9 shows out-of-plane magnetization loops for several configurations of the sense layer 23 including the following stack structures: NiFe10 / [Co0.3 / Pt0.4 / Co0.3] / NiFe10, 1 time; NiFe5 / [Co0.3 / Pt0.4 / Co0.3] / NiFe5, stacked three times; NiFe2.5 / [Co0.3 / Pt0.4 / Co0.3] / NiFe2.5, 7 stacks; NiFe2 / [Co0.3 / Pt0.4 / Co0.3] / NiFe2, 9 stacks; NiFe1 / [Co0.3 / Pt0.4 / Co0.3] / NiFe1, 19 stackings.

[0053] Also shown is the out-of-plane magnetization loop for the sense layer 23 which includes a 20 nm layer of pure NiFe.

[0054] FIG. 10 shows the perpendicular magnetic anisotropy field H PMA Figure 10 shows the fitting results of the out-of-plane magnetization loops in Figure 9 using a macrospin model to determine the perpendicular magnetic anisotropy field H PMA is positive for stacked structures containing 10 or more stacks of Co0.3 / Pt0.4 / Co0.3. The perpendicular magnetic anisotropy field H PMA The value of is strong enough to provide large out-of-plane sensitivity as shown in the simulation of FIG. 4 without the need for a thick sense layer 23 (eg, the thickness of the sense layer 23 can be less than 100 nm).

[0055]

[0054] Low magnetization and high perpendicular magnetic anisotropy field H PMA (For example, about 1 kOe (79.6 × 10 3 A / m), or 1 to 3 kOe (79.6×10 3 and 238.7 × 10 3 A / m) perpendicular magnetic anisotropy field H PMA Calculations have been shown to show that a magnetoresistance element 2 having a sense layer 23 with a .lambda..sub.1 and .lambda..sub.2 allows for a high level of sensitivity S (e.g., an out-of-plane sensitivity S of greater than 1 mV / V / mT) to be obtained, with the sense layer 23 being 50 nm or less thick. This magnetoresistance element 2 is therefore simpler to manufacture, since no manufacturing process modifications are required when depositing a thick film sense layer. Furthermore, it allows for a more compact sensor layout to be realized. [Explanation of symbols]

[0056] 2, 2a to 2d Magnetoresistance element 20 Magnetoresistive Sensor 21 Reference layer 210 Reference magnetization 211 First reference layer, soft reference layer 212 Connecting layer 213 Second reference layer, hard reference layer 22 Tunnel Barrier Layer 23 Sense Layer 230 Sense Magnetization 231 First Part 232 Second part, oxide insert 233 Layer A 234 Layer B 24, 25 Cap Layer 26 Interface layer 31 Measurement current 60 External magnetic field χ magnetic susceptibility H PMA Perpendicular magnetic anisotropy field S Sensitivity V out Output Voltage

Claims

1. a reference layer (21) having a reference magnetization (210) oriented out of plane; a sense layer (23) having a sense magnetization (230) with a stable vortex-like morphology in the presence of an external magnetic field (60), the sense magnetization (230) being reversibly movable in an out-of-plane direction relative to the reference magnetization (210) when the external magnetic field (60) is changed in an out-of-plane direction; a tunnel barrier layer (22) between the reference layer (21) and the sense layer (23); Equipped with the sense layer (23) has a thickness of less than 200 nm; The sense layer (23) is The sense magnetization (230) is 300 emu / cm ３ to 1400 emu / cm ３ Between The sense layer (23) is 79.6×10 ３ Perpendicular magnetic anisotropy field (H ＰＭＡ ) A magnetoresistive element comprising a ferromagnetic material configured as follows:

2. The sense layer (23) is made of a soft ferromagnetic material and the perpendicular magnetic anisotropy field (H ＰＭＡ 13. The magnetoresistive element of claim 1 further comprising a reinforcing material configured to enhance the magnetoresistance.

3. The magnetoresistive element of claim 2 , wherein the soft ferromagnetic material comprises a NiFe, CoFe, or CoFeB alloy.

4. The reinforcing material is (Co / Pt) ｎ , (Co / Pd) ｎ , (Co / Au) ｎ , (Co / Fe) ｎ , (CoCr / Pt) ｎ , (NiFe / Cu) ｎ , or (Co / Cu) ｎ 4. The magnetoresistive element of claim 2, further comprising a stack including any one of:

5. A magnetoresistive element according to claim 2 or 3, wherein the reinforcing material comprises an oxide insert (232) in the soft ferromagnetic material.

6. The magnetoresistive element of claim 5 , wherein the oxide insert comprises one continuous layer (232) or a plurality of continuous layers (232).

7. The magnetoresistive element of claim 5 , wherein the oxide insert comprises a plurality of clusters (232).

8. A magnetoresistive element according to claim 5 , wherein the oxide insert comprises MgO.

9. A magnetoresistive element according to claim 4 or 6, wherein the reinforcing material has a thickness between 0.1 nm and 2 nm.

10. The sense layer (23) is (NiFe / Ni) ｎ , (Ni / Co) ｎ , or (NiFe / Co) ｎ 2. The magnetoresistive element of claim 1, further comprising a stacked structure including one of: n = n + ...

11. The magnetoresistive element of claim 1 , wherein the ferromagnetic material comprises a Heusler alloy.

12. The magnetoresistive element of claim 11 , wherein the ferromagnetic material comprises a Mn-containing alloy.

13. The magnetoresistive element of claim 12 , wherein the ferromagnetic material comprises a NiMnGa, CoMnGa, FeMnGa, CoFeSi, CoMnSi, NiMnSb, CoMnSb, or CoMnAl alloy.

14. The ferromagnetic material is Co ２ FeAl, MnAs, MnSb, CoTb, NdCo ５ , or SmCo ５ The magnetoresistive element of claim 11 comprising an alloy.

15. A magnetoresistive sensor comprising a plurality of magnetoresistive elements (2) according to any one of the preceding claims.

16. 16. The magnetoresistive sensor of claim 15 arranged in a Wheatstone circuit and having an out-of-plane sensitivity of greater than 1 mV / V / mT.

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