Magnetoresistance element and sensor including magnetoresistance element having thermally robust performance after exposure to high magnetic fields - Patents.com

Abstract

The magnetoresistive element (2) comprises a reference layer (23) having a fixed reference magnetization (230), a ferromagnetic sense layer (21) having a free sense magnetization (210) with a stable vortex configuration that can be oriented relative to the fixed reference magnetization (230) in the presence of an external magnetic field (60), and a tunnel barrier layer (22) between the reference layer (23) and the sense layer (21) and in contact with a first side (211) of the sense layer (21). The magnetoresistive element (2) further comprises a hard magnetic layer (25) configured on a second side (212) of the sense layer (21) opposite the first side (211), the hard magnetic layer (25) configured to generate an interfacial magnetic coupling between the hard magnetic layer (25) and the sense layer (21) on the second side (212), such as to prevent chirality switching of the sense magnetization (210) after the magnetoresistive element (2) is subjected to heat treatment and an external magnetic field exceeding the eddy rejection magnetic field.

Description

[Technical field]

[0001]

[0001] The present disclosure relates to a magnetoresistive element adapted to sense an external magnetic field and having a broad linear response and a rated performance that remains substantially unchanged after the magnetoresistive element is subjected to a high magnetic field. The present disclosure further relates to a magnetic sensor including a plurality of magnetoresistive elements. The present disclosure further relates to a method for manufacturing the magnetoresistive element. [Background technology]

[0002] A magnetoresistive sensor element based on tunnel magnetoresistance (TMR) typically includes a pinned ferromagnetic reference layer with a fixed (pinned) reference magnetization, a ferromagnetic sense layer with a free sense magnetization (which can be oriented in a magnetic field relative to the fixed reference magnetization), and a tunnel barrier layer between the reference layer and the sense ferromagnetic layer. An external magnetic field can thus be sensed by measuring the resistance of the magnetoresistive sensor element. The resistance depends on the orientation and magnitude of the averaged sense magnetization relative to the reference magnetization. The sense magnetization can include a vortex configuration, whereby the magnetization is spiraled in a circular path along the edge of the sense layer. The vortex configuration provides linear and non-hysteretic behavior in a large range of external magnetic fields. The vortex configuration is advantageous for magnetic sensor applications. A magnetoresistive sensor including a magnetoresistive sensor element with a vortex configuration can provide a small footprint and reduced current consumption. Such magnetoresistive sensors compete favorably with semiconductor sensors based on the Hall effect.

[0003]

[0003] A magnetoresistive sensor element may include an antiferromagnetic layer that is exchange coupled to the reference layer, such as to pin the reference magnetization. The strength and uniformity of the exchange coupling have a strong effect on the electrical response characteristics of the magnetoresistive sensor and its long-term stability.

[0004]

[0004] Magnetoresistive sensor elements are typically fabricated and magnetically tuned (to write to the reference layer). To improve long-term stability, the tuned magnetoresistive sensor elements are subjected to a high-temperature heat treatment (baking) to tune and stabilize the magnetic and electrical properties of the magnetoresistive sensor elements. The magnetoresistive sensor elements may further be subjected to a permeability test using a magnetic field of more than 200 mT. During the heat treatment, the layers of the magnetoresistive sensor element relax towards a more stable magnetic state. However, the relaxation of the antiferromagnetic layer during the heat treatment may lead to a significant growth of full cycle hysteresis that reduces the accuracy of the magnetoresistive sensor element.

[0005]

[0005] The inventors have shown that heat treatment reduces the uniformity of the direction of the pinned reference magnetization of the reference layer. The pinned reference magnetization is distorted, and the distortion is "frozen" when the temperature of the magnetoresistive sensor element is reduced after completion of heat treatment. Typically, the distortion has a certain degree of chirality, which makes the electrical resistance of the magnetoresistive sensor element sensitive to the (usually variable) vortex chirality in the sensing layer. Exposure to a high magnetic field (close to or exceeding the vortex elimination field) affects chirality switching, which induces different conductivity levels. For example, chirality switching without chiral distortion (produced after high magnetic field exposure) will induce two energetically equivalent states with similar conductivity levels, while chirality switching with chiral distortion will generate different conductivity levels due to asymmetric magnetic distortion in the reference layer 21. Thus, distortion can result in reduced accuracy, reproducibility, and repeatability in the operation of the magnetoresistive sensor element.

[0006]

[0006] Furthermore, magnetoresistive sensor elements can suffer from a reduced usable measurement magnetic field range and reduced sensitivity. More generally, electrical offset drift after exposure to high magnetic fields (full cycle hysteresis) is a serious problem observed in vortex-based magnetoresistive sensors, limiting their performance when they are exposed to high magnetic fields.

[0007]

[0007] Previous solutions to reduce distortion induced by thermal processing and high magnetic fields include partially changing the aspect ratio and material of the sense layer to increase the rejection field, modifying the shape of the magnetoresistive sensor element to block chirality switching, and increasing the thermal stability of the antiferromagnetic layer that exchange couples to the reference layer to reduce its degradation during thermal processing.

[0008]

[0008] European Patent Application EP20200315443, filed by the present inventors on November 3, 2020, discloses a magnetoresistive sensor element including a sense antiferromagnetic layer that pins a vortex sensing layer and a reference antiferromagnetic layer that pins a reference layer, the cutoff temperature of the sense antiferromagnetic layer being less than the cutoff temperature of the reference antiferromagnetic layer. Summary of the Invention

[0009]

[0009] The present disclosure relates to a magnetoresistive element including a reference layer having a fixed reference magnetization, a ferromagnetic sense layer having a free sense magnetization with a stable vortex configuration that can be oriented relative to the fixed reference magnetization in the presence of an external magnetic field, and a tunnel barrier layer between the reference layer and the sense layer and in contact with a first side of the sense layer. The magnetoresistive element further includes a hard magnetic layer configured on a second side of the sense layer opposite the first side, the hard magnetic layer configured to generate an interfacial magnetic coupling between the hard magnetic layer and the sense layer on the second side, such as to prevent chirality switching of the sense magnetization, after the magnetoresistive element is subjected to a heat treatment and an external magnetic field exceeding the vortex rejection field.

[0010] In an embodiment, the sense layer has a net exchange bias in any direction in the plane of the sense layer that is less than 40 A / m.

[0011]

[0011] The present disclosure further relates to a method for manufacturing a magnetoresistive element, comprising: forming a reference layer, a tunnel barrier layer, a sense layer, and a hard magnetic layer; measuring the net exchange bias of the magnetoresistive element; heating the magnetoresistive element 2 to a heating temperature between 150° C. and 400° C. until the measured net exchange bias of the magnetoresistive element 2 is less than 40 A / m; It relates to the fact that it can include.

[0012]

[0012] The disclosed magnetoresistive elements do not exhibit increased hysteresis after being subjected to high temperature heat treatment and / or high magnetic fields (close to or exceeding the eddy-exclusion field of the sense layer). The magnetoresistive elements are therefore robust to thermal degradation and subsequent offset drift. In fact, heat treatment can be performed at temperatures higher than those used in conventional magnetoresistive elements.

[0013]

[0013] The magnetoresistance element can be manufactured using conventional manufacturing processes. In fact, the disclosed magnetoresistance element does not require modification of the shape of the magnetoresistance element, the latter being able to have a conventional shape. In contrast to prior art solutions, the disclosed magnetoresistance element can use a wide range of antiferromagnetic and hard magnetic materials to achieve the desired effects mentioned above. The antiferromagnetic layer can be grown in a conventional manner.

[0014]

[0014] Exemplary embodiments of the invention are disclosed in the description and illustrated in the drawings. [Brief description of the drawings]

[0015] [Figure 1] FIG. 2 illustrates a magnetoresistive element including a reference layer and a sense layer, according to an embodiment. [Diagram 2] FIG. 2a shows a top view of a sense layer having a sense magnetization that includes a vortex configuration in the absence of an external magnetic field, and FIG. 2b shows a top view of a sense layer having a sense magnetization that includes a vortex configuration in the presence of an external magnetic field. [Diagram 3] FIG. 2 illustrates a magnetoresistive element where the reference layer has a synthetic antiferromagnetic structure. [Figure 4]FIG. 2 illustrates an example magnetic sensor including multiple magnetoresistive elements, according to an embodiment. [Diagram 5] FIG. 1 shows a graph reporting the normalized magnetization as a function of magnetic field measured for a magnetoresistive element. [Figure 6] FIG. 6 shows an expanded portion of the magnetization curve of FIG. 5 between −50 Oe and 50 Oe. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] 1 shows a magnetoresistive element 2 according to an embodiment. The magnetoresistive element 2 includes a reference layer 23 having a pinned reference magnetization 230, a sense layer 21 having a free sense magnetization 210 that can be oriented relative to the fixed reference magnetization 230 in the presence of an external magnetic field 60, and a tunnel barrier layer 22 between the sense layer 21 and the reference layer 23. A first side 211 of the sense layer 21 contacts the tunnel barrier layer 22.

[0017] Each of the reference layer 23 and the sense layer 21 may include or be formed of a magnetic material, in particular a ferromagnetic type magnetic material. The sense ferromagnetic layer 21 may include a soft ferromagnetic material, i.e. a soft ferromagnetic material having a relatively low coercivity, while the reference ferromagnetic layer 23 may include a hard ferromagnetic material, i.e. a hard ferromagnetic material having a relatively high coercivity. In that way, the sense magnetization 210 of the sense ferromagnetic layer 21 may be easily varied under a low strength magnetic field, while the reference magnetization 230 of the reference layer 23 is held fixed and used as a reference layer. Suitable ferromagnetic materials include transition metals, rare earth elements, and their alloys with or without main group elements. For example, suitable ferromagnetic materials include iron ("Fe"), cobalt ("Co"), nickel ("Ni"), and alloys thereof, such as permalloy (or Ni80Fe20), alloys based on Ni, Fe, and boron ("B"), Co90Fe10, and alloys based on Co, Fe, and B. In some instances, alloys based on Ni and Fe (and optionally B) may have a lower coercivity than alloys based on Co and Fe (and optionally B).

[0018]

[0017] The sense layer 21 is in contact with the tunnel barrier layer 22. The sense layer 21 includes a soft magnetic material and a free sense magnetization 210 that can be oriented relative to a fixed reference magnetization 230 in the presence of an external magnetic field 60. The reference magnetization 230 remains substantially undisturbed. The sense magnetization 210 has a stable vortex configuration in the absence of an external magnetic field. The external magnetic field 60 can therefore be sensed by measuring the resistance of the magnetoresistance element 2. The resistance depends on the orientation of the sense magnetization 210 relative to the reference magnetization 230.

[0019] In one embodiment, the reference layer 23 and the sense layer 21 include or are formed of ferromagnetic materials such as cobalt ("Co"), iron ("Fe"), or nickel ("Ni") based alloys, and preferably CoFe, NiFe, or CoFeB based alloys. The reference layer 23 can have a thickness between 2 nm and 7 nm. The reference layer 23 and the sense layer 21 can include ferromagnetic materials such as Co, Fe, or Ni based alloys, and preferably CoFe, NiFe, or CoFeB based alloys, and non-magnetic materials such as Ta, Ti, W, Ru, Ir, etc. The ferromagnetic material(s) and non-magnetic material(s) can be co-deposited or / and multi-layered.

[0020]

[0019] The sense magnetization 210 includes a stable vortex configuration that rotates around a center 2101 in a circular path along the edge of the sense layer 21 and can be reversibly moved by an external magnetic field 60 (see FIG. 2a). FIG. 2a shows the sense magnetization 210 when the center 2101 of the vortex configuration is substantially in the center of the sense layer cross section and there is no external magnetic field 60. In this configuration, the sense layer 21 has a net magnetic moment that is substantially zero (M=0). FIG. 2b shows the sense magnetization 210 in the presence of an external magnetic field 60. The external magnetic field 60 causes the center 2101 to move in a direction approximately perpendicular to one of the external magnetic fields 60 (indicated by the dotted arrow). The displacement of the center 2101 results in a net magnetic moment (M≠0) in the sense layer 21.

[0021] In a desired configuration, the sense layer 21 has a thickness greater than 15 nm.

[0022]

[0021] In a variant, the magnetoresistive element 2 can include a reference antiferromagnetic layer 24 disposed adjacent to the reference layer 23, which pins the reference magnetization 230 along a particular direction through exchange bias when the temperature in or around the reference antiferromagnetic layer 24 is at a low threshold temperature TL of the reference antiferromagnetic layer 24, i.e., below a cutoff temperature such as the Neel temperature or another threshold temperature. The reference antiferromagnetic layer 24 unpins or frees the reference magnetization 230 when the temperature is at a high threshold temperature TH, i.e., above the cutoff temperature, thereby allowing the reference magnetization 230 to be switched to another direction. In this configuration, writing to the reference layer 23 can include a step of heating the magnetoresistive element 2 to a high threshold temperature TH, such as to unpin the reference magnetization 230, while programming the magnetic field. Once the reference magnetization 230 has been switched to the written direction, the magnetoresistive element 2 may be cooled to a low threshold temperature TL, such as to pin the reference magnetization 230 to the written direction.

[0023]

[0022] Other implementations of the sense layer 21 and the reference layer 23 are contemplated. For example, either or both of the sense layer 21 and the reference layer 23 can include multiple sublayers in a manner similar to the multiple sublayers of a so-called synthetic antiferromagnetic layer. In the configuration shown in Figure 3, the reference layer 23 has a synthetic antiferromagnetic structure including at least a first ferromagnetic reference layer 231 and a second ferromagnetic reference layer 232 separated and antiferromagnetically coupled through an intervening nonmagnetic layer 233. The nonmagnetic layer is typically a Ru layer, but may further include any of Ru, Ir, or Cu, or a combination of these elements. In the antiferromagnetic structure, the reference magnetization 230 of the first ferromagnetic layer 231 is antiparallel coupled to the reference magnetization 230 by the nonmagnetic layer 233. When the magnetoresistive element 2 includes a reference antiferromagnetic layer 24 , the reference magnetic field 230 of the second ferromagnetic layer 232 adjacent to the antiferromagnetic layer 24 is pinned by the antiferromagnetic layer 24 .

[0024]

[0023] The tunnel barrier layer 22 includes or is formed of 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 can be in the nm range, such as about 1 nm to about 10 nm. Large TMR, for example up to 200%, can be obtained for a magnetic tunnel junction 2 including a crystalline MgO-based tunnel barrier layer 22.

[0025] When the magnetoresistive element 2 is subjected to high temperature heat treatment (baking) and high magnetic fields, i.e., fields exceeding the vortex rejection field, substantially similar chiral distortions are produced in the sense layer 21 and the reference layer 23. The chiral distortions favor a particular vortex chirality in vortex sensing.

[0026] In an embodiment, the magnetoresistive element 2 further includes a hard magnetic layer 25 configured on a second side 212 of the sense layer 21 opposite the first side 211. The hard magnetic layer 25 is configured to generate an interfacial magnetic coupling between the hard magnetic layer 25 and the sense layer 21 at the second side 212. The interfacial magnetic coupling can “freeze” (i.e., pin) the sense magnetic 210 in at least a portion of the sense layer 21 such that chirality switching of the sense magnetic 210 due to chiral distortion generated in the sense layer 21 is prevented.

[0027]

[0026] According to the simulation and experimental data made by the present inventors, the chiral distortion in the sense layer 21 is "frozen" (i.e., pinned) by the hard magnetic layer 25 so as to substantially compensate the chiral distortion in the reference layer 23. In other words, the pinned chiral distortion in the sense layer 21 can offset the negative effect of the pinned chiral distortion in the reference layer 23, and thus significantly reduce the enhancement of hysteresis in the magnetoresistance element 2 after heat treatment. The magnetoresistance element 2 is therefore robust against thermal degradation of offset shift after exposure to high magnetic fields.

[0028] In embodiments, the hard magnetic layer 25 includes a material having a high magnetic coercivity (eg, greater than 500 A / m, 1000 A / m, 1500 A / m, or 2000 A / m).

[0029]

[0028] In one aspect, high magnetic coercivity can be obtained by a material including exchange debonding grains such as any one of CoCrPt, FePt-TiO2, FePt-SiO2, FePt-C, CoPt, NdFeB, or SmCo, alone or in combination.

[0030]

[0029] High magnetic coercivity materials may further include perpendicular ferromagnetic alloys including rare earths such as Tb, Gd, Sm, and transition metals (such as Co, Fe, or CoFe).

[0031]

[0030] The high magnetic coercivity material may further include an L10 type perpendicularly ordered alloy, which may be a CoPt or FePt type alloy.

[0032]

[0031] The high magnetic coercivity material may further comprise multilayers of 3d-4d metals exhibiting perpendicular magnetic anisotropy, such as Co, Fe, CoFe, Ni, Pt, Pd, Au, or Ag.

[0033]

[0032] The high magnetic coercivity material may further include rare earth based permanent magnets, for example 1-5 or 2-17 type alloys (such as SmCo) or RE2Fe 14 B-type alloys (where RE can be Nd, Dy, Pr, etc.).

[0034]

[0033] High magnetic coercivity materials may include slightly debonded grains, which may be accomplished, for example, by incorporating small amounts of Cr, C, Cu, V, or oxides into the alloy.

[0035] In another embodiment, the hard magnetic layer 25 can include an antiferromagnetic material, which can include any one of IrMn, FeMn, PtMn, PdMn, CrPdMn, NiMn, CuMnAs, Mn3Sn, Mn2Au, Cr2O, etc., alone or in combination.

[0036] The cutoff temperature, such as the Neel temperature or another threshold temperature, of the antiferromagnetic material forming the hard magnetic layer 25 can be varied by varying the thickness of the antiferromagnetic material comprising the hard magnetic layer 25.

[0037] In an embodiment, the thickness of the hard magnetic layer 25 is between 2 nm and 30 nm.

[0038] The magnetoresistive element 2 further includes an intermediate layer 26 between the hard magnetic layer 25 and the sense layer 21. The intermediate layer 26 is configured to adjust the strength of the interface magnetic coupling between the hard magnetic layer 25 and the sense layer 21. The thickness of the intermediate layer 26 is set to adjust the strength of the interface magnetic coupling to within -1 mJ / m 2 and +1mJ / m 2 The input signal may be configured to adjust to a value between

[0039] In one embodiment, the intermediate layer 26 includes a transition metal. The transition metal can include any one of Ru, W, Ir, or Ta.

[0040] In a preferred configuration, the intermediate layer 26 is not in contact with the hard magnetic layer 25.

[0041] In one embodiment, the magnetoresistive element 2 may further include a ferromagnetic coupling layer 27 between the intermediate layer 26 and the hard magnetic layer 25. In such a configuration, the hard magnetic layer 25 is configured to generate an interfacial magnetic coupling between the hard magnetic layer 25 and the coupling layer 27 at the interface between the hard magnetic layer 25 and the coupling layer 27.

[0042] The strength of the interfacial magnetic coupling between the hard magnetic layer 25 and the sense layer 21 can be further adjusted by adjusting the thickness of the ferromagnetic coupling layer 27.

[0043]

[0042] In an embodiment, the magnetic sensor includes a plurality of magnetoresistance elements 2. The magnetoresistance elements 2 may be connected in parallel and / or in series by non-magnetic electrodes or conductors. The magnetoresistance elements 2 may be configured such that the magnetic sensor forms a full-bridge configuration or a half-bridge configuration.

[0044] 4 illustrates an exemplary magnetic sensor 200 configured in a bridge circuit. In one embodiment, the bridge circuit may include at least a first branch 201 including two series-connected magnetoresistance elements 2 and a second branch 202 including two series-connected magnetoresistance elements 2. Each magnetoresistance element 2 in the first branch 201 may have its reference magnetization 230 adjusted in an opposite direction to the adjusted direction of the reference magnetization 230 of the magnetoresistance element 2 in the second branch 202.

[0045] In one embodiment, the lateral size of the magnetoresistive element 2 is between 100 nm and 1000 nm.

[0046] The magnetoresistive element 2 may have a circular, elliptical or non-centrosymmetric shape.

[0047] In a further embodiment, the magnetoresistive element 2 may be configured such that the sense layer 21 has a net exchange bias of less than 40 A / m (0.5 Oe) in any direction along the plane P of the sense layer 21. Referring again to Figures 1, 2a and 2b, the different directions perpendicular to and along the plane P of the sense layer 21 are represented by axes x, y and z.

[0048] A net exchange bias of less than 40 A / m can be obtained by subjecting the magnetoresistive element 2 to a heat treatment.

[0049] In an embodiment, the method for manufacturing the magnetoresistive element 2 thus comprises: forming a reference layer 23, a tunnel barrier layer 22, a sense layer 21, and a hard magnetic layer 25; measuring the net exchange bias of the magnetoresistive element 2; heating the magnetoresistive element 2 to a heating temperature between 150° C. and 400° C. until the measured net exchange bias of the magnetoresistive element 2 is less than 40 A / m; may include.

[0050] Depending on the heating temperature, the heating of the magnetoresistance element 2 can be performed for a heating time between 1 second and 24 hours. In some embodiments, the heating temperature can be between 300°C and 400°C (such as 350°C or 360°C) and the heating time is between 1 second and 1 hour. For example, the heating of the magnetoresistance element 2 can be performed using rapid heat treatment (or rapid thermal annealing) or flash annealing.

[0051] The net exchange bias can be measured using magnetic measurement techniques.

[0052] The method may further include forming an intermediate layer 26 between the hard magnetic layer 25 and the sense layer 21.

[0053] The method may further include forming a ferromagnetic coupling layer 27 between the intermediate layer 26 and the hard magnetic layer 25.

[0054]

[0053] Figures 5 and 6 show graphs reporting the normalized magnetization as a function of the magnetic field (in Oe) measured for the magnetoresistance element 2. Figure 5 shows the complete measured magnetization curve between -800 Oe and 800 Oe, and Figure 6 shows an enlarged portion of the magnetization curve of Figure 5 between -50 Oe and 50 Oe.

[0055]

[0054] The net exchange bias can be determined by measuring the shift of the magnetization curve along the magnetic field coordinate relative to a magnetic field of zero value. For example, in Fig. 5 and Fig. 6, the magnetization curve A is measured for the magnetoresistance element 2 before the heat treatment and the magnetization curve B is measured for the magnetoresistance element 2 after the heat treatment. It can be seen that the magnetization curve A is shifted along the magnetic field coordinate by about 25 Oe relative to zero magnetic field (the magnetization curve A extends between about -650 Oe and 600 Oe). In this case, the net exchange bias is therefore approximately 2000 A / m (25 Oe). The magnetization curve B extends between about -700 Oe and 700 Oe and is centred on zero magnetic field. The net exchange bias is therefore substantially 0 A / m. It can further be seen from Fig. 6 that at low magnetic fields (at least between -50 Oe and 50 Oe), the heat treatment leads to a hysteresis that is substantially zero. For example, the hysteresis can be less than 8 A / m (0.1 Oe).

[0056]

[0055] The magnetoresistance element 2 subjected to the heat treatment can therefore have a net exchange bias in any direction in the plane P of the sense layer 21 below 40 A / m (for the planes x, y, see Figures 2a and b). The magnetoresistance element 2 further has a hysteresis that is substantially zero. The magnetoresistance element 2 therefore has an improved sensitivity and signal-to-noise ratio. [Explanation of symbols]

[0057] 2. Magnetoresistance element 21 Sensation Layer 200 Magnetic Sensor 201 First Branch 202 Second Branch 210 Sense Magnetization 211 first side of the sense layer 212 second side of the sense layer 2101 Center 22 Tunnel Barrier Layer 23 Reference layer 230 Reference magnetization 231 First ferromagnetic reference layer 232 Second Ferromagnetic Reference Layer 233 Nonmagnetic layer 24 Reference antiferromagnetic layer 25 Hard magnetic layer 26 Middle Class 27 Connecting layer 60 External Magnetic Field

Claims

1. A magnetoresistive element (2), a reference layer (23) having a fixed reference magnetization (230); a ferromagnetic sense layer (21) having a free sense magnetization (210) with a stable vortex configuration orientable relative to said fixed reference magnetization (230) in the presence of an external magnetic field (60); a tunnel barrier layer (22) between the reference layer (23) and the sense layer (21) and in contact with a first side (211) of the sense layer (21); It is equipped with The magnetoresistance element (2) further comprises: a hard magnetic layer (25) configured on a second side (212) of the sense layer (21) opposite the first side (211); A magnetoresistance element (2), wherein the hard magnetic layer (25) is configured to generate an interfacial magnetic coupling between the hard magnetic layer (25) and the sense layer (21) of the second side (212), such as to prevent chirality switching of the sense magnetization (210), after the magnetoresistance element (2) is subjected to a heat treatment and the action of an external magnetic field exceeding an eddy rejection magnetic field.

2. The magnetoresistive element of claim 1, wherein the hard magnetic layer (25) comprises a material having a magnetic coercivity greater than 1000 A / m.

3. The material is CoCrPt, FePt-TiO ２ , FePt-SiO ２ 3. The magnetoresistive element of claim 2, comprising any one of the following, alone or in combination: FePt--C, CoPt, NdFeB, or SmCo.

4. 3. The magnetoresistive element of claim 2, wherein the high magnetic coercivity material comprises any one of a perpendicular ferromagnetic alloy containing rare earth and transition metals, a perpendicular ordered alloy, a multilayer of 3d-4d metals with perpendicular magnetic anisotropy, and a permanent magnet based on one or more rare earth metals.

5. The magnetoresistive element of claim 3 or 4, wherein the high magnetic coercivity material further comprises Cr, C, Cu, V, or an oxide.

6. The magnetoresistive element of claim 1, wherein the hard magnetic layer (25) comprises an antiferromagnetic material.

7. The antiferromagnetic material is IrMn, FeMn, PtMn, PdMn, CrPdMn, NiMn, CuMnAs, Mn ３ Sn, Mn ２ Au or Cr ２ 7. The magnetoresistive element of claim 6, comprising any one of, alone or in combination, O.

8. A magnetoresistive element according to any one of the preceding claims, wherein the thickness of the hard magnetic layer (25) is between 2 and 30 nm.

9. 9. The magnetoresistive element of claim 1, further comprising an intermediate layer (26) between the sense layer (21) and the hard magnetic layer (25), and the strength of the interface magnetic coupling is adjustable by adjusting a thickness of the intermediate layer (26).

10. A magnetoresistive element according to claim 9, wherein the intermediate layer (26) comprises a transition metal, in particular Ru, W, Ir or Ta.

11. The thickness of the intermediate layer (26) is such that the strength of the interface magnetic coupling is −1 mJ / m ２ and +1 mJ / m ２ 11. The magnetoresistive element of claim 9 or 10, configured to have a value between

12. further comprising a ferromagnetic coupling layer (27) between the intermediate layer (26) and the hard magnetic layer (25); A magnetoresistive element according to any one of claims 9 to 11, wherein the strength of the interfacial magnetic coupling is further adjustable by adjusting the thickness of the coupling layer (27).

13. The magnetoresistive element of any one of claims 1 to 12, wherein the soft magnetic material of the sense layer (21) comprises a combination of Ni, Fe, Co, and a transition metal.

14. The magnetoresistive element of claim 13, wherein the sense layer (21) has a thickness greater than 15 nm.

15. A magnetoresistive element according to any one of claims 1 to 14, wherein the sense layer (21) has a net exchange bias in any direction in the plane (P) of the sense layer (21) that is lower than 40 A / m.

16. A magnetic sensor (200) including a plurality of magnetoresistance elements (2).

17. A method for manufacturing a magnetoresistive element (2), comprising the steps of: forming a reference layer (23), a tunnel barrier layer (22), a sense layer (21), and a hard magnetic layer (25); measuring the net exchange bias of the magnetoresistive element (2); heating the magnetoresistive element (2) to a heating temperature between 150° C. and 400° C. until the measured net exchange bias of the magnetoresistive element (2) is less than 40 A / m; The method may include:

18. 18. The method according to claim 17, wherein the heating of the magnetoresistive element (2) is performed for a heating time between 1 second and 24 hours.

19. 19. The method of claim 17 or 18, wherein the measurement of the net exchange bias is performed using a magnetic measurement technique.

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