A magnetoresistive sensor element that detects two-dimensional magnetic fields with small error in high magnetic fields

Abstract

To reduce errors in sensing two-dimensional high magnetic fields. The magnetoresistive element (2) for a two-dimensional magnetic field sensor of the present invention includes a ferromagnetic reference layer (21) having a fixed reference magnetization (210), a ferromagnetic sense layer (23) having a sense magnetization (230) that is freely orientable with respect to the reference magnetization (210) in the presence of an external magnetic field, and a tunnel barrier layer (22) between the reference magnetization layer (21) and the sense ferromagnetic layer (23). The reference layer (21) includes a reference coupling layer (213) between a reference pinned layer (211) and a reference coupled layer (212). The reference coupled layer (212) includes a first coupled sublayer (214) in contact with the reference coupling layer (213), a second coupled sublayer (215), a third coupled sublayer (217), and an insertion layer (216) between the second and third coupled sublayers (215, 217). The intercalating layer (216) is made of a transition metal and has a thickness of about 0.1 to about 0.5 nm, and the reference bonded layer (212) has a thickness of between about 1 nm and about 5 nm.

Description

[Technical field]

[0001] The present invention relates to a magnetoresistive sensor element for sensing a two-dimensional (2D) magnetic field with small error in high magnetic fields, and also to a magnetic field sensor comprising such a magnetoresistive element. [Background technology]

[0002] Magnetic sensor elements based on the tunneling magnetoresistance (TMR) effect can be used for 2D magnetic field detection. Such magnetic sensor elements typically comprise a ferromagnetic reference layer with a fixed reference magnetization, a tunnel barrier layer with a sense magnetization that is freely oriented with respect to the reference magnetization in the presence of a magnetic field, and a ferromagnetic sense layer. The reference layer may comprise a synthetic antiferromagnetic (SAF) structure comprising a fixed first ferromagnetic reference layer, a coupled spacer layer, and a second ferromagnetic reference layer in contact with an antiferromagnetic layer. To have good accuracy, the magnetic sensor element should have low angular error in high magnetic fields.

[0003] Low angular error at high magnetic fields can be achieved by increasing the stiffness of the SAF structure. Increasing the stiffness of the SAF structure is usually achieved by decreasing the thickness of the first and second ferromagnetic reference layers. For example, the thickness of the first and second ferromagnetic layers is decreased to 1.0 nm. This results in an increase in the saturation field Hsat of the magnetic sensor element. The magnetization of the SAF structure becomes more stable (rigid) at high applied magnetic fields. However, decreasing the thickness of the first and second ferromagnetic reference layers impairs the magnetotransport properties of the magnetic sensor element. Such a small thickness also results in a loss of pinning by the antiferromagnetic (AF) layer, resulting in a very low TMR response of the magnetic sensor element.

[0004] Patent Document 1 (US2011134563) relates to a magnetoresistive head comprising a magnetic pinning layer, a free magnetic layer located above the magnetic pinning layer, and a tunnel barrier layer, where at least one of the magnetic pinning layer and the free magnetic layer has a layered structure, comprising a CoFe magnetic layer or a CoFeB magnetic layer, an amorphous magnetic layer comprising CoFeB and a selected element, a CoFeB magnetic layer, and a crystalline layer containing any element selected from Ta, Hf, Zr, and Nb, where the crystalline layer is located closer to the tunnel barrier layer than the amorphous magnetic layer.

[0005] Patent document 2 (US2012257298) describes a TMR head having an antiferromagnetic (AFM) layer, a first ferromagnetic layer above the AFM layer, a second ferromagnetic layer above the first ferromagnetic layer, an AF coupling layer between the first and second ferromagnetic layers, a pinned layer above the second ferromagnetic layer, an insertion layer within or adjacent to the pinned layer, a barrier layer above the pinned layer, and a free layer above the barrier layer.

[0006] US2020066790 describes a stack of materials comprising a first magnetoresistance element having a first response direction to an external magnetic field, opposite to the first response direction, and a second magnetoresistance element having a second response direction to an external magnetic field. The first magnetoresistance element can be disposed below or above the second magnetoresistance element. An insulating layer separates the first and second magnetoresistance elements.

[0007] US8582253 discloses a magnetic sensor having a highly spin-polarized reference layer stack on an AFM layer, the reference layer stack comprising a first boron-free ferromagnetic layer on the AFM coupling layer, a magnetic coupling layer on and in contact with the first boron-free ferromagnetic layer, a second ferromagnetic layer containing boron deposited on and in contact with the magnetic coupling layer, and a third ferromagnetic layer containing boron on and in contact with the second ferromagnetic layer.

[0008] Patent Document 5 (US2015162525) discloses a magnetic storage device including a magnetic tunnel junction memory element that may include a reference magnetic layer, a tunnel barrier layer, and a free magnetic layer. The reference magnetic layer may include a first fixed layer, an exchange coupling layer, and a second pinned layer. The exchange coupling layer may be between the first and second pinned layers, and the second pinned layer may include a ferromagnetic layer and a nonmagnetic layer. The second pinned layer may be between the first pinned layer and the tunnel barrier layer, and the tunnel barrier layer may be between the reference magnetic layer and the free magnetic layer. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] US Patent Application Publication No. 2011 / 134563 [Patent Document 2] US Patent Application Publication No. 2012 / 257298 [Patent Document 3] US Patent Application Publication No. 2020 / 066790 [Patent Document 4] U.S. Patent No. 8,582,253 [Patent Document 5] US Patent Application Publication No. 2015 / 162525 Summary of the Invention

[0010] The present disclosure relates to a magnetoresistive element for a two-dimensional magnetic field sensor, the magnetoresistive element comprising a ferromagnetic reference layer having a fixed reference magnetization, The ferromagnetic reference layer comprises a ferromagnetic sense layer having a sense magnetization freely orientable with respect to the reference magnetization in the presence of an external magnetic field, and a tunnel barrier layer between the reference ferromagnetic layer and the sense ferromagnetic layer. The reference layer comprises a reference coupling layer between the reference pinned layer and the reference coupled layer; the reference bonded layer comprises a first bonded sublayer adjacent to the reference bonded layer, a second bonded sublayer, a third bonded sublayer, and an insertion layer between the second bonded sublayer and the third bonded sublayer; the transition metal-containing intercalation layer has a thickness of between about 0.1 and about 0.5 nm; The thickness of the reference bonded layer is between about 1 nm and about 5 nm.

[0011] In one embodiment, the reference pinning layer comprises a CoFe alloy and has a thickness of 2 nm, the tunnel barrier layer comprises Mg, the insertion layer comprises Ta, the first coupled sublayer comprises a CoFe alloy and has a thickness of 0.5 nm, the second coupled sublayer comprises a CoFeB alloy and has a thickness of 0.75 nm, and the third coupled sublayer comprises a CoFeB alloy and has a thickness between 0.45 nm and 0.95 nm. The magnetoresistance element is heat treated at 310° C. for 90 minutes under a magnetic field of about 1 T.

[0012] The present disclosure further relates to a magnetic field sensor for sensing a two-dimensional magnetic field, comprising the above-mentioned magnetoresistance element.

[0013] The magnetoresistance element disclosed herein has a high saturation magnetic field H sat and tunnel magnetoresistance (TMR) response. The magnetoresistance element also has a high stiffness of the SAF reference layer, improving thermal stability. The magnetoresistance element reduces angle errors and improves accuracy even in high magnetic fields. High saturation magnetic field H sat , exchange stiffness (SAF coupling) and the TMR response of the magnetoresistive element are obtained without reducing the magnetic layer thickness of the SAF structure.

[0014] The invention will be better understood with the help of the description of embodiments given as examples and illustrated by the figures. [Brief description of the drawings]

[0015] [Figure 1] FIG. 1 shows a schematic diagram of a magnetoresistive element comprising a ferromagnetic reference layer, a ferromagnetic sense layer and a tunnel barrier layer according to one embodiment. [Diagram 2] FIG. 2 shows a schematic diagram of a sense layer according to a particular configuration. [Diagram 3]FIG. 3 illustrates a reference layer comprising an SAF structure comprising a reference coupling layer between a reference pinned layer and a reference coupled layer, according to one embodiment. [Figure 4] FIG. 4 is a graph reporting the relationship between magnetic saturation field and the thickness of the reference coupled layer. [Diagram 5] FIG. 5 is a graph reporting the relationship between the resistance area product of the magnetoresistive element and the thickness of the reference coupled layer. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] FIG. 1 shows a schematic diagram of a magnetoresistance element 2 according to an embodiment. The magnetoresistance element 2 comprises a ferromagnetic reference layer 21, a ferromagnetic sense layer 23, and a tunnel barrier layer 22 between the reference and sense ferromagnetic layers 21, 23. The reference layer 21 has a fixed reference magnetization 210, and the sense layer 23 has a sense magnetization 230 that can be freely oriented with respect to the reference magnetization 210 in the presence of an external magnetic field 60. In other words, when the magnetoresistance element 2 is in the presence of an external magnetic field 60, the reference magnetization 210 is substantially stationary while the sense magnetization 230 is deflected in the direction of the external magnetic field 60. The magnetoresistance element 2 may further comprise a cover layer 25 on the side of the sense layer 23 and a seed layer 27 on the side of the reference layer 21.

[0017] The capping layer 25 may comprise a layer of TaN, Ru or Ta. The capping layer 25 may comprise multiple layers comprising a layer of any of tantalum nitride (TaN), ruthenium (Ru) or tantalum (Ta), or a combination of these layers. In a particular configuration, the capping layer 25 comprises multiple layers comprising an 80 nm layer of TaN, a 5 nm layer of Ru, a 2 nm layer of TaN, a 5 nm layer of Ru, a 2 nm layer of Ta and a 1 nm layer of Ru. The seed layer 27 may comprise any of Ta, tungsten (W), molybdenum (Mo), titanium (Ti), hafnium (Hf) or magnesium (Mg).

[0018] The tunnel barrier layer 22 may comprise or be 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 may be in the nanometer (nm) range, such as from about 1 nm to about 3 nm. The optimal thickness of the tunnel barrier layer 22 is obtained by inserting multiple (bi- or multi-layer) layers of MgO (or another suitable oxide or insulating material). The tunnel barrier layer 22 may be configured to provide a high TMR, for example, 80% or more.

[0019] The reference layer 21 and the sense layer 23 may comprise or be formed of a magnetic material, particularly a ferromagnetic type of magnetic material. A ferromagnetic material may be characterized by a magnetization with a particular coercivity, which indicates the magnitude of the external magnetic field 60 required to reverse the magnetization 230 after it has been driven to saturation in one direction. Suitable ferromagnetic materials include transition metals, rare earth elements, and their alloys (with or without main group elements). For example, suitable ferromagnetic materials are iron (Fe), cobalt (Co), nickel (Ni), and their alloys, such as NiFe or CoFe alloys, Ni, Fe, and boron (B) based alloys, Co, Fe, and B based alloys, etc. In some examples, Ni and Fe (and optionally B) based alloys may have a smaller coercivity than Co and Fe (and optionally B) based alloys.

[0020] In particular, the reference magnetization 210 and the sense magnetization 230 may be oriented in the plane of the reference layer 21 and the sense layer 23 (in-plane as illustrated in FIG. 1 ), or in a plane substantially perpendicular to the plane of the reference layer 21 and the sense layer 23 (out-of-plane, not shown).

[0021] FIG. 2 shows a schematic diagram of the sense layer 23 according to a particular configuration. The sense layer 23 comprises a first ferromagnetic sense sublayer 231 in contact with the tunnel barrier layer 22, a second ferromagnetic sense sublayer 232, and a non-magnetic sense sublayer 233 between the first and second ferromagnetic sense sublayers 231, 232. The first ferromagnetic sense sublayer 231 may comprise a CoFeB alloy, for example a (CoxFe1-x)80B20 alloy, where x=0.1 to 0.9. The non-magnetic sense sublayer 233 may comprise a layer comprising Ta, W, Mo, Ti, Hf, Mg or Al, or any combination of these elements. The second ferromagnetic sense sublayer 232 may comprise a soft magnetic material with a low in-plane anisotropy value. For example, the second ferromagnetic sense sublayer 232 may comprise a NiFe alloy or a NiFe alloy with B or Cr. In one particular, but non-limiting, aspect, the structure of the sense layer 21 is as follows: CoFeB 1.5 / Ta 0.3 / NiFe4, where the first ferromagnetic sense sublayer 231 contains a 1.5 nm thick CoFeB alloy, the non-magnetic sense sublayer 233 comprises a 0.3 nm thick Ta layer, and the second ferromagnetic sense sublayer 232 comprises a 4 nm thick NiFe alloy. Such a sense layer 23 can have a very low anisotropy field Hk.

[0022] The magnetoresistance element 2 may include an antiferromagnetic layer 24 that exchange-couples the reference layer 21, which fixes (pins) the reference magnetization 210 at a low temperature threshold and releases it at a high temperature threshold. Suitable antiferromagnetic materials include manganese (Mn)-based alloys. The alloys may include, for example, iridium (Ir) and Mn (e.g., IrMn)-based alloys, Fe and Mn-based alloys (e.g., FeMn), platinum (Pt) and Mn (e.g., PtMn or CrPdM)-based alloys, Ni and Mn-based alloys (e.g., NiMn), or oxides such as NiO. Suitable materials for the antiferromagnetic layer 24 may further include an oxide layer such as NiO. In a possible configuration, the antiferromagnetic layer 24 has a thickness of about 4 nm to about 30 nm. Alternatively, the antiferromagnetic layer 24 may include multiple layers, each layer having a thickness between 1 and 10 nm or between 1 and 2 nm. In another arrangement, the antiferromagnetic layer 24 may comprise, for example, a tri-layer configuration with a central antiferromagnetic layer sandwiched between two antiferromagnetic layers with a lower cutoff temperature Tb than the central antiferromagnetic layer. Such a tri-layer arrangement facilitates switching of the reference magnetization 210 when programming the reference layer 21. The antiferromagnetic layer 24 may be separated from the seed layer 27 by an underlayer 26, where the underlayer 26 may comprise Ru, Cu, or a nitride thereof. The underlayer 26 may comprise a thickness between about 1 nm and about 5 nm.

[0023] 3, the reference layer 21 comprises a synthetic antiferromagnetic (SAF) structure comprising a reference coupling layer 213 between the reference pinned layer 211 and the reference coupled layer 212. The reference pinned layer 211 is pinned by an antiferromagnetic layer 24. The reference coupled layer 212 may be coupled to the reference pinned layer 211 by a RKKY coupling mechanism through the reference coupling layer 213. The reference coupling layer 213 may comprise a non-magnetic layer of Ru, Ir or copper (Cu) or a combination thereof.

[0024] In one aspect, the reference bonded layer 212 comprises a first bonded sublayer 214 adjacent to the reference bonded layer 213, a second bonded sublayer 215, and a third bonded sublayer 217. The reference bonded layer 212 may further comprise an insertion layer 216 between the second bonded sublayer 215 and the third bonded sublayer 217.

[0025] The insertion layer 216 comprises a transition metal. The insertion layer 216 comprises Ta, Ti, W, Mo, Hf, Mg, or aluminum (Al), or any combination of these elements. Alternatively, the insertion layer 216 may comprise Ni, chromium (Cr), vanadium (V), or silicon (Si), or any combination of these elements. The insertion layer 216 may be amorphous or quasi-amorphous or nanocrystalline.

[0026] The insertion layer 216 may have a thickness between about 0.1 and about 0.5 nm. Such a thickness of the insertion layer 216 allows for strong magnetic coupling and thus keeps the magnetizations of the second coupled sublayer 215 and the third coupled sublayer 217 parallel to each other aligned. The insertion layer 216 can further increase the tunneling magnetoresistance (TMR) of the magnetoresistive element 2. For example, the TMR can be increased from about 90% without the insertion layer 216 to about 120%. The increased TMR provides a better signal-to-noise ratio of the magnetoresistive element 2 response and a lower dispersion of the magnetoresistive element 2 response.

[0027] The thin insertion layer 216 allows the smoothness of the reference coupled layer 212 at the interface of the reference coupling layer 213 to be maintained or improved. The thin insertion layer 216 increases the RKKY (Ruderman-Kittel-Kasuya-Yoshida, the initials of four physicists) coupling between the reference pinned layer 211 and the reference coupled layer 212 (through the reference coupling layer 213), thereby increasing the stiffness of the reference pinned layer 211 and the reference coupled layer 212. As a result of the high RKKY coupling, the reference magnetization 210 is less likely to be tilted by the external magnetic field 60. Thus, the high RKKY coupling between the reference pinned layer 211 and the reference coupled layer 212 allows a reduction in the angle error with the magnitude of the external magnetic field 60, thus increasing the margin of high magnetic field operation performance of the magnetoresistive element 2. The high RKKY coupling further improves the thermal stability of the magnetoresistive element 2. In one aspect, the RKKY coupling constant energy (J RKKY variable) is approximately 1 erg / cm 2 It is.

[0028] The thin insertion layer 216 further reduces the magnetic saturation field H sat and SAF Combined Exchange Hex The tunnel barrier layer 22 acts as a textured transition layer between the magnetic properties (such as TMR) of the tunnel barrier layer 22 and the electrical properties (such as TMR) of the tunnel barrier layer 22 .

[0029] The magnetoresistive element 2 comprising a transition metal with a thin insertion layer 216 having a thickness of 0.1 to about 0.5 nm has a magnetic saturation magnetic field H sat Compared with the magnetic saturation field H sat by about 5%. This insertion can further increase the TMR of the magnetoresistive element 2 by about 30%. The large TMR reduces the magnetic noise level in the magnetoresistive element 2 response and allows for a reduction in the variance in the magnetoresistive element 2 response between different magnetoresistive elements 2.

[0030] The SAF structure of the reference layer 21 can be compensated for by adjusting the thicknesses of the reference pinned layer 211 and the reference coupled layer 212 such that the macroscopic magnetization is null without a given magnetic field.

[0031] In one aspect, the first bonded sublayer 214 comprises Co or a CoFe alloy. The second bonded sublayer 215 and the third bonded sublayer 217 may comprise Co, Fe, Ni, Cr, V, Si, or B, or any combination of these elements.

[0032] The reference pinning layer 211 may comprise a CoFe alloy or multiple layers of Co or CoFe / CoFeB / CoFe or Co / CoFeB / Co or any other layers containing Co, CoFe and CoFeB.

[0033] The second bonded sublayer 215 may have a thickness of about 1 nm or less, the third bonded sublayer 217 may have a thickness of about 1 nm or less or about 2 nm or less, and the first bonded sublayer 214 may have a thickness of about 1 nm or less.

[0034] In one aspect, the second bonded sublayer 215 has a thickness between 1 and 2 times the thickness of the third bonded sublayer 217 .

[0035] In one embodiment, the total thickness of the reference bonded layer 212 is between about 1 nm and about 5 nm. The total thickness of the reference bonded layer 212 may be between about 1 nm and about 3 nm, preferably between about 2 nm and about 3 nm.

[0036] The reference layer 21 disclosed herein has enhanced SAF stiffness. The magnetoresistive element 2 has low angular error even under high magnetic fields, improved thermal stability, and a low saturation magnetic field H sat This does not affect other magnetic properties of the magnetoresistive element 2, such as an increase in the TMR or the like.

[0037] FIG. 4 shows the magnetic saturation magnetic field H sat 1 is a graph reporting the relationship between the magnetic saturation field H and the thickness of the reference coupled layer 212. The magnetic saturation field H sat The deposition and oxidation may be repeated two to four times in succession. The magnetoresistance element 2 was heat-treated at 310° C. for 90 minutes in a magnetic field of about 1 T.

[0038] In a first configuration (●), the reference bonded layer 212 comprises a single layer of CoFeB alloy with a thickness of about 1.9 nm. In a second configuration (▲), the reference bonded layer 212 is about 1.9 nm thick and comprises a first bonded sublayer 214 of CoFe alloy with a thickness of about 0.5 nm and a second bonded sublayer 215 of CoFeB alloy with a thickness of about 1.4 nm. In a third configuration (★), the reference bonded layer 212 comprises a first bonded sublayer 214 of CoFe alloy with a thickness of about 0.5 nm, a second bonded sublayer 215 of CoFeB alloy with a thickness of about 0.75 nm, an insertion layer 216 of Ta with a thickness of about 0.2 nm, and a third bonded sublayer 217 of CoFeB alloy with a thickness varying between about 0.45 nm and about 0.95 nm.

[0039] Compared to the first and second configurations, in the third configuration the magnetoresistance element 2 has a higher saturation magnetic field H sat Have.

[0040] 5 is a graph reporting the relationship between the resistance area product RA of the magnetoresistive element 2 and the thickness of the reference coupled layer 212. RA was measured for the magnetoresistive element 2 in the first, second, and third configurations described above (in the figure, ●, ▲, and ★, respectively). FIG 5 further reports the relationship between the TMR response of the magnetoresistive element 2 and the thickness of the reference coupled layer 212 for the first, second, and third configurations of the magnetoresistive element 2 (in the figure, ○, △, and ☆, respectively).

[0041] As shown in FIG. 5, the third configuration of magnetoresistive element 2 has a TMR coefficient that is smaller than that observed for the other configurations. The third coupled sub-layer has a thickness of about 0.65 nm, which results in a larger TMR value compared to the first. For the third configuration with layer 217, the TMR is about 30% higher. The third bonding sublayer 217 has a thickness of between about 90% without the insertion layer 216 and about 100% with the insertion layer 216. This results in an increase in TMR of approximately 140%. The present application provides, for example, the following aspects: [Point 1] a fixed reference magnetization (210); a sense ferromagnetic layer (23) having a sense magnetization (230) freely orientable with respect to a reference magnetization (210) in the presence of an external magnetic field; A magnetoresistance element (2) for a two-dimensional magnetic field sensor, comprising a reference ferromagnetic layer (21) having a tunnel barrier layer (22) between the reference ferromagnetic layer (21) and a sense ferromagnetic layer (23), The reference layer (21) comprises a reference coupling layer (213) between a reference pinned layer (211) and a reference coupled layer (212); the reference bonded layer (212) comprises a first bonded sublayer (214) in contact with the reference bonded layer (213), a second bonded sublayer (215) in contact with the first bonded sublayer (214), a third bonded sublayer (217), and an insertion layer (216) between the second bonded sublayer (215) and the third bonded sublayer (217); the insertion layer (216) provides ferromagnetic exchange coupling between the second coupled sublayer (215) and the third coupled sublayer (217); In the magnetoresistance element (2), the thickness of the Ta-containing insertion layer (216) is 0.2 nm, and the thickness of the reference coupled layer (212) is between 1 nm and 5 nm. the reference pinning layer (211) contains a CoFe alloy and has a thickness of 2 nm, the tunnel barrier layer (22) contains Mg, the insertion layer (216) contains Ta, the first coupled sublayer (214) is made of a CoFe alloy and has a thickness of 0.5 nm, the second coupled sublayer (215) is made of a CoFeB alloy and has a thickness of 0.75 nm, and the third coupled sublayer (217) is made of a CoFeB alloy and has a thickness of 0.45 nm to 0.95 nm, wherein the magnetoresistance element (2) is heat-treated at 310° C. for 90 minutes under a magnetic field of about 1 T. [Point 2] The magnetoresistive element according to aspect 1, wherein the insertion layer (216) is amorphous, quasi-amorphous, or nanocrystalline. [Point 3] A magnetoresistive element according to aspect 1 or 2, wherein the first bonded sublayer (214) comprises Co or a CoFe alloy and the second bonded sublayer (215) comprises a CoFeB alloy. [Point 4] A magnetoresistive element according to any one of the preceding aspects, wherein the reference pinned layer (211) may contain Co, Fe, Ni, Cr, V, Si or B, or any combination of these elements. [Point 5] A magnetoresistive element according to any one of the preceding aspects, wherein the second coupled sublayer (215) has a thickness between 1 and 2 times the thickness of the third coupled sublayer (217). [Point 6] A magnetic field sensor for sensing a two-dimensional magnetic field, comprising a magnetoresistance element (2) according to any one of aspects 1 to 5. [Explanation of symbols]

[0042] 2. Magnetoresistance element 21 Ferromagnetic reference layer 210 Reference magnetization 211 Reference pinning layer 212 Reference bound layer 213 Reference binding layer 214 1st coupled sublayer 215 2nd coupled sublayer 216 Insertion Layer 217 3rd coupled sublayer 22 Tunnel Barrier Layer 23 Ferromagnetic sense layer 230 Sense Magnetization 231 First ferromagnetic sense sublayer 232 Second ferromagnetic sense sublayer 233 Non-magnetic sense sublayer 24 Antiferromagnetic layer 25 Overlay 26 Lower layer 27 Seed Layer 60 External Magnetic Field H ex Synthetic antiferromagnetism (SAF) coupling exchange field H k Anisotropic Field H SAT Magnetic saturation field J ex Binding Energy Density RA resistance area product

Claims

1. 1. A method for obtaining a magnetoresistive element for a two-dimensional magnetic field sensor, comprising a ferromagnetic reference layer having a fixed reference magnetization and a sense magnetization that is freely oriented with respect to the reference magnetization in the presence of an external magnetic field, and a tunnel barrier layer between the ferromagnetic reference layer and the ferromagnetic sense layer, comprising: the ferromagnetic reference layer comprises a reference coupling layer between a reference pinned layer and a reference coupled layer; the reference bonded layer comprises a first bonded sublayer adjacent to the reference bonded layer, a second bonded sublayer adjacent to the first bonded sublayer, a third bonded sublayer, and an insertion layer between the second bonded sublayer and the third bonded sublayer; the insertion layer provides ferromagnetic exchange coupling between the second coupled sublayer and the third coupled sublayer; the insertion layer contains Ta and has a thickness of 0.2 nm; the reference pinning layer comprises a CoFe alloy and has a thickness of 2 nm; the tunnel barrier layer contains magnesium oxide; the first bonded sublayer is made of a CoFe alloy and has a thickness of 0.5 nm; the second bonded sublayer is made of a CoFeB alloy and has a thickness of 0.75 nm; the third bonded sublayer is made of a CoFeB alloy and has a thickness of 0.45 nm to 0.95 nm; The method further comprising: forming the ferromagnetic reference layer, the tunnel barrier layer, and the ferromagnetic sense layer; A method for obtaining a magnetoresistive element for a two-dimensional magnetic field sensor, comprising heat treating the magnetoresistive element at 310° C. for 90 minutes in a magnetic field of about 1 T.

2. The method of claim 1, wherein the insertion layer is amorphous, quasi-amorphous or nanocrystalline.

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