Single-substrate full-bridge TMR magnetic field sensor and method of making same

Abstract

The application provides a single-substrate full-bridge TMR magnetic field sensor and a preparation method thereof, and comprises four groups of MTJ devices connected into a full-bridge structure, two groups of MTJ devices on one pair of opposite bridge arms are located in a first region of a substrate, and two groups of MTJ devices on the other pair of opposite bridge arms are located in a second region of the substrate, wherein the two groups of MTJ devices in the first region have a first stack structure, comprising a first pinning layer, a coupling transition layer, a first reference layer, a first barrier layer and a first free layer which are sequentially stacked from bottom to top; the two groups of MTJ devices in the second region have a second stack structure, comprising a second pinning layer, a second reference layer, a second barrier layer and a second free layer which are sequentially stacked from bottom to top. The application can obtain MTJ devices with two different magnetization directions through only one external magnetic field magnetization.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of TMR magnetic field sensor, and particularly relates to a single-substrate full-bridge TMR magnetic field sensor and a preparation method thereof. BACKGROUND

[0002] TMR sensor is a new type of sensor that has been applied in industry in recent years. The sensor uses the tunneling magnetoresistance (TMR) effect of a magnetic tunnel junction (MTJ) multilayer film to detect an external magnetic field. The resistance of the magnetic multilayer film in the TMR sensor changes with the angle and size of the external magnetic field. Compared with the Hall and AMR (Anisotropic Magnetoresistance) sensors that are widely used at present, the TMR sensor has the advantages of high sensitivity, high resistivity, low power consumption, and high resolution, and is the focus of current industry research.

[0003] In the use process of the TMR sensor, temperature drift and zero error need to be considered. People generally use a Wheatstone full-bridge structure. Compared with a single-resistor and reference-resistor half-bridge sensor, the structure has higher sensitivity and good temperature compensation function, and can suppress the output signal drift caused by temperature.

[0004] A typical full-bridge TMR magnetic field sensor structure is shown in Figure 1 Figure 1 A vertical full-bridge TMR magnetic field sensor sensitive to the z-axis is taken as an example. There are four groups of MTJ devices in total. The MTJ devices of each bridge arm are composed of a plurality of magnetic tunnel junctions in series and parallel. The MTJ devices on adjacent bridge arms have opposite output trends to the same magnetic field, that is, the reference layer magnetization directions of the MTJ devices on adjacent bridge arms are opposite. The reference layer magnetization directions of the MTJ devices on one pair of opposite bridge arms are upward, and the reference layer magnetization directions of the MTJ devices on the other pair of opposite bridge arms are downward.

[0005] In the prior art, in order to realize two different magnetization directions on a single substrate, a typical solution is to magnetize the reference layers of the MTJ devices on different bridge arms by a precisely positionable laser annealing device in two times. Each time of laser heating heats only the wafer position corresponding to one group of bridge arms. This method not only increases the complexity of the sensor manufacturing process, but also requires a special annealing device, thereby increasing the cost. SUMMARY

[0006] ​Therefore, the application provides a single-substrate full-bridge TMR magnetic field sensor and a preparation method thereof.

[0007] In a first aspect, the application provides a single-substrate full-bridge TMR magnetic field sensor, comprising: four groups of MTJ devices connected in a full-bridge structure, two groups of MTJ devices on one pair of opposite bridge arms are located in a first region of the substrate, and two groups of MTJ devices on the other pair of opposite bridge arms are located in a second region of the substrate, wherein,

[0008] The two groups of MTJ devices in the first region have a first stack structure, and the first stack structure comprises, from bottom to top, a first pinned layer, a coupling transition layer, a first reference layer, a first barrier layer, and a first free layer.

[0009] The two groups of MTJ devices in the second region have a second stack structure, and the second stack structure comprises, from bottom to top, a second pinned layer, a second reference layer, a second barrier layer, and a second free layer.

[0010] The first pinned layer and the second pinned layer have the same vertical magnetization, the coupling transition layer and the first reference layer have vertical magnetization and the magnetization direction is opposite to that of the first pinned layer, the second reference layer has vertical magnetization and the magnetization direction is the same as that of the second pinned layer, and the first free layer and the second free layer have in-plane magnetization.

[0011] Optionally, the first pinned layer and the second pinned layer are made of the same material, and the material is selected from one or more combinations of MnGa, MnAl, FePt, FePd, and CoTb.

[0012] Optionally, the structure of the coupling transition layer adopts any one of the following structures: Co, Co x Fe 1-x (x>20 at %), [Co / Heavy Metal]n multilayer film, and the heavy metal is one of Pt, Ni, and Pd.

[0013] Optionally, the first reference layer and the second reference layer have the same structure, and the structure adopts any one of the following structures: Co x Fe 1-x (x<20 at %) single layer, Co x Fe 1-x (x<20 at %) / CoFe stack, [Co x Fe 1-x (x<20 at %) / CoFeB]n multilayer film, [Fe / CoFeB]n multilayer film, [Co x Fe1-x (x<20at%) / spacer / CoFeB]n multilayer film, wherein the spacer is one of Mo, W, Ta.

[0014] Optionally, the first free layer and the second free layer are of the same structure, which is any one of CoFeB single layer, NiFe single layer, CoFeB / NiFe stack.

[0015] In a second aspect, the present application provides a method for manufacturing a single-substrate full-bridge TMR magnetic field sensor, which comprises:

[0016] providing a substrate, and forming a pinning layer film, a coupling transition layer film and a protection layer film on the substrate in sequence;

[0017] performing patterning definition on the protection layer film to form a first region and a second region;

[0018] removing the protection layer film and the coupling transition layer film in the second region;

[0019] removing the protection layer film in the first region;

[0020] continuing to deposit a multilayer MTJ film, which comprises at least a reference layer film, a barrier layer film and a free layer film from bottom to top, covering the first region and the second region;

[0021] forming an MTJ device with a first stack structure in the first region and an MTJ device with a second stack structure in the second region, wherein the first stack structure comprises a first pinning layer, a coupling transition layer, a first reference layer, a first barrier layer and a first free layer stacked in sequence from bottom to top, and the second stack structure comprises a second pinning layer, a second reference layer, a second barrier layer and a second free layer stacked in sequence from bottom to top;

[0022] applying an external magnetic field to initialize, so that the first pinning layer and the second pinning layer have the same vertical magnetization, the coupling transition layer and the first reference layer have vertical magnetization and the magnetization direction is opposite to that of the first pinning layer, the second reference layer has vertical magnetization and the magnetization direction is the same as that of the second pinning layer, and the first free layer and the second free layer have in-plane magnetization.

[0023] Optionally, after removing the protection layer film in the first region, the method further comprises:

[0024] performing surface treatment by hydrogen plasma to remove potential oxide layer on the surface.

[0025] Optionally, the material of the pinning layer thin film is selected from a combination of one or more of MnGa, MnAl, FePt, FePd, CoTb.

[0026] Optionally, the structure of the coupling transition layer thin film adopts any one of Co, Co x Fe 1-x (x>20 at%) and [Co / Heavy Metal]n multilayer film, wherein the heavy metal is one of Pt, Ni and Pd.

[0027] Optionally, the protective layer thin film is a Ti thin film with a thickness of 1-3 nm.

[0028] The single-substrate full-bridge TMR magnetic field sensor and the preparation method thereof provided by the application form a MTJ device with a first stack structure in a first region and a MTJ device with a second stack structure in a second region, the first stack structure comprises a first pinning layer, a coupling transition layer, a first reference layer, a first barrier layer and a first free layer stacked in turn from bottom to top, and the second stack structure comprises a second pinning layer, a second reference layer, a second barrier layer and a second free layer stacked in turn from bottom to top; only one external magnetic field magnetization is needed to obtain MTJ devices with two different magnetization directions, the preparation process is simplified, and the cost is reduced. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 A schematic diagram of a vertical full-bridge TMR magnetic field sensor sensitive to the z-axis in the prior art;

[0030] Figures 2A to 2F A schematic diagram of the preparation method of the single-substrate full-bridge TMR magnetic field sensor in an embodiment of the application;

[0031] Figure 3 A schematic diagram of the principle of interface coupling varying with the CoFe component. x Fe 1-x A schematic diagram of the principle of interface coupling varying with the CoFe component. DETAILED DESCRIPTION

[0032] To make the objectives, technical solutions and advantages of the embodiments of the application clearer, the technical solutions in the embodiments of the application will be described below in connection with the drawings of the embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the application.

[0033] It should be noted that the terms "first", "second", and the like in the description and in the claims of the present application and the above-described accompanying drawings are used to distinguish similar objects, and do not necessarily indicate a specific order or sequence. It should be understood that the data thus used can be interchanged under appropriate circumstances, so that the embodiments of the present application described herein can be implemented. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device including a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but can include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0034] Some embodiments of the present application will be described in detail below with reference to the accompanying drawings. The following examples and features in the examples can be combined with each other without conflict.

[0035] An embodiment of the present application proposes a preparation method of a single-substrate full-bridge TMR magnetic field sensor, referring to Figures 2A~2F The preparation method comprises the following steps:

[0036] As shown in Figure 2A , a substrate (also referred to as a wafer) is provided, and the substrate 10 has a bottom metal interconnection structure (not shown) formed therein for subsequent interconnection of MTJ devices. A pinning layer film 11, a coupling transition layer film 12 and a protective layer film 13 are sequentially formed on the substrate 10. According to an embodiment of the present application, the material of the pinning layer film 11 is selected from one or more combinations of MnGa, MnAl, FePt, FePd and CoTb. The structure of the coupling transition layer film 12 adopts any one of the following: Co, CoxFe1-x (x>20 at %), [Co / Heavy Metal]n multilayer film, and the heavy metal is one of Pt, Ni and Pd. In some embodiments, a layer of Co can also be coated on the [Co / Heavy Metal]n multilayer film to improve its properties. The basic principle is that the layer in direct contact with the pinning layer film 11 is a magnetic layer with a higher Co content. The protective layer film 13 is a Ti film with a thickness of 1-3 nm.

[0037] Further, after the pinning layer film 11 is formed, an annealing process is performed to improve the crystal structure of the pinning layer film 11.

[0038] Then the film stack structure of the MTJ reference layer below to the substrate is constructed. As shown in Figure 2B , photoresist (PR) is spin-coated, and the protective layer film 13 is patterned and defined by a photolithography process to form a first region and a second region.

[0039] As shown in Figure 2CAs shown, the protective layer film 13 and the coupling transition layer film 12 in the second region are removed. Here, we exemplify the removal of the entire coupling transition layer film 12 in the second region through an etching process, followed by resist removal and cleaning after etching. It should be noted that in some embodiments, a portion of the coupling transition layer film 12 may be retained and completely removed in subsequent processes.

[0040] like Figure 2D As shown, the wafer is baked, and then the protective layer film 13 of the first region is removed by plasma bombardment or wet etching, ultimately leaving only the coupling transition layer film 12 of the first region. It is understood that if there are remnants of the coupling transition layer film 12 of the second region from previous etching processes, the coupling transition layer film 12 of the second region will be completely removed during or after the removal of the protective layer film 13 of the first region. Preferably, according to an embodiment of the present invention, after removing the protective layer film of the first region, surface treatment is performed using hydrogen plasma (H+ ions) to further remove any potential oxide layer on the surface.

[0041] Then as Figure 2E As shown, multiple MTJ films are deposited, including at least a reference layer film 14, a barrier layer film 15, and a free layer film 16 from bottom to top, covering the first and second regions. Preferably, according to an embodiment of the present invention, after depositing the multiple MTJ films, an annealing process is performed to crystallize each MTJ film to obtain high TMR. According to an embodiment of the present invention, the reference layer film 14 is any one of the following: Co x Fe 1-x (x<20at%) monolayer, Co x Fe 1-x (x<20at%) / CoFe stack, [Co] x Fe 1-x (x<20at%) / CoFeB]n multilayer film, [Fe / CoFeB]n multilayer film, [Co x Fe 1-x [x<20at%) / spacer layer / CoFeB]n multilayer film, wherein the spacer layer is one of Mo, W, or Ta. The barrier layer film 15 is one of MgO, MgAlO, or Al2O3, with a thickness between 1.0 and 2.0 nm. The free layer film 16 is any one of the following: CoFeB monolayer, NiFe monolayer, or CoFeB / NiFe stack.

[0042] Then as Figure 2FAs shown, the MTJ device with a first stack structure is formed in the first region and the MTJ device with a second stack structure is formed in the second region by photolithography and etching processes, the first stack structure includes the first pinned layer 111, the coupling transition layer 121, the first reference layer 141, the first barrier layer 151 and the first free layer 161 stacked in order from bottom to top, and the second stack structure includes the second pinned layer 112, the second reference layer 142, the second barrier layer 152 and the second free layer 162 stacked in order from bottom to top.

[0043] It is easily understood that the substrate 10 does not need to be etched, and the layers of thin films are etched from top to bottom, if necessary, a suitable hard mask layer is deposited. The first pinned layer 111, the coupling transition layer 121, the first reference layer 141, the first barrier layer 151 and the first free layer 161 are obtained by etching the pinned layer thin film 11, the coupling transition layer thin film 12, the reference layer thin film 14, the barrier layer thin film 15 and the free layer thin film 16 in the first region. The second pinned layer 112, the second reference layer 142, the second barrier layer 152 and the second free layer 162 are obtained by etching the pinned layer thin film 11, the reference layer thin film 14, the barrier layer thin film 15 and the free layer thin film 16 in the second region.

[0044] After the MTJ device is formed, an external magnetic field is applied for initialization, so that the first pinned layer 111 and the second pinned layer 112 have the same vertical magnetization, the coupling transition layer 121 and the first reference layer 141 have vertical magnetization and the magnetization direction is opposite to that of the first pinned layer 111, the second reference layer 142 has vertical magnetization and the magnetization direction is the same as that of the second pinned layer 112, and the first free layer 161 and the second free layer 162 have in-plane magnetization, which can be the same or different.

[0045] In addition, in order to realize the interconnection of the MTJ device, it is necessary to form a top metal interconnection structure on the top, cooperate with the bottom metal interconnection structure in the substrate 10, so that the MTJ device in the first region constitutes two groups of MTJ devices on the opposite bridge arms, and the MTJ device in the second region constitutes two groups of MTJ devices on the other pair of opposite bridge arms, and is connected into a full-bridge structure.

[0046] The preparation method of the single-substrate full-bridge TMR magnetic field sensor provided by the embodiment of the application comprises the following steps: forming an MTJ device with a first stack structure in a first region and forming an MTJ device with a second stack structure in a second region, the first stack structure comprising a first pinned layer, a coupling transition layer, a first reference layer, a first barrier layer and a first free layer which are sequentially stacked from bottom to top, and the second stack structure comprising a second pinned layer, a second reference layer, a second barrier layer and a second free layer which are sequentially stacked from bottom to top; when an external magnetic field is applied (for example, upward), the magnetization directions of the first pinned layer and the second pinned layer will be consistent with the external field (upward), the MTJ device in the first region exhibits anti-ferromagnetic coupling because the coupling transition layer in contact with the first pinned layer has a relatively high Co content (> 20 at %), and finally the reference layer of the MTJ device in the first region generates a magnetization direction opposite to that of the first pinned layer. The MTJ device in the second region exhibits ferromagnetic coupling because the second reference layer in contact with the second pinned layer has a relatively low Co content (< 20 at %), and finally the reference layer of the MTJ device in the second region generates a magnetization direction same as that of the second pinned layer. Therefore, only one external magnetic field magnetization is needed to obtain MTJ devices with two different magnetization directions, the process is simple, and the cost is reduced.

[0047] In another aspect, the embodiment of the application provides a single-substrate full-bridge TMR magnetic field sensor, comprising four groups of MTJ devices connected in a full-bridge structure, two groups of MTJ devices on one pair of opposite bridge arms are located in a first region of a substrate, and two groups of MTJ devices on the other pair of opposite bridge arms are located in a second region of the substrate. For reference Figure 2F The device structure shown, the two groups of MTJ devices in the first region have a first stack structure, and the first stack structure comprises a first pinned layer 111, a coupling transition layer 121, a first reference layer 141, a first barrier layer 151 and a first free layer 161 which are sequentially stacked from bottom to top; the two groups of MTJ devices in the second region have a second stack structure, and the second stack structure comprises a second pinned layer 112, a second reference layer 142, a second barrier layer 152 and a second free layer 162 which are sequentially stacked from bottom to top;

[0048] The first pinned layer 111 and the second pinned layer 112 have the same vertical magnetization, the coupling transition layer 121 and the first reference layer 141 both have vertical magnetization and the magnetization directions thereof are opposite to that of the first pinned layer 111, the second reference layer 142 has vertical magnetization and the magnetization direction thereof is the same as that of the second pinned layer 112, and the first free layer 161 and the second free layer 162 have in-plane magnetization, and the magnetization directions thereof can be the same or different.

[0049] According to an embodiment of the present application, the first pinning layer 111 and the second pinning layer 112 are made of the same material, which is selected from one or more of MnGa, MnAl, FePt, FePd, CoTb.

[0050] The following is described by taking MnGa as an example. MnGa is a material with super-strong PMA (Perpendicular Magnetic anisotropy). In addition, MnGa and Co x Fe 1-x The interface coupling between MnGa and CoFe changes from FM to AFM with the change of CoFe component. The specific principle can be referred to in Figure 3 When the percentage of Co atoms is greater than 20%, the coupling is AFM, and when the percentage of Co atoms is less than 20%, the coupling is FM.

[0051] Based on the above principle, the structure of the coupling transition layer 121 can be any of the following: Co, CoxFe1-x(x>20 at%), [Co / heavy metal]n multilayer, and the heavy metal is one of Pt, Ni, and Pd. In some embodiments, a layer of Co can be further coated on the [Co / heavy metal]n multilayer to improve its properties. The basic principle is that the layer in direct contact with the first pinning layer 111 is a magnetic layer with a high Co content. Under the action of the coupling transition layer 121, the magnetization direction of the first reference layer 141 is opposite to that of the first pinning layer 111.

[0052] The first reference layer 141 and the second reference layer 142 can be any of the following: Co x Fe 1-x (x<20 at%) single layer, Co x Fe 1-x (x<20 at%) / CoFe stack, [Co x Fe 1-x (x<20 at%) / CoFeB]n multilayer, [Fe / CoFeB]n multilayer, [Co x Fe 1-x (x<20 at%) / spacer / CoFeB]n multilayer, wherein the spacer is one of Mo, W, and Ta.

[0053] The first barrier layer 151 and the second barrier layer 152 are one of MgO, MgAlO, and Al2O3, and the thickness is between 1.0-2.0 nm.

[0054] The first free layer 161 and the second free layer 162 can be any of the following: CoFeB single layer, NiFe single layer, CoFeB / NiFe stack.

[0055] A preferred embodiment is given, the first pinning layer 111 and the second pinning layer 112 adopt MnGa (10 nm). The coupling transition layer 121 adopts a [Co / Pt]4 multilayer film, that is, Co (0.3 nm) / Pt (0.6 nm) is repeated 4 times, preferably a Co (0.2-1 nm) is covered on the top, and the value in the bracket represents the thickness.

[0056] The material of the first reference layer 141 and the second reference layer 142 is Fe / CoFeB and the like grown in sequence, wherein the Fe layer is close to MnGa, for example, Fe (0.5 nm) / CoFeB (1.0 nm) / Mo (0.2 nm) / CoFeB (1.0 nm).

[0057] The material of the first barrier layer 151 and the second barrier layer 152 is MgO, and the thickness is between 1.0-2.0 nm.

[0058] The material of the first free layer 161 and the second free layer 162 is CoFeB / NiFe, for example, CoFeB (2 nm) / NiFe (20 nm).

[0059] The single-substrate full-bridge TMR magnetic field sensor provided by the application is based on a MnGa series material system, a coupling transition layer is introduced, two MTJ devices with different magnetization directions can be obtained only by one external magnetic field magnetization, the preparation process is simplified, and the cost is reduced.

[0060] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement to part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A single substrate full-bridge TMR magnetic field sensor, characterized in that, The method comprises: four groups of MTJ devices connected into a full-bridge structure, two groups of MTJ devices on one pair of opposite bridge arms are located in a first region of a substrate, and two groups of MTJ devices on another pair of opposite bridge arms are located in a second region of the substrate, wherein, the two groups of MTJ devices in the first region have a first stack structure, the first stack structure comprises a first pinned layer, a coupling transition layer, a first reference layer, a first barrier layer and a first free layer stacked from bottom to top, the coupling transition layer is a magnetic layer containing Co and exhibiting anti-ferromagnetic coupling, so that the first reference layer and the first pinned layer have opposite magnetization directions; the two groups of MTJ devices in the second region have a second stack structure, the second stack structure comprises a second pinned layer, a second reference layer, a second barrier layer and a second free layer stacked from bottom to top; wherein the first pinned layer and the second pinned layer have the same vertical magnetization, the coupling transition layer and the first reference layer have vertical magnetization and opposite magnetization directions to the first pinned layer, the second reference layer has vertical magnetization and the same magnetization direction as the second pinned layer, and the first free layer and the second free layer have in-plane magnetization.

2. The single-substrate full-bridge TMR magnetic field sensor of claim 1, wherein, The first pinned layer and the second pinned layer are the same material, and the material is selected from one or more combinations of MnGa, MnAl, FePt, FePd and CoTb.

3. The single-substrate full-bridge TMR magnetic field sensor of claim 1, wherein, The structure of the coupling transition layer adopts any one of the following: Co, Co x Fe 1-x , [Co / heavy metal]n multilayer film, the heavy metal is one of Pt, Ni, Pd, and x>20at%.

4. The single-substrate full-bridge TMR magnetic field sensor of claim 1, wherein, The first reference layer and the second reference layer have the same structure, which is any one of the following: Co x Fe 1-x single layer, Co x Fe 1-x / CoFe stack, [Co x Fe 1-x / CoFeB]n multilayer film, [Fe / CoFeB]n multilayer film, [Co x Fe 1-x / spacer layer / CoFeB]n multilayer film, wherein the spacer layer is one of Mo, W, Ta, and wherein x < 20 at%.

5. The single-substrate full-bridge TMR magnetic field sensor of claim 1, wherein, The first free layer and the second free layer have the same structure, and the structure adopts any one of the following: CoFeB monolayer, NiFe monolayer, CoFeB / NiFe laminated layer.

6. A method of fabricating a single substrate full-bridge TMR magnetic field sensor, characterized by, The method comprises: providing a substrate, the substrate has a substrate, a pinned layer film, a coupling transition layer film and a protective layer film are formed on the substrate in sequence, the coupling transition layer film is a magnetic layer film containing Co and exhibiting anti-ferromagnetic coupling; defining a pattern on the protective layer film to form a first region and a second region; removing the protective layer film and the coupling transition layer film in the second region; removing the protective layer film in the first region; continuing to deposit a multi-layer MTJ film, which at least includes a reference layer film, a barrier layer film and a free layer film from bottom to top, covering the first region and the second region; forming MTJ devices with a first stack structure in the first region and MTJ devices with a second stack structure in the second region, the first stack structure comprises a first pinned layer, a coupling transition layer, a first reference layer, a first barrier layer and a first free layer stacked from bottom to top, and the second stack structure comprises a second pinned layer, a second reference layer, a second barrier layer and a second free layer stacked from bottom to top; applying an external magnetic field for initialization, so that the first pinned layer and the second pinned layer have the same vertical magnetization, the coupling transition layer and the first reference layer have vertical magnetization and opposite magnetization directions to the first pinned layer, the second reference layer has vertical magnetization and the same magnetization direction as the second pinned layer, and the first free layer and the second free layer have in-plane magnetization.

7. The method of claim 6, wherein, After removing the protective layer film of the first region, further comprising: Surface treatment is performed using hydrogen plasma to remove potential surface oxidation layers.

8. The method of claim 6, wherein, The material of the pinning layer film is selected from a combination of one or more of MnGa, MnAl, FePt, FePd, and CoTb.

9. The method of claim 6, wherein, The structure of the coupling transition layer thin film adopts any one of the following: Co, Co x Fe 1-x , [Co / heavy metal]n multilayer film, the heavy metal is one of Pt, Ni, Pd, and x>20at%.

10. The method of claim 6, wherein, The protective layer film is a Ti film with a thickness of 1-3 nm.

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