A magnetic tunnel junction and methods of making and using the same

Abstract

This invention relates to the field of magnetic electronic devices, and more particularly to a magnetic tunnel junction, its fabrication method, and its applications. The magnetic tunnel junction includes: a lower electrode layer, a tunneling barrier layer, and an upper electrode layer; the tunneling barrier layer is disposed between the upper and lower electrode layers; wherein the tunneling barrier layer includes a self-supporting hafnium zirconium oxide film; the thickness of the self-supporting hafnium zirconium oxide film is 1-3 nm. The fabrication of this magnetic tunnel junction includes: firstly, growing an ultrathin LSMO / HZO bilayer structure on a substrate using PLD; utilizing LSMO as a sacrificial layer that can be selectively removed by a mixed solution of HCl and KI to release HZO in a self-supporting form; then, attaching the HZO to an FGT electrode to finally form the magnetic tunnel junction. The magnetic tunnel junction provided by this invention exhibits a tunneling magnetoresistance ratio (TMR) of approximately 140% at 2 K, indicating that the combination of this ultrathin ferroelectric barrier and the two-dimensional ferromagnetic electrode can achieve significant spin-polarized tunneling.

Description

Technical Field

[0001] This invention relates to the field of magnetic electronic devices, and more particularly to a magnetic tunnel junction, its preparation method, and its application. Background Technology

[0002] Magnetic tunnel junctions (MTJs) are the core structure of spintronic devices, widely used in applications such as magnetic random access memory (MRAM) and magnetic sensing. A typical MTJ consists of two ferromagnetic electrodes and a tunneling barrier layer in between. The resistance differs when the magnetization directions of the two electrodes are parallel or antiparallel, exhibiting the tunnel magnetoresistance effect (TMR).

[0003] In recent years, two-dimensional ferromagnets based on layered van der Waals materials (such as Fe3GeTe2, or FGT) have been considered important candidates for realizing ultrathin, integrable spin devices due to their mechanical exfoliation, stackability, and atomically flat interfaces. However, two-dimensional ferromagnets are generally sensitive to high-temperature oxidizing environments, plasma, and chemical contamination, making it difficult to directly deposit high-quality oxide barrier layers (especially ferroelectric oxides that require high-temperature crystallization / annealing) on ​​their surfaces. This can easily lead to interface damage, magnetic degradation, and poor device consistency.

[0004] Hafnium zirconium oxide (Hf 0.5 Zr 0.5 O2 (HZO) is a type of ferroelectric material compatible with CMOS processes. To maintain both ferroelectricity and low defect density at the tunneling scale (approximately 1-3 nm), epitaxial or preferentially oriented growth on a lattice-matched substrate is typically required, while avoiding damage to the ultrathin film during subsequent processes. In existing methods, HZO is often grown directly on rigid substrates or metal electrodes; however, combining it with mechanically exfoliated two-dimensional ferromagnetic electrodes often requires complex surface treatments, low-temperature deposition, or the introduction of intermediate buffer layers, resulting in barrier thicknesses that are difficult to achieve on the order of 2 nm and insufficient interface controllability.

[0005] Therefore, obtaining a self-supporting HZO ultrathin barrier with a thickness of about 2nm is of great significance. Summary of the Invention

[0006] This invention provides a magnetic tunnel junction, its preparation method, and its application, wherein HZO is a self-supporting ferroelectric tunneling barrier layer with a thickness of about 2 nm.

[0007] To solve the above-mentioned technical problems, the present invention provides the following technical solution: This invention provides a magnetic tunnel junction, comprising: a lower electrode layer, a tunneling barrier layer, and an upper electrode layer; wherein the tunneling barrier layer is disposed between the upper electrode layer and the lower electrode layer; The tunneling barrier layer includes a self-supporting hafnium zirconium oxide film; The thickness of the self-supporting hafnium zirconium oxide film is 1~3nm.

[0008] In some specific embodiments, the overlapping region of the lower electrode layer and the upper electrode layer in the vertical projection direction is a junction region, and the area of ​​the junction region is 140~160μm. 2 .

[0009] In some specific embodiments, the lower electrode layer and the upper electrode layer each independently comprise a layered two-dimensional ferromagnetic material.

[0010] In some specific embodiments, the layered two-dimensional ferromagnetic material includes Fe3GeTe2.

[0011] In some specific embodiments, the thickness of the lower electrode layer and the upper electrode layer are each independently 3~100nm.

[0012] In some specific embodiments, the hafnium zirconium oxide in the self-supporting hafnium zirconium oxide film includes Hf 0.5 Zr 0.5 O2.

[0013] A second aspect of the present invention also provides a method for preparing the above-mentioned magnetic tunnel junction, comprising the following steps: A perovskite conductive oxide sacrificial layer and a hafnium zirconium oxide layer are sequentially grown on a substrate by pulsed laser deposition. Polymethyl methacrylate was spin-coated onto the surface of the hafnium zirconium oxide and then subjected to heat treatment. The heat-treated sample was immersed in a mixed solution of HCl and KI to etch the perovskite conductive oxide sacrificial layer, resulting in a hafnium zirconium oxide film with a polymethyl methacrylate layer. A self-supported hafnium zirconium oxide film with a polymethyl methacrylate layer is transferred to the lower electrode layer, the polymethyl methacrylate layer is removed to form a self-supported hafnium zirconium oxide film on the lower electrode layer, and then an upper electrode layer is formed on the self-supported hafnium zirconium oxide film to obtain a magnetic tunnel junction.

[0014] In some specific embodiments, the thickness of the perovskite conductive oxide sacrificial layer is 10~50 nm.

[0015] In some specific embodiments, the perovskite conductive oxide sacrificial layer includes La 0.67 Sr 0.33 MnO3.

[0016] In some specific embodiments, the conditions for pulsed laser deposition to grow the perovskite conductive oxide sacrificial layer are: temperature 750~850℃, oxygen partial pressure 90~110 mTorr, and energy density 1~1.5 J / cm³. 2 .

[0017] In some specific embodiments, the conditions for pulsed laser deposition growth of hafnium zirconium oxide are: temperature of 900~950℃, oxygen partial pressure of 140~160 mTorr, and energy density of 1~1.5 J / cm³. 2 .

[0018] In some specific embodiments, the temperature of the heat treatment is 120~150℃, and the heat treatment time is 3~5 minutes.

[0019] In some specific embodiments, the concentration of HCl in the mixed solution is 0.5~1.5 mol / L, and the concentration of KI is 0.002~0.05 mol / L.

[0020] In some specific embodiments, the etching temperature is 10~30℃ and the etching time is 6~24h.

[0021] In some specific embodiments, the substrate includes a SrTiO3 single crystal substrate.

[0022] A third aspect of the present invention also provides an application of the above-mentioned magnetic tunnel junction in a two-dimensional spin device research platform, a ferroelectric-spin coupled multi-state storage unit, an electrically controllable spin filter, or a magnetic sensor device.

[0023] Compared with the prior art, the present invention has the following beneficial effects: (1) The ultrathin barrier still maintains ferroelectricity: HZO with a thickness of 1~3nm can obtain a reversible ferroelectric polarization signal through PUND (Positive-Up-Negative-Down) pulse test, indicating that it still has ferroelectric switching characteristics at the tunneling thickness scale.

[0024] (2) Minimal interface damage and compatibility with two-dimensional magnets: HZO completes high-quality PLD growth and structural characterization on a rigid substrate (XRD / XRR confirms crystal quality and thickness), and then transfers in a self-supporting manner, avoiding direct high-temperature oxide deposition on the FGT surface, thereby reducing damage to the FGT magnetism and interface.

[0025] (3) Achieving a high TMR: The assembled FGT / HZO / FGT device was measured to have a tunneling magnetoresistance ratio (TMR) of about 140% in PPMS at 2K, which verifies that the combination of the ultrathin ferroelectric barrier and the two-dimensional ferromagnetic electrode can achieve significant spin polarization tunneling. Attached Figure Description

[0026] The above and other objects, features, and advantages of the invention will be apparent from the following description of preferred embodiments illustrating the gist of the invention and its use, and the accompanying drawings, in which: Figure 1 This is a schematic cross-sectional view of the magnetic tunnel junction in Example 1.

[0027] Figure 2 The images shown are actual pictures of the magnetic tunnel junction in Example 1, where (a) to (d) are actual pictures at different magnifications.

[0028] Figure 3 This is a physical image of the Pd / Au bottom electrode and the lower FGT of the magnetic tunnel junction in Example 1.

[0029] Figure 4 The image shows the XRD pattern of the LSMO / HZO thin film in Example 1.

[0030] Figure 5 The image shows the XRR curve of the LSMO / HZO thin film in Example 1.

[0031] Figure 6 The polarization curves of the HZO thin film in Example 1 are obtained from the PUND test.

[0032] Figure 7 This is a photograph of the self-supporting HZO film released in deionized water in Example 1.

[0033] Figure 8 This is a physical image of the self-supporting HZO transferred to the target substrate in Example 1.

[0034] Figure 9 This is a physical diagram of the process in Example 1 where the upper FGT is transferred to cause the upper and lower FGTs to overlap in a predetermined area to form a junction.

[0035] Figure 10 The Pd / Au top electrode was prepared in Example 1.

[0036] Figure 11 The TMR of the magnetic tunnel junction in Example 1 is shown below; where (a) is the result of the first test, (b) is the result of the second test, (c) is calculated from (a), and (d) is calculated from (b). Detailed Implementation

[0037] The present invention will be described below through specific embodiments. Those skilled in the art will understand that the specific embodiments described below are for illustrative purposes only and do not limit the scope of the invention in any way. Furthermore, in the following embodiments, unless otherwise specified, the reagents and equipment used are commercially available. If specific processing conditions and methods are not explicitly described in the following embodiments, conditions and methods known in the art can be used for processing.

[0038] This invention provides a magnetic tunnel junction, comprising: a lower electrode layer, a tunneling barrier layer, and an upper electrode layer; wherein the tunneling barrier layer is disposed between the upper electrode layer and the lower electrode layer; The tunneling barrier layer includes a self-supporting hafnium zirconium oxide film; The thickness of the self-supporting hafnium zirconium oxide film is 1~3nm.

[0039] The magnetic tunnel junction of the present invention includes upper and lower electrode layers and a tunneling barrier layer disposed between the upper and lower electrode layers, wherein the thickness of the self-supporting hafnium zirconium oxide film is 1~3 nm. The 1~3 nm self-supporting hafnium zirconium oxide film can obtain a reversible ferroelectric polarization signal through PUND (Positive-Up-Negative-Down) pulse testing, indicating that it still has ferroelectric switching characteristics at the tunneling thickness scale.

[0040] In some embodiments, the thickness of the self-supporting hafnium zirconium oxide film can be 1 nm, 1.3 nm, 1.5 nm, 1.8 nm, 2 nm, 2.3 nm, 2.5 nm, 2.8 nm, and 3 nm, etc.

[0041] In some embodiments, the overlapping region of the lower electrode layer and the upper and lower electrode layers in the vertical projection direction is a junction region, and the area of ​​the junction region is 140~160μm. 2 .

[0042] In some embodiments, the lower electrode layer and the upper electrode layer each independently comprise a layered two-dimensional ferromagnetic material.

[0043] In some embodiments, the layered two-dimensional ferromagnetic material comprises Fe3GeTe2 (FGT).

[0044] In some embodiments, the thickness of the lower electrode layer and the upper electrode layer are each independently 3~100 nm.

[0045] In some embodiments, the hafnium zirconium oxide in the self-supporting hafnium zirconium oxide film includes Hf 0.5 Zr 0.5 O2 (HZO).

[0046] In some embodiments, for using the magnetic tunnel junction for electrical transport testing, the method further includes: a lower electrode layer connected to a metal electrode, and an upper electrode layer connected to a metal electrode; the metal electrode includes a Pd / Au electrode.

[0047] A second aspect of the present invention also provides a method for preparing the above-mentioned magnetic tunnel junction, comprising the following steps: A perovskite conductive oxide sacrificial layer and a hafnium zirconium oxide layer are sequentially grown on a substrate by pulsed laser deposition. Polymethyl methacrylate (PMMA) was spin-coated onto the surface of the hafnium zirconium oxide and then subjected to heat treatment. The heat-treated sample was immersed in a mixed solution of HCl and KI to etch the perovskite conductive oxide sacrificial layer, resulting in a hafnium zirconium oxide film with a polymethyl methacrylate layer. A self-supported hafnium zirconium oxide film with a polymethyl methacrylate layer is transferred to the lower electrode layer, the polymethyl methacrylate layer is removed to form a self-supported hafnium zirconium oxide film on the lower electrode layer, and then an upper electrode layer is formed on the self-supported hafnium zirconium oxide film to obtain a magnetic tunnel junction.

[0048] In some embodiments, the thickness of the perovskite conductive oxide sacrificial layer is 10~50 nm.

[0049] In some embodiments, the perovskite conductive oxide sacrificial layer includes La 0.67 Sr 0.33 MnO3 (LSMO).

[0050] In some embodiments, the conditions for pulsed laser deposition to grow the perovskite conductive oxide sacrificial layer are: temperature 750~850℃, oxygen partial pressure 90~110 mTorr, and energy density 1~1.5 J / cm³. 2 .

[0051] In some embodiments, the conditions for pulsed laser deposition growth of hafnium zirconium oxide are: temperature of 900~950℃, oxygen partial pressure of 140~160 mTorr, and energy density of 1~1.5 J / cm³. 2 .

[0052] In some embodiments, the temperature of the heat treatment is 120~150°C, and the time of the heat treatment is 3~5 minutes.

[0053] In some embodiments, the concentration of HCl in the mixed solution is 0.5~1.5 mol / L, and the concentration of KI is 0.002~0.05 mol / L.

[0054] In this invention, the sacrificial layer gradually dissolves during the etching process, thereby achieving the removal of the sacrificial layer.

[0055] In some embodiments, the etching temperature is 10~30°C and the etching time is 6~24h.

[0056] In some embodiments, the method of removing the polymethyl methacrylate layer includes: removing the polymethyl methacrylate layer with acetone.

[0057] In this invention, the upper and lower electrode layers can be obtained by means of mechanical peeling or other methods. In some embodiments, the layered two-dimensional ferromagnetic material Fe3GeTe2 is obtained by mechanically peeling off a bulk Fe3GeTe2 single crystal.

[0058] In some embodiments, the substrate comprises a SrTiO3 single crystal substrate.

[0059] In this invention, when using the magnetic tunnel junction for electrical transport testing, the metal electrode can be prepared using conventional techniques in the art, such as photolithography and vapor deposition.

[0060] As an example, the fabrication of a magnetic tunnel junction includes the following steps: (1) Preparation of bottom metal electrode Using a Si substrate as the support substrate, a bottom metal electrode pattern is photolithographically patterned on the substrate using laser direct writing lithography with photoresist. Then, a Pd layer and an Au layer are deposited sequentially using a thermal evaporation method. After the evaporation is completed, the obtained sample is placed in acetone for a lift-off process to remove the photoresist, resulting in a patterned Pd / Au bottom metal electrode on the support substrate. (2) Mechanical stripping and transfer of the lower FGT The bulk Fe3GeTe2 single crystal was mechanically exfoliated using PDMS to obtain thin FGT nanosheets. The thin FGT nanosheets on the PDMS were aligned with a pre-prepared Pd / Au bottom metal electrode and slowly lowered to bring the thin FGT nanosheets into contact with the bottom metal electrode. The sample was then heated to release the FGT nanosheets and allow them to adhere firmly to the bottom metal electrode, forming the lower electrode FGT ferromagnetic layer. (3) Preparation and transfer of self-supporting HZO ultrathin films A perovskite conductive oxide sacrificial layer and a hafnium zirconium oxide were sequentially grown on a SrTiO3 single crystal substrate by pulsed laser deposition. Polymethyl methacrylate (PMMA) was spin-coated onto the surface of the hafnium zirconium oxide and then subjected to heat treatment. The resulting sample after heat treatment was immersed in a mixed solution of HCl and KI to etch the perovskite conductive oxide sacrificial layer, and then immersed in deionized water to obtain a hafnium zirconium oxide film with a PMMA layer. The self-supporting hafnium zirconium oxide film with a PMMA layer in deionized water was then transferred to the lower electrode layer, and the PMMA layer was removed to form a self-supporting hafnium zirconium oxide film on the lower electrode layer. (4) Mechanical stripping and transfer of the upper FGT Mechanical exfoliation of bulk Fe3GeTe2 single crystals using PDMS was used to obtain thin FGT nanosheets. The thin FGT nanosheets on PDMS were aligned with the pre-lower electrode FGT ferromagnetic layer so that the upper FGT and the lower FGT overlapped to form a junction region. Then, heat treatment was performed to form an FGT / HZO / FGT sandwich structure. (5) Preparation of the top metal electrode The top electrode pattern is created by laser direct writing exposure development, ensuring that it only contacts the upper FGT layer. Then, Pd and Au are deposited sequentially by thermal evaporation. Finally, acetone lift-off is performed to remove the photoresist, resulting in the top metal electrode.

[0061] It should be noted that the above steps are merely one specific implementation method for achieving the technical solution of the present invention. Those skilled in the art can make equivalent substitutions or conventional adjustments to the specific process parameters, material selection, and implementation methods of each step without departing from the technical concept of the present invention.

[0062] For example, the metal electrode material is not limited to Pd / Au, but can also be other conductive metals or combinations thereof; the transfer method of the two-dimensional material is not limited to PDMS-assisted transfer; the patterning process is not limited to laser direct writing lithography, but can also be ultraviolet lithography or electron beam lithography.

[0063] A third aspect of the present invention also provides an application of the above-mentioned magnetic tunnel junction in a two-dimensional spin device research platform, a ferroelectric-spin coupled multi-state storage unit, an electrically controllable spin filter, or a magnetic sensor device.

[0064] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings and embodiments. The embodiments of this application are only examples, and all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0065] Example 1 A schematic cross-sectional structure of a magnetic tunnel junction is shown below. Figure 1 Actual product image as shown Figure 2 As shown: From bottom to top, the layers are: a lower electrode FGT ferromagnetic layer, a self-supporting HZO ultrathin ferroelectric barrier layer, and an upper electrode FGT ferromagnetic layer. The upper and lower FGT ferromagnetic layers are connected to Pd / Au electrodes for electrical transport testing. The HZO thickness is 2.3 nm. The overlapping region of the upper and lower FGT ferromagnetic layers in the vertical projection direction is the junction region, with an area of ​​approximately 150 μm. 2 The thickness of the upper electrode FGT ferromagnetic layer is 30 nm, and the thickness of the lower electrode FGT ferromagnetic layer is 60 nm. The preparation of this magnetic tunnel junction includes the following steps: 1. Preparation of the bottom electrode Using a Si substrate (SiO2 / Si) as the support substrate, a bottom electrode pattern was photolithographically patterned on the substrate using laser direct-write lithography with photoresist. Subsequently, a 5nm thick Pd layer and a 30nm thick Au layer were sequentially deposited using thermal evaporation. After evaporation, the sample was placed in acetone for a lift-off process to remove the photoresist, ultimately yielding a patterned Pd / Au bottom electrode (e.g., ...) on the SiO2 / Si substrate. Figure 3 (As shown).

[0066] 2. Mechanical peeling and transfer of the lower FGT layer Thin-layer FGT nanosheets were obtained by mechanically exfoliating bulk Fe3GeTe2 single crystals using PDMS. The FGT nanosheets on the PDMS were aligned with a pre-prepared Pd / Au bottom electrode, and the sample was slowly lowered to bring the FGT into contact with the bottom electrode. The sample was heated to 90°C and held for 10 minutes to release the FGT nanosheets and allow them to adhere firmly to the Pd / Au bottom electrode, forming the lower electrode FGT ferromagnetic layer (e.g., ...). Figure 3 (As shown).

[0067] 3. Preparation and transfer of self-supporting HZO ultrathin films 3.1 Growth of LSMO sacrificial layer and HZO thin film SrTiO3(100) single crystal was used as a substrate and ultrasonically cleaned with acetone and ethanol sequentially, then dried. Thin films were grown using a pulsed laser deposition system: first, a 23 nm thick LSMO sacrificial layer was deposited at 800 °C and an oxygen partial pressure of 100 mTorr; then, the temperature was raised in situ to 920 °C, and an HZO thin film was deposited at an oxygen partial pressure of 150 mTorr. The HZO thickness was precisely controlled to 2.3 nm by controlling the number of deposition pulses.

[0068] 3.2 Structural and Ferroelectric Characterization XRD and XRR tests were performed on the grown films to confirm the crystal structures of the LSMO and HZO films (see [link to XRD test]). Figure 4 ) and thickness (see Figure 5 ). Figure 4 The peaks of the STO(001) substrate and the epitaxially grown LSMO(100) can be seen near 23.24°, as well as the peaks of the STO(002) substrate and the epitaxially grown LSMO(002) near 46.48°. The typical HZO ferroelectric phase (111) appears near 30.4°. o The peaks of the phase indicate that the crystal structure of the bilayer film epitaxially grown on the STO(100) substrate is LSMO / HZO, and that HZO has a ferroelectric phase (111). o Mutually. Figure 5XRR data were analyzed using GlobalFit, yielding thicknesses of 23 nm and 2.3 nm for the LSMO / HZO bilayer film, respectively. To further verify the ferroelectricity of HZO, a 100 μm diameter circular Pd / Au top electrode was deposited on the sample surface, and PUND (Positive-Up-Negative-Down) tests were performed using LSMO as the bottom electrode. Clear ferroelectric hysteresis loops (such as...) were obtained. Figure 6 (as shown), maximum remanent polarization P r The value is approximately 8 μC / cm 2 This indicates that the grown HZO thin film has significant ferroelectricity.

[0069] 3.3 Release of self-supporting HZO PMMA was spin-coated onto the HZO thin film surface (4000 rpm / 1 min), and cured at 150 °C for 3 min. The sample was then immersed in a mixed solution of 1.4 mol / L HCl and 0.05 mol / L KI and etched at room temperature (25 °C) for approximately 12 h. After the LSMO layer was selectively dissolved, the film was slowly immersed in deionized water, and the PMMA / HZO bilayer film separated from the STO substrate and floated on the liquid surface (e.g., ...). Figure 7 (As shown).

[0070] 3.4 HZO transfer to the lower-level FGT The PMMA / HZO bilayer film in deionized water was transferred onto the target substrate, ensuring complete coverage of the lower electrode FGT ferromagnetic layer. The PMMA was then removed with acetone to obtain the well-transferred self-supported HZO (see [link to article]). Figure 8 ).

[0071] 4. Mechanical stripping and transfer of the upper FGT layer The bulk Fe3GeTe2 single crystal was mechanically exfoliated again using PDMS to obtain thin-layer FGT nanosheets. Using a transfer platform, the FGT nanosheets on the PDMS were aligned with the lower FGT layer, and the platform was slowly lowered to allow the upper and lower FGT layers to overlap and form a junction. The upper FGT layer was then released after heating at 90℃ for 10 min, forming an FGT / HZO / FGT sandwich structure with a junction area of ​​approximately 150 μm. 2 (like Figure 9 (As shown).

[0072] 5. Fabrication of the top electrode The top electrode pattern was created using laser direct writing exposure and development, ensuring it only contacts the upper FGT layer. Then, 5 nm Pd and 30 nm Au were sequentially deposited using thermal evaporation, followed by acetone lift-off to remove the photoresist, yielding the top electrode (e.g., ...). Figure 10(As shown). With this, the fabrication of the complete FGT / HZO / FGT magnetic tunnel junction device is complete.

[0073] 6. Device electrical transport testing The device was connected to a comprehensive physical property measurement system, and an out-of-plane magnetic field scan of ±5T was applied at 2K temperature, while the junction resistance was measured simultaneously. When the magnetic field scanned from positive to negative, the magnetization directions of the upper and lower FGT changed from parallel to antiparallel, and the resistance changed from a low-resistance state (R0). P ) jumps to a high-resistivity state (R) AP Repeat the above performance test twice. Calculate the tunneling magnetoresistance ratio TMR = (R AP -R P ) / R P ×100%, the measured TMR is approximately 140% (e.g. Figure 11 As shown in the figure, the excellent performance of the structure is verified.

[0074] Although preferred embodiments of the invention have been shown and described, it is conceivable that those skilled in the art can devise various modifications to the invention within the spirit and scope of the appended claims.

Claims

1. A magnetic tunnel junction, characterized in that, include: A lower electrode layer, a tunneling barrier layer, and an upper electrode layer; the tunneling barrier layer is disposed between the upper electrode layer and the lower electrode layer; The tunneling barrier layer includes a self-supporting hafnium zirconium oxide film; The thickness of the self-supporting hafnium zirconium oxide film is 1~3nm.

2. The magnetic tunnel junction according to claim 1, characterized in that, The overlapping region between the lower electrode layer and the upper electrode layer in the vertical projection direction is a junction region, and the area of ​​the junction region is 140~160μm. 2 .

3. The magnetic tunnel junction according to claim 1, characterized in that, The lower electrode layer and the upper electrode layer each independently comprise layered two-dimensional ferromagnetic material; The layered two-dimensional ferromagnetic material includes Fe3GeTe2; The thickness of the lower electrode layer and the upper electrode layer are each independently 3~100nm.

4. The magnetic tunnel junction according to claim 1, characterized in that, The hafnium zirconium oxide in the self-supporting hafnium zirconium oxide film is selected from Hf 0.5 Zr 0.5 O2.

5. A method for preparing a magnetic tunnel junction according to any one of claims 1 to 4, characterized in that, Includes the following steps: A perovskite conductive oxide sacrificial layer and a hafnium zirconium oxide layer are sequentially grown on a substrate by pulsed laser deposition. Polymethyl methacrylate was spin-coated onto the surface of the hafnium zirconium oxide and then subjected to heat treatment. The heat-treated sample was immersed in a mixed solution of HCl and KI to etch the perovskite conductive oxide sacrificial layer, resulting in a hafnium zirconium oxide film with a polymethyl methacrylate layer. A self-supported hafnium zirconium oxide film with a polymethyl methacrylate layer is transferred to the lower electrode layer, the polymethyl methacrylate layer is removed to form a self-supported hafnium zirconium oxide film on the lower electrode layer, and then an upper electrode layer is formed on the self-supported hafnium zirconium oxide film to obtain a magnetic tunnel junction.

6. The method for preparing a magnetic tunnel junction according to claim 5, characterized in that, The thickness of the perovskite conductive oxide sacrificial layer is 10~50 nm; The perovskite conductive oxide sacrificial layer includes La 0.67 Sr 0.33 MnO3.

7. The method for preparing a magnetic tunnel junction according to claim 5, characterized in that, The conditions for pulsed laser deposition growth of the perovskite conductive oxide sacrificial layer are: temperature 750~850℃, oxygen partial pressure 90~110 mTorr, and energy density 1~1.5 J / cm³. 2 ; The conditions for pulsed laser deposition growth of hafnium zirconium oxide are: temperature 900~950℃, oxygen partial pressure 140~160 mTorr, and energy density 1~1.5 J / cm³. 2 .

8. The method for preparing a magnetic tunnel junction according to claim 5, characterized in that, The temperature of the heat treatment is 120~150℃, and the time of the heat treatment is 3~5 minutes; In the mixed solution, the concentration of HCl is 0.5~1.5 mol / L and the concentration of KI is 0.002~0.05 mol / L; The etching temperature is 10~30℃, and the etching time is 6~24h.

9. The method for preparing a magnetic tunnel junction according to claim 6, characterized in that, The substrate includes a SrTiO3 single crystal substrate.

10. The application of the magnetic tunnel junction according to any one of claims 1 to 4 in a two-dimensional spin device research platform, a ferroelectric-spin coupled multi-state storage unit, an electrically controllable spin filter, or a magnetic sensor device.

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