Annealing process optimization and transport regulation and control method for antiferromagnetic Mn3Ge thin film

Abstract

The invention discloses an annealing process optimization and transport regulation and control method for an antiferromagnetic Mn3Ge thin film, and belongs to the technical field of information technology spintronics materials. A Mn3Ge thin film grows on a # imgabs0 # substrate, the grown Mn3Ge thin film is pure hexagonal opposite ferromagnetic, the crystal orientation is (0002) and # imgabs1 #, the Mn3Ge thin film successfully grows by using a single mixed target in which the ratio of Mn to Ge is 5: 1 through a magnetron sputtering method, a magnetron sputtering system heating module is further used for carrying out annealing treatment on the thin film, and the Mn3Ge thin film is prepared. The transport property of the material is regulated and controlled by controlling parameters such as the annealing temperature and the annealing time, so that the transport property of the antiferromagnetic material is further researched, and a spinning electronic device is subsequently prepared on the basis of the antiferromagnetic material.

Description

Technical Field

[0001] The invention relates to annealing process optimization and transport control technology of antiferromagnetic Mn3Ge thin film, belonging to the technical field of information technology spin electronics materials. Background Art

[0002] Entering the post-Moore era, spin electronics has flourished in basic research and applied research, becoming an important direction for the development of next-generation information technology. Scientists have made great progress in the field of spin electronics, but how to design ultra-small, ultra-high-speed, low-power spin electronics materials and devices that meet the needs of the future intelligent era still faces huge challenges. To develop high-performance spin electronics devices, it depends largely on the intrinsic properties of the material.

[0003] In recent years, antiferromagnetic materials have attracted extensive attention due to their advantages such as no stray fields, insensitivity to external magnetic fields, and ultrafast spin dynamics. For a long time, non-collinear antiferromagnetic materials were believed to have no anomalous Hall effect, and thus would not respond to external magnetic fields, making them undetectable and unsuitable for storage. Since the discovery of a large anomalous Hall effect at room temperature in Mn3Sn in 2015, the Mn3X (X = Sn, Ge, Ga, Ir, Pt) system has been in the research boom, mainly due to the excellent transport properties brought by the special lattice structure and electronic band structure of this material, which is expected to realize high-density, low-power spin electronics devices.

[0004] In 2014, J. Kubler et al. conducted theoretical calculations on the anomalous Hall conductivity of two specific antiferromagnetic materials, Mn3Sn and Mn3Ge, and found that their anomalous Hall conductivity can be as high as 250 (Ω·cm) -1 and 900(Ω·cm) -1 , which is comparable to traditional ferromagnetic materials. Theoretical calculations by B. Yan et al. show that Mn3Sn and Mn3Ge are topological Weyl metals (originally reported as semi-metals in the literature). Multiple Weyl points near the Fermi surface can contribute to Berry curvature, and the anomalous Hall effect in hexagonal opposite ferromagnets was predicted based on the calculation of band structure and Berry curvature. It was not until 2015 that S. Nakatsuji et al. experimentally studied the anomalous Hall effect in Mn3Sn and verified the theoretical prediction that "even without obvious magnetization, an anomalous Hall effect can be produced." It was subsequently proved that the anomalous Hall effect in Mn3Sn originated from the intrinsic mechanism, that is, the contribution of Berry curvature, and then the huge Hall effect in the same system was reported one after another.

[0005] Hexagonal ferromagnetic Mn3Ge has a hexagonal crystal structure (space group P63 / mmc) and is NBelow (about 400K), the Mn magnetic moment shows a non-collinear order of 120 degrees. The associated geometric frustration leads to a weak net magnetic moment. The hexagonal structural unit of Mn3Ge consists of two layers of triangularly arranged Mn atoms stacked along the c-axis. In each layer, the Mn atoms form a Kagome lattice, and Ge is located at the center of a hexagon. The hexagonal Mn3Ge film has a wealth of novel physical effects, such as the room temperature giant anomalous Hall effect (AHE), magneto-optical Kerr effect (MOKE), spin Hall effect (SHE) and possible topological Hall effect (THE). The study of the physical effects of the non-collinear antiferromagnetic Mn3Ge material provides a material for the development of a new generation of ultra-high-speed, high-stability and low-energy spin memory. It is expected that SOT devices based on Mn3Ge thin films with magnetic moment reversal can be developed without the need for an external magnetic field and current drive. At present, for storage devices based on this material system, Mn3Sn is relatively mature and has realized spin electronic devices that do not require an external field or have low power consumption. However, there are still major deficiencies in storage devices based on Mn3Ge. The challenge lies in the difficulty in growing hexagonal non-collinear antiferromagnetic Mn3Ge, such as the narrow growth temperature window, the precise ratio of the target material Mn and Ge, the adaptation of the substrate to the Mn3Ge lattice, and other factors. In addition, the grown Mn3Ge thin film has a small anomalous Hall resistance and a large reversal field, which makes it difficult to realize spin electronic devices that do not require an external field and have a low current reversal density. There is a lack of methods to regulate its transport properties, which is not conducive to the preparation and research of micro-nano devices.

[0006] The present invention is an improvement made to solve the above problems. Summary of the invention

[0007] The present invention provides an annealing process optimization and transport regulation technology for an antiferromagnetic Mn3Ge film. The present invention uses a magnetron sputtering heating system to change the annealing temperature, annealing time and other annealing process treatment of the hexagonal antiferromagnetic Mn3Ge film, optimizes the quality of the hexagonal Mn3Ge film, regulates its transport properties, and obtains a high-quality hexagonal Mn3Ge film with excellent transport properties, so as to realize a spin electronic device based on the Mn3Ge material.

[0008] To achieve the above purpose, the technical solution adopted by the present invention is:

[0009] An antiferromagnetic Mn3Ge film is characterized in that it has a pure hexagonal phase lattice structure and a non-collinear antiferromagnetic spin orientation.

[0010] The antiferromagnetic Mn3Ge film is deposited on a On the substrate, the lattice orientation is (0002) and

[0011] An annealing process optimization and transport control method for an antiferromagnetic Mn3Ge thin film, characterized in that it comprises the following steps:

[0012] The first step is to prepare a pure hexagonal Mn3Ge thin film by epitaxially growing a pure hexagonal Mn3Ge thin film on an Al2O3 substrate using an ultra-high vacuum magnetron sputtering system and a single mixed target with a Mn and Ge composition ratio of 5:1. First, the Al2O3 substrate sent into the coating chamber is heated and kept at 400°C for 20 minutes, and then sputtered in a high vacuum environment at 400°C to obtain a pure hexagonal Mn3Ge thin film.

[0013] In the second step, the hexagonal Mn3Ge film is annealed at a temperature of 600°C for 4 hours.

[0014] Preferably, in order to obtain a more excellent antiferromagnetic Mn3Ge film, the process steps are further optimized as follows:

[0015] The preparation of pure hexagonal Mn3Ge thin film in the first step above, the specific experimental steps are as follows:

[0016] (1) Place the cleaned substrate into the card slot of the sample holder, and place the sample holder into the sample library;

[0017] (2) Click the vacuum start button on the sample library to start vacuuming. Wait until the vacuum degree reaches 4×10 -4 After Pa, the sample tray is transported to the sample station in the coating room;

[0018] (3) Setting the sputtering parameters for growing pure hexagonal Mn3Ge thin films;

[0019] (4) Wait for the vacuum degree of the coating chamber to reach 6×10 -7 After Pa, the sputtering growth can be started automatically;

[0020] (5) After the sputtering is completed, click the "Stop Sputtering" button, and wait for the coating chamber temperature to naturally cool down to room temperature to complete the sputtering growth of the Mn3Ge film;

[0021] (6) Adjust the sample lifting motor and the rotation motor to the handover position for sampling, and take the sample tray to the sample library;

[0022] (7) Click the vacuum button of the sample library to close, and wait until the front stage valve 1 is closed to remove the sample holder to obtain the pure hexagonal phase Mn3Ge film;

[0023] The substrate used in step (1) is 1*1 cm The lattice orientation of Al2O3 is

[0024] The sputtering parameters in step (3) are as follows: the sputtering gas is argon; the heating and holding temperature curve is specifically a curve step number of 2 steps, the target temperature 1 is 400°C, the heating time is 26min; the target temperature 2 is 400°C, and the holding time is 20min; the sample stage rotation rate is 5rpm; the DC power supply power is 50W; the pre-sputtering pressure 1 is 1.5Pa, and the sputtering time is 30S; the pre-sputtering pressure 2 is 0.6Pa, and the sputtering time is 30S; the formal sputtering pressure is 0.6Pa, and the sputtering time is 400S;

[0025] The annealing method for the hexagonal Mn3Ge film in the second step includes the following steps:

[0026] The grown pure hexagonal Mn3Ge film is annealed using a magnetron sputtering heating system to obtain a high-quality hexagonal Mn3Ge film with excellent transport properties; the specific steps are as follows:

[0027] (1) Place the grown hexagonal Mn3Ge film into the sample holder slot, with the side of the hexagonal Mn3Ge film facing upward, and then place the sample holder into the sample library;

[0028] (2) Click the vacuum start button on the sample library to start vacuuming. Wait until the vacuum degree reaches 4×10 -4 After Pa, the sample tray is transported to the sample station in the coating room;

[0029] (3) Setting the annealing temperature curve;

[0030] (4) The vacuum degree of the coating chamber reaches 6×10 -6 Pa, turn on the sample rotation motor;

[0031] (5) Click to start the annealing temperature curve;

[0032] (6) Heating to 600°C, keeping the temperature for 4 hours, and then naturally cooling to room temperature to complete annealing;

[0033] (7) Turn off the sample rotation motor;

[0034] (8) Adjust the sample lifting motor and the rotation motor to the handover position for sampling, and take the sample holder to the sample library (9) Click the vacuum button of the sample library to close it, and wait until the front stage valve 1 is closed to take out the sample holder to obtain the annealed pure hexagonal phase Mn3Ge film;

[0035] It is further preferred that the annealing temperature curve in step (3) has 2 steps, target temperature 1 is 600° C., heating time is 39 min, target temperature 2 is 600° C., and heat preservation time is 4 h;

[0036] It is further preferred that the speed of the sample rotation motor in step (4) is 5 rpm;

[0037] The present invention proposes the optimization and regulation of the transport properties of the hexagonal antiferromagnetic Mn3Ge film, which is beneficial to the development of spin electronic devices of antiferromagnetic materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is a diagram showing the X-ray diffraction measurement results of the pure hexagonal phase Mn3Ge film of the present invention.

[0039] Figure 2 This is a selected area electron diffraction image of the Mn3Ge thin film according to Example 1 of the present invention.

[0040] Figure 3 This is the anomalous Hall effect diagram of the hexagonal opposite ferromagnetic Mn3Ge film in Example 1 of the present invention.

[0041] Figure 4 This is the anomalous Hall effect diagram of the hexagonal opposite ferromagnetic Mn3Ge film in Example 2 of the present invention.

[0042] Figure 5 This is the anomalous Hall effect diagram of the hexagonal opposite ferromagnetic Mn3Ge film in Example 3 of the present invention. DETAILED DESCRIPTION

[0043] In order to make the technical solution, implementation details and final effect of the present invention easy to understand, the technical solution in the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiment of the present invention. Obviously, the described embodiment is only a part of the embodiment of the present invention, not all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0044] Embodiment 1: A method for preparing a pure hexagonal Mn3Ge thin film, comprising the following steps:

[0045] (1) Place the cleaned substrate into the card slot of the sample holder, and place the sample holder into the sample library;

[0046] (2) Click the vacuum start button on the sample library to start vacuuming. Wait until the vacuum degree reaches 4×10 -4 After Pa, the sample tray is transported to the sample station in the coating room;

[0047] (3) Setting the sputtering parameters for growing pure hexagonal Mn3Ge thin films (including: heating and holding temperature curve, specifically, the curve steps are 2 steps, the target temperature 1 is 400°C, and the heating time is 26 min;

[0048] Target temperature 2 is 400°C, and the temperature is kept for 20 minutes;

[0049] The sample stage rotation speed is 5 rpm;

[0050] DC power supply power 50W;

[0051] The pre-sputtering gas pressure 1 is 1.5 Pa, and the sputtering time is 30 s;

[0052] The pre-sputtering gas pressure 2 is 0.6 Pa, and the sputtering time is 30 s;

[0053] The formal sputtering pressure is 0.6Pa, and the sputtering time is 400S;);

[0054] (4) Wait for the vacuum degree of the coating chamber to reach 6×10 -7 After Pa, the sputtering growth can be started automatically;

[0055] (5) After the sputtering is completed, click the "Stop Sputtering" button, and wait for the coating chamber temperature to naturally cool down to room temperature to complete the sputtering growth of the Mn3Ge film;

[0056] (6) Adjust the sample lifting motor and the rotation motor to the handover position for sampling, and take the sample tray to the sample library;

[0057] (7) Click the vacuum button of the sample library to close, and wait until the front stage valve 1 is closed to remove the sample holder to obtain the pure hexagonal phase Mn3Ge film;

[0058] Embodiment 2: Annealing treatment of hexagonal opposite ferromagnetic Mn3Ge film comprises the following steps:

[0059] (1) Place the hexagonal Mn3Ge film grown in Example 1 into the sample holder slot, with the side of the hexagonal Mn3Ge film facing upward, and then place the sample holder in the sample library;

[0060] (2) Click the vacuum start button on the sample library to start vacuuming. Wait until the vacuum degree reaches 4×10 -4 After Pa, the sample tray is transported to the sample station in the coating room;

[0061] (3) Set the annealing temperature curve with 2 steps, target temperature 1 is 600°C, heating time is 39 min; target temperature 2 is 600°C, holding time is 4 h;

[0062] (4) Set the sample rotation motor speed to 5 rpm and the vacuum degree of the coating chamber to 6 × 10 -6 Pa, turn on the sample rotation motor;

[0063] (5) Click to start the annealing temperature curve;

[0064] (6) Heating to 600°C, keeping the temperature for 4 hours, and then naturally cooling to room temperature to complete annealing;

[0065] (7) Click to turn off the sample rotation motor;

[0066] (8) Adjust the sample lifting motor and the rotation motor to the handover position for sampling, and take the sample tray to the sample library;

[0067] (9) Click the vacuum button of the sample library to close, and wait until the front stage valve 1 is closed to remove the sample holder to obtain the pure hexagonal phase Mn3Ge film;

[0068] Embodiment 3: Annealing treatment of hexagonal opposite ferromagnetic Mn3Ge film comprises the following steps:

[0069] (1) Place the hexagonal Mn3Ge film grown in Example 1 into the sample holder slot, with the side of the hexagonal Mn3Ge film facing upward, and then place the sample holder in the sample library;

[0070] (2) Click the vacuum start button on the sample library to start vacuuming. Wait until the vacuum degree reaches 4×10 -4 After Pa, the sample tray is transported to the sample station in the coating room;

[0071] (3) Set the annealing temperature curve with 2 steps, target temperature 1 is 650°C, heating time is 43 min; target temperature 2 is 650°C, holding time is 2 h;

[0072] (4) Set the sample rotation motor speed to 5 rpm and turn on the sample rotation motor;

[0073] (5) Click to start the annealing temperature curve;

[0074] (6) Heating to 650°C, keeping the temperature for 2 hours, and then naturally cooling to room temperature to complete annealing;

[0075] (7) Click to turn off the sample rotation motor;

[0076] (8) Adjust the sample lifting motor and the rotation motor to the handover position for sampling, and take the sample holder to the sample library; (9) Click the vacuum button of the sample library to close, and wait until the front valve 1 is closed to remove the sample holder to obtain the annealed pure hexagonal phase Mn3Ge film.

[0077] The hexagonal Mn3Ge thin films obtained in Examples 1-3 of the present invention were analyzed as follows:

[0078] Figure 1 This is the XRD diffraction pattern of the Mn3Ge film of Example 1. It can be seen that the grown film is a pure hexagonal phase Mn3Ge film; Figure 2 The electron diffraction pattern further confirmed its hexagonal structure. Figure 3 The anomalous Hall test results show that it has good transport properties, but its perpendicular magnetic anisotropy needs to be improved; by annealing the film at 600℃ for 4h, Figure 4As shown in the figure, the Hall jump is increased and the perpendicular magnetic anisotropy is improved. Then, a higher annealing temperature is used to anneal the film at 650℃ for 2h. Its transport properties are shown in the figure. Figure 5 As shown in Figure 2, the reversal field is greatly reduced and the perpendicular magnetic anisotropy is significantly enhanced. This provides favorable conditions for realizing spin electronic devices based on antiferromagnetic Mn3Ge films without external fields and low current reversal density.

Claims

1. An antiferromagnetic Mn3Ge film, characterized in that: It has a pure hexagonal lattice structure and non-collinear antiferromagnetic spin orientation.

2. An antiferromagnetic Mn3Ge film according to claim 1, characterized in that: The antiferromagnetic Mn3Ge thin film is deposited on an Al2O3 (1102) substrate using a magnetron sputtering system, and has lattice orientations of (0002) and (2021).

3. The method for optimizing the annealing process and regulating the transport of an antiferromagnetic Mn3Ge thin film according to claim 1 or 2, characterized in that: The following steps are involved: The first step is to prepare a pure hexagonal Mn3Ge thin film by epitaxially growing a pure hexagonal Mn3Ge thin film on an Al2O3 substrate using an ultra-high vacuum magnetron sputtering system and a single mixed target with a Mn and Ge composition ratio of 5:

1. The Al2O3 substrate sent into the coating chamber is first heated and kept at 400°C for 20 minutes, and then sputtered in a high vacuum environment at 400°C to obtain a pure hexagonal Mn3Ge thin film. In the second step, the hexagonal Mn3Ge film is annealed at a temperature of 600°C for 4 hours.

4. The method according to claim 3, characterized in that In the first step, the preparation of pure hexagonal Mn3Ge thin film, the specific experimental steps are as follows: (1) Place the cleaned substrate into the card slot of the sample holder, and place the sample holder into the sample library; (2) Click the vacuum start button on the sample library to start vacuuming. Wait until the vacuum degree reaches 4×10 -4 After Pa, the sample tray is transported to the sample station in the coating room; (3) Setting the sputtering parameters for growing pure hexagonal Mn3Ge thin films; (4) Wait for the vacuum degree of the coating chamber to reach 6×10 -7 After Pa, the sputtering growth can be started automatically; (5) After the sputtering is completed, click the "Stop Sputtering" button, and wait for the coating chamber temperature to naturally cool down to room temperature to complete the sputtering growth of the Mn3Ge film; (6) Adjust the sample lifting motor and the rotation motor to the handover position for sampling, and take the sample tray to the sample library; (7) Click the vacuum button of the sample library to close it. Wait until the front valve 1 is closed and then take out the sample holder to obtain the pure hexagonal Mn3Ge film.

5. The method according to claim 3, characterized in that The substrate used in step (1) is 1*1cm—— Al2O3(1102); the lattice orientation of the Al2O3 is (1102).

6. The method according to claim 3, characterized in that The sputtering parameters described in step (3) are as follows: the sputtering gas is argon; the heating and insulation temperature curve, specifically, the curve step number is 2 steps, the target temperature 1 is 400°C, the heating time is 26min; the target temperature 2 is 400°C, and the insulation time is 20min; the sample stage rotation rate is 5rpm; the DC power supply power is 50W; the pre-sputtering pressure 1 is 1.5Pa, and the sputtering time is 30S; the pre-sputtering pressure 2 is 0.6Pa, and the sputtering time is 30S; the formal sputtering pressure is 0.6Pa, and the sputtering time is 400S.

7. The method according to claim 3, characterized in that The annealing method for the hexagonal Mn3Ge film in the second step comprises the following steps: (1) Place the grown hexagonal Mn3Ge film into the sample holder slot, with the side of the hexagonal Mn3Ge film facing upward, and then place the sample holder into the sample library; (2) Click the vacuum start button on the sample library to start vacuuming. Wait until the vacuum degree reaches 4×10 -4 After Pa, the sample tray is transported to the sample station in the coating room; (3) Setting the annealing temperature curve; (4) The vacuum degree of the coating chamber reaches 6×10 -6 Pa, turn on the sample rotation motor; (5) Click to start the annealing temperature curve; (6) Heating to 600°C, keeping the temperature for 4 hours, and then naturally cooling to room temperature to complete annealing; (7) Turn off the sample rotation motor; (8) Adjust the sample lifting motor and the rotation motor to the handover position for sampling, and take the sample holder to the sample library (9) Click the sample library vacuum one-button to close, and wait until the front stage valve 1 is closed to remove the sample holder to obtain the annealed pure hexagonal phase Mn3Ge film.

8. The method according to claim 7, characterized in that The annealing temperature curve in step (3) has 2 steps, target temperature 1 is 600° C., heating time is 39 min, target temperature 2 is 600° C., and insulation time is 4 h.

9. The method according to claim 3, characterized in that Step (4) The sample rotation motor speed is 5 rpm.

10. Use of the antiferromagnetic Mn3Ge film according to claim 1 or 2 in spintronic devices.

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