Magnetic Van der Waals film and preparation method and application thereof

Abstract

The invention discloses a magnetic Van der Waals film and a preparation method and application thereof, and particularly relates to the field of device preparation. Comprising the following steps: setting growth conditions, and sequentially epitaxially growing a preset number of layers of magnetic Van der Waals films on the surface of a substrate; wherein after each layer of magnetic Van der Waals film is obtained, in-situ RHEED, structure and intrinsic magnetism measurement is carried out on the magnetic Van der Waals film, and the mass of the magnetic Van der Waals film of the current layer is determined according to the measurement result; and when the quality reaches a preset condition, epitaxially growing a next layer of magnetic Van der Waals film. And preparing the magnetic Van der Waals film into a magnetic head exchange bias device by adopting a micro-nano etching technology, and carrying out transport measurement on the magnetic head exchange bias device. Based on the method, the magnetic Van der Waals film is used for preparing the magnetic head exchange bias device, and the thickness, the scale and the cleanliness of the interface of the magnetic head exchange bias device can be accurately controlled.

Description

Technical Field

[0001] The present application relates to the field of device preparation, and in particular to a magnetic van der Waals film and its preparation method and application. Background Art

[0002] Exchange-biased antiferromagnetic / ferromagnetic (AF / FM) systems are key components in spintronic devices such as giant magnetoresistance / tunnel magnetoresistance (GMR / TMR) read heads, primarily used for magnetic storage. AF / FM systems used in commercial magnetic heads are typically fabricated from bilayers of conventional metal alloys such as IrMn / NiFe. In 2020, the applicant and his team demonstrated for the first time the exchange bias phenomenon in a mechanically exfoliated van der Waals heterojunction, CrCl₃ / Fe₃GeTe₂, achieving a large exchange bias field exceeding 50 mT at 2.5 K. This value is comparable to or even higher than that of conventional exchange-biased bilayers. More importantly, the magnitude of this exchange bias field can be tuned by varying the thickness of the CrCl₃ and the cooling field. Since then, numerous research groups both domestically and internationally have demonstrated exchange bias effects in van der Waals AF / FM heterojunctions. The advantages of using exchange-biased devices based on van der Waals magnets include mechanical flexibility and the potential for device size reduction toward atomic-scale thicknesses.

[0003] Since current van der Waals devices are mostly prepared using mechanical exfoliation and transfer methods, the exchange bias devices based on van der Waals materials currently have the following main defects: the thickness cannot be precisely controlled. Summary of the Invention

[0004] The main purpose of this application is to provide a magnetic van der Waals film and its preparation method and application, aiming to solve the problem that the thickness of existing van der Waals devices cannot be accurately controlled.

[0005] To achieve the above-mentioned objectives, the present application provides a method for preparing a magnetic van der Waals film, comprising: setting growth conditions, and sequentially epitaxially growing a preset number of layers of magnetic van der Waals films on the surface of a substrate; wherein, after each layer of magnetic van der Waals film is obtained, in-situ RHEED, structure, and intrinsic magnetic measurements are performed on it, and the quality of the magnetic van der Waals film of the current layer is determined based on the measurement results; when the quality reaches the preset conditions, the next layer of magnetic van der Waals film is epitaxially grown.

[0006] Optionally, the method further includes adjusting growth conditions and re-performing epitaxial growth when the quality does not meet the preset conditions until the quality meets the preset conditions.

[0007] Optionally, the method for measuring intrinsic magnetism includes: transferring the magnetic van der Waals film to a vacuum measurement chamber by vacuum transmission, performing structural and intrinsic magnetic measurements to obtain intrinsic magnetic parameters; after the measurement, vacuum transmitting the magnetic van der Waals film to the original growth environment.

[0008] Optionally, the epitaxial growth is performed in an MBE preparation chamber.

[0009] Optionally, parameters measured by in-situ RHEED include flatness, surface atomic structure, and lattice constant.

[0010] Optionally, the measurement parameters of intrinsic magnetism include atomic arrangement, electronic state density and microscopic magnetic moment.

[0011] To achieve the above-mentioned purpose, the present application also provides a magnetic van der Waals film, which is obtained by a method for preparing a magnetic van der Waals film.

[0012] To achieve the above objectives, the present application also provides an application of a magnetic van der Waals film in a magnetic head exchange bias device.

[0013] Optionally, the magnetic van der Waals film is prepared into a magnetic head exchange bias device by using micro-nano etching technology, and transport measurement is performed on the magnetic head exchange bias device.

[0014] Optionally, transport measurements include anomalous Hall effect and magnetoresistance measurements.

[0015] Compared with the prior art, the present invention has the following advantages: The method for preparing the magnetic van der Waals film of the present invention accurately controls the thickness of the film through the van der Waals epitaxy method and can effectively expand the lateral size of the film; accurately characterizes the film properties through the matching in-situ measurement technology method, and further adjusts the van der Waals epitaxy conditions through the obtained parameter feedback, thereby achieving precise control of the film size and quality.

[0016] The application of the magnetic van der Waals film of the present invention, in preparing a magnetic head exchange bias device using the magnetic van der Waals film, can precisely control the thickness of the magnetic head exchange bias device, thereby achieving the purpose of precisely controlling the magnitude of the exchange bias field; and can ensure large-scale and high-yield preparation of the device. By accurately characterizing the film properties, it is possible to achieve precise control of the dimensions and quality of the magnetic head exchange bias device. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A schematic flow chart of a method for preparing a magnetic van der Waals film according to the present application; Figure 2 This is a graph showing the test results of the VSe2 thin film obtained in Example 1.

[0018] The realization of the objectives, functional features and advantages of this application will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0019] To make the objectives, technical solutions, and advantages of this application more clear, the technical solutions of this application will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the embodiments described are only part of the embodiments of this application, not all of them. Based on the embodiments of this application, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of this application.

[0020] The first embodiment of the present invention provides a method for preparing a magnetic van der Waals film, such as Figure 1 The specific steps are as follows: Growth conditions are set, and a predetermined number of layers of magnetic van der Waals thin films are sequentially epitaxially grown on the substrate surface. After each layer of magnetic van der Waals thin film is obtained, in-situ RHEED, structural, and intrinsic magnetic measurements are performed on it, and the quality of the magnetic van der Waals thin film of the current layer is determined based on the measurement results. When the quality meets the predetermined conditions, the next layer of magnetic van der Waals thin film is epitaxially grown. If the quality does not meet the predetermined conditions, the growth conditions are adjusted and epitaxial growth is repeated until the quality meets the predetermined conditions. The growth conditions include a combination of one or more of growth rate, growth temperature, and growth pressure.

[0021] Specifically, the intrinsic magnetic measurement method includes: transferring the magnetic van der Waals film to a vacuum measurement chamber via vacuum transport, performing structural and intrinsic magnetic measurements to obtain intrinsic magnetic parameters; after the measurements, vacuum transporting the magnetic van der Waals film back to its original growth environment. Intrinsic magnetic measurements include X-ray absorption measurements or X-ray magnetic circular dichroism (XAS / XMCD) measurements, and the measured parameters include atomic arrangement, electronic density of states, and microscopic magnetic moment.

[0022] Epitaxial growth is performed in an MBE preparation chamber, which serves as the original growth environment. In-situ RHEED measurements measure parameters such as flatness, surface atomic structure, and lattice constant.

[0023] A second embodiment of the present invention provides a magnetic van der Waals thin film obtained by a method for preparing a magnetic van der Waals thin film based on epitaxial growth.

[0024] A third embodiment of the present invention provides an application of a magnetic van der Waals film in a magnetic head exchange bias device. Specifically, the application method comprises fabricating the magnetic van der Waals film into a magnetic head exchange bias device using micro-nanolithography technology, and performing transport measurements on the magnetic head exchange bias device. The transport measurements include anomalous Hall effect (AHE) and magnetoresistance (MR) measurements.

[0025] In this embodiment, the thickness of the thin film and the magnetic head exchange bias device is precisely controlled by the van der Waals epitaxy method, thereby achieving the purpose of precisely controlling the size of the exchange bias field; at the same time, the lateral size of the material is effectively expanded to ensure large-scale and high-yield preparation of the device; through the use of supporting in-situ measurement technology, the material properties are accurately characterized, and the conditions of the van der Waals epitaxy are further adjusted through the obtained parameter feedback, thereby achieving precise control of the size and quality of each dimension of the device.

[0026] Example 1 Preparation of two-dimensional van der Waals material VSe2 Step S1, placing the substrate in an MBE preparation chamber, and epitaxially growing a first layer of VSe2 thin film on the surface of the substrate; Step S2, performing in-situ RHEED measurement on the VSe2 film obtained in step S1 in an MBE preparation chamber to obtain the lattice arrangement and lattice constant of the film; Step S3, by vacuum transport, the VSe2 film obtained in step S1 is transferred to a vacuum measurement chamber, and STM and XAS / XMCD measurements are performed, respectively. Figure 2 As shown in (a), the STM image shows that the height of the single-layer VSe2 film is about 7Å, which is consistent with the theoretical calculation; Figure 2 As shown in (b), XMCD measurement is performed on a single-layer VSe2 film, the magnetic field is parallel to the film surface, and the X-ray incident angle is 45 degrees; XAS has two typical VSe2 absorption peaks, such as Figure 2 As indicated by the arrow in (c), the quality of the first VSe2 film meets the requirements, and the next step is performed. If the film quality does not meet the requirements at this time, the process returns to step S1, adjusts the growth conditions, and continues epitaxial growth on the VSe2 film obtained in step S1 until the film quality meets the requirements, and the next step is performed. In step S4, the first layer of VSe2 film is formed on the surface. Return to step S1 and place the VSe2 film in the MBE preparation chamber to grow and optimize the second layer of magnetic van der Waals film. At this time, the interface between the first and second layers of film is formed to obtain the final VSe2 film, namely the AF / FM film.

[0027] Step S5: Using micro-nano etching technology to prepare a magnetic head exchange bias device on the VSe2 thin film, and performing AHE and MR measurements on it.

[0028] The above are only preferred embodiments of the present application and do not limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A method for preparing a magnetic van der Waals film, characterized in that: include: Setting growth conditions to sequentially epitaxially grow a preset number of magnetic van der Waals thin films on the substrate surface; After each layer of magnetic van der Waals film is obtained, in-situ RHEED, structure and intrinsic magnetic measurements are performed on it, and the quality of the magnetic van der Waals film of the current layer is determined based on the measurement results; When the quality reaches a preset condition, a next layer of magnetic van der Waals film is epitaxially grown.

2. The method for preparing a magnetic van der Waals film according to claim 1, wherein: Also includes, When the quality does not meet the preset conditions, the growth conditions are adjusted and the epitaxial growth is performed again until the quality meets the preset conditions.

3. The method for preparing a magnetic van der Waals film according to claim 1, wherein: The method for measuring the intrinsic magnetism includes: The magnetic van der Waals film is transferred to a vacuum measurement chamber by vacuum transfer, and structural and intrinsic magnetic measurements are performed to obtain intrinsic magnetic parameters. After the measurement is completed, the magnetic van der Waals film is vacuum-transferred to the original growth environment.

4. The method for preparing a magnetic van der Waals film according to claim 1, wherein: The epitaxial growth is carried out in an MBE preparation chamber.

5. The method for preparing a magnetic van der Waals film according to claim 1, wherein: The parameters measured by the in-situ RHEED include flatness, surface atomic structure, and lattice constant.

6. The method for preparing a magnetic van der Waals film according to claim 1, wherein: The measurement parameters of the intrinsic magnetism include atomic arrangement, electronic state density and microscopic magnetic moment.

7. A magnetic van der Waals film, characterized in that The method for preparing an epitaxial magnetic van der Waals film is used to prepare the film.

8. Use of the magnetic van der Waals film according to claim 7 in a magnetic head exchange bias device.

9. The use of the magnetic van der Waals film in a magnetic head exchange bias device according to claim 8, characterized in that: The magnetic van der Waals film is prepared into a magnetic head exchange bias device by adopting micro-nano etching technology, and transport measurement is performed on the magnetic head exchange bias device.

10. Use of the magnetic van der Waals film in a magnetic head exchange bias device according to claim 9, characterized in that: The transport measurements include anomalous Hall effect and magnetoresistance measurements.

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