A two-dimensional van der waals homostructure with adjustable exchange bias size and a preparation method thereof

Abstract

This invention discloses a two-dimensional van der Waals homogeneous structure with adjustable exchange bias, relating to the field of magnetic storage technology. The invention comprises a two-dimensional van der Waals ferromagnetic layer and a two-dimensional van der Waals antiferromagnetic layer stacked on top of each other. The thickness of both the ferromagnetic and antiferromagnetic layers is 2-200 nm, and the thickness ratio of the ferromagnetic and antiferromagnetic layers is x:(1-x), where x ranges from 0.1 to 0.9. The beneficial effect of this invention is that existing exchange bias methods are difficult to control in terms of bias magnitude. Even when an exchange bias can be induced, the magnitude of the exchange bias field cannot be controlled. This invention achieves and controls the exchange bias magnitude by adjusting the relative proportion of the thicknesses of the ferromagnetic and antiferromagnetic layers. The higher the proportion of the antiferromagnetic layer, the larger the exchange bias field.

Description

Technical Field

[0001] This invention relates to the field of magnetic storage technology, specifically to a two-dimensional van der Waals homogeneous structure with adjustable exchange bias and its preparation method. Background Technology

[0002] Magnetic storage is one of the most important technologies in the modern electronics industry. The recording and retrieval of high-density information relies heavily on magnetic storage technology; for example, hard drives in electronic products such as computers and mobile phones use magnetic storage. To ensure the stability and reliability of the read / write operation of the magnetic head, the magnetic state of the ferromagnetic material in the head needs to be stabilized. Current technology uses an antiferromagnetic material to pin the ferromagnetic material, thus stabilizing its magnetic state. The basic principle of this technology is the exchange bias effect.

[0003] Exchange bias effect: When an antiferromagnetic material (commonly NiO or CoO thin film) and a ferromagnetic material (commonly NiFe or Co thin film) form a magnetic heterojunction, the antiferromagnetic material will pin the magnetism of the ferromagnetic material, causing the hysteresis loop of the ferromagnetic material to deviate from zero. This is the exchange bias effect. Figure 1 As shown.

[0004] To meet the demand for more powerful and portable electronic products, the electronics industry needs to move towards wearable, low-power, and miniaturized designs. The key to realizing the exchange bias effect is constructing an "antiferromagnetic-ferromagnetic" magnetic structure. Current traditional technologies are mainly based on magnetic thin films grown on substrates, which lack flexibility, thinness, and light transmittance, failing to meet the future development direction of low-dimensional magnetic devices. Furthermore, the exchange bias field (the magnitude of the hysteresis loop's deviation from zero, generally denoted by H) based on traditional thin film systems... EB (This indicates that) the stability of magnetic recording devices depends primarily on the material itself. Once the antiferromagnetic and ferromagnetic materials are determined, the exchange bias field is also determined, making it difficult to adjust according to actual conditions. Moreover, since traditional antiferromagnetic materials form multiple easy magnetization axes or multiple antiferromagnetic domains, as the number of cyclic field applications increases, the antiferromagnets will relax, causing the bias effect to gradually decrease, i.e., the training effect of exchange bias. The existence of this effect will greatly affect the stability of magnetic recording devices.

[0005] Van der Waals magnetic materials, due to their layered structure and strong magnetic anisotropy, can maintain their magnetism in thin layers without the need for a substrate, thus well meeting the needs of future low-dimensional magnetic devices. Van der Waals magnetic materials can be divided into two main categories: ferromagnetic materials and antiferromagnetic materials. Ferromagnetic materials mainly include: transition metal halides (CrI3, CrBr3, VI3), transition metal tellurides (CrSiTe3, CrGeTe3, Fe3GeTe2, Fe4GeTe2, Fe5GeTe2), etc.; antiferromagnetic materials mainly include: transition metal phosphine chalcogenides (FePS3, MnPS3, NiPS3, CoPS3, FePSe3, MnPSe3, CrPS4), transition metal halides (CrCl3), etc. The magnetism of two-dimensional van der Waals magnetic materials is easily modulated by external means. The same material can exhibit both ferromagnetism and antiferromagnetism, and most of them have strong out-of-plane anisotropy. In thin layers, their magnetic domains are generally large.

[0006] The English literature Zheng G, WQ Xie, Albarakati S, et al. Gate-Tuned Interlayer Coupling in van der Waals Ferromagnet Fe3GeTe2 Nanoflakes[J]. 2020. describes the construction of Fe3GeTe2:H- / Fe3GeTe2 heterojunctions through proton intercalation, thereby inducing the appearance of exchange bias. The exchange bias can be induced by adjusting the voltage, but no exchange bias will appear when the voltage is negative, and exchange bias will appear when the positive voltage reaches 4.4. The magnitude of the bias is random and the size of the exchange bias field cannot be precisely controlled by changing the voltage. Summary of the Invention

[0007] The technical problem to be solved by the present invention is that although the prior art has achieved the exchange bias phenomenon in two-dimensional van der Waals magnetic materials through proton intercalation, the magnitude of the bias is random and has a training effect, and the magnitude of the exchange bias field cannot be controlled. The present invention provides a two-dimensional van der Waals homogeneous structure with adjustable exchange bias and its preparation method.

[0008] The present invention solves the above-mentioned technical problems through the following technical means:

[0009] A two-dimensional van der Waals homogeneous structure with adjustable exchange bias includes two-dimensional van der Waals ferromagnetic layers and two-dimensional van der Waals antiferromagnetic layers stacked on top of each other. The thickness of the ferromagnetic layer and the antiferromagnetic layer is 2-200 nm, and the thickness ratio of the ferromagnetic layer to the antiferromagnetic layer is x:(1-x), where x ranges from 0.1 to 0.9.

[0010] Beneficial effects: Existing exchange bias methods are difficult to control in terms of bias magnitude. Even when it is known that an exchange bias can be induced, the magnitude of the exchange bias field cannot be controlled. This invention achieves and controls the magnitude of the exchange bias by adjusting the relative proportion of the thickness of the ferromagnetic layer and the antiferromagnetic layer. The higher the proportion of the antiferromagnetic layer, the larger the exchange bias field.

[0011] The preparation method of the above-mentioned two-dimensional van der Waals homostructure with adjustable exchange bias includes the following steps: stacking a two-dimensional van der Waals ferromagnetic layer with a thickness of 2-200 nm and a two-dimensional van der Waals antiferromagnetic layer with a thickness of 2-200 nm, adjusting the thickness ratio of the ferromagnetic layer to the antiferromagnetic layer to x:(1-x), where x ranges from 0.1 to 0.9, to obtain a two-dimensional van der Waals homostructure with adjustable exchange bias.

[0012] Beneficial effects: Existing exchange bias methods are difficult to control in terms of bias magnitude. Even when it is known that an exchange bias can be induced, the magnitude of the exchange bias field cannot be controlled. This invention achieves and controls the magnitude of the exchange bias by adjusting the relative proportion of the thickness of the ferromagnetic layer and the antiferromagnetic layer. The higher the proportion of the antiferromagnetic layer, the larger the exchange bias field.

[0013] The method for preparing the above-mentioned two-dimensional van der Waals homostructure with adjustable exchange bias includes the following steps:

[0014] (1) Place a two-dimensional van der Waals magnetic sheet with a thickness of 2-200 nm on a first carrier, attach an organic film to a second carrier, and set the organic film toward the two-dimensional van der Waals magnetic sheet.

[0015] (2) Apply uniaxial pressure of different magnitudes perpendicular to the surface of the two-dimensional van der Waals magnetic sheet to the organic thin film. The uniaxial pressure is 0.1-1 GPa. Maintain this pressure for a period of time to form a two-dimensional van der Waals ferromagnetic layer and a two-dimensional van der Waals antiferromagnetic layer that are superimposed in a certain proportion. The thickness ratio of the ferromagnetic layer to the antiferromagnetic layer is x:(1-x), where x ranges from 0.1 to 0.9.

[0016] Beneficial effects: This invention uses a single two-dimensional magnetic material and applies uniaxial pressure perpendicular to the sample surface to induce the simultaneous formation of an antiferromagnetic layer and a ferromagnetic layer. While an exchange bias occurs, the magnitude of the exchange bias field can be controlled by setting different magnitudes of uniaxial pressure within a certain range. When the uniaxial pressure increases from 0.1 to 1 GPa, the magnitude of the exchange bias field increases sequentially.

[0017] When the uniaxial pressure is less than 0.1 GPa, an exchange bias cannot be induced, and the exchange bias cannot be controlled.

[0018] When the uniaxial pressure is greater than 1 GPa, according to theoretical predictions, the ferromagnetism of Fe3GeTe2 will be completely converted into antiferromagnetism, making it impossible to induce exchange bias or control the exchange bias.

[0019] This invention can solve the problem of insufficient flexibility and thinness of magnetic devices by pressure-controlled exchange bias, and does not require two kinds of antiferromagnetic and ferromagnetic materials. The two different materials need to form exchange coupling, and their atomic structures need to be relatively compatible, which is difficult to construct.

[0020] Preferably, a magnetic field is cyclically applied to the two-dimensional van der Waals magnetic sheet, and a uniaxial pressure perpendicular to the surface of the two-dimensional van der Waals magnetic sheet is repeatedly applied before the exchange bias disappears.

[0021] Beneficial effects: The present invention does not exhibit a decaying training effect by adjusting the exchange bias through pressure. However, after a certain number of cycles of applying the magnetic field, the bias will suddenly disappear. After a large number of experiments, the present invention has found that before the exchange bias disappears, uniaxial pressure perpendicular to the surface of the two-dimensional van der Waals magnetic sheet is repeatedly applied, and the avalanche training effect does not occur. The exchange bias of the two-dimensional van der Waals magnetic sheet remains basically unchanged, thus eliminating the training effect.

[0022] In existing technologies, the switching bias generally relies on magnetic thin films. Due to the presence of numerous magnetic domains and easily magnetized axes, the training effect is gradual and decreases with increasing field application times, and cannot be eliminated.

[0023] Preferably, the pressure applied repeatedly is the same as the pressure applied the first time.

[0024] Preferably, the two-dimensional van der Waals magnetic sheet is Fe3GeTe2.

[0025] Preferably, the organic film is a transparent organic film.

[0026] Beneficial effects: The base film allows pressure to be uniformly transmitted to the sample, while also protecting the sample. Because it is transparent, it is easy to locate the target sample.

[0027] Preferably, the organic film is made of polydimethylsiloxane.

[0028] Preferably, the pressure is maintained for 3-20 minutes and then released.

[0029] Preferably, the first carrier is a silicon wafer.

[0030] Preferably, the second carrier is a glass slide.

[0031] Preferably, the two-dimensional van der Waals magnetic material is thinned by mechanical peeling to form a thin sheet.

[0032] Preferably, the mechanical peeling is performed by repeatedly folding and tearing off adhesive tape.

[0033] The advantages of this invention are:

[0034] Existing exchange bias methods are difficult to control in terms of bias magnitude. Even when an exchange bias can be induced, the magnitude of the exchange bias field cannot be controlled. This invention achieves and controls the magnitude of the exchange bias by adjusting the relative proportions of the thicknesses of the ferromagnetic layer and the antiferromagnetic layer. The higher the proportion of the antiferromagnetic layer, the larger the exchange bias field.

[0035] This invention uses a single two-dimensional magnetic material to induce both antiferromagnetism and ferromagnetism by applying uniaxial pressure perpendicular to the sample surface. While an exchange bias is generated, the magnitude of the exchange bias field can be controlled by setting a pressure within a certain range.

[0036] When the uniaxial pressure is less than 0.1 GPa, an exchange bias cannot be induced, meaning the exchange bias cannot be controlled.

[0037] When the uniaxial pressure is greater than 1 GPa, according to theoretical predictions, the ferromagnetism of Fe3GeTe2 will be completely converted into antiferromagnetism, making it impossible to induce exchange bias or control the exchange bias.

[0038] This invention uses a base film to uniformly transmit pressure to the sample, while the base film also protects the sample. Because it is transparent, it is easy to locate the target sample.

[0039] The present invention does not exhibit a decaying training effect by adjusting the exchange bias through pressure. However, after a certain number of cycles of applying the magnetic field, the bias will suddenly disappear. Through extensive experiments, the present invention has found that before the exchange bias disappears, repeated application of uniaxial pressure perpendicular to the surface of the two-dimensional van der Waals magnetic sheet does not produce an avalanche training effect. The exchange bias of the two-dimensional van der Waals magnetic sheet remains basically unchanged, thus eliminating the training effect.

[0040] In existing technologies, the exchange bias generally relies on magnetic thin films. Due to the presence of many magnetic domains and easily magnetized axes, the training effect is gradual. The exchange bias field gradually decreases with the increase of the number of times the field is applied and cannot be eliminated. Attached Figure Description

[0041] Figure 1 This is a schematic diagram illustrating the principle of the exchange bias effect in the background technology of this invention.

[0042] Figure 2 An optical photograph of Fe3GeTe2 (15 nm) in Example 1 of this invention;

[0043] Figure 3This is a hysteresis loop diagram of Fe3GeTe2 before pressurization in Embodiment 1 of the present invention;

[0044] Figure 4 This is a schematic diagram illustrating the application of a uniaxial pressure perpendicular to the surface of the target sample in an embodiment of the present invention.

[0045] Figure 5 This is a hysteresis loop diagram of Fe3GeTe2 after pressurization in Embodiment 1 of the present invention;

[0046] Figure 6 In Example 1 of this invention, different pressures regulate the exchange bias of Fe3GeTe2 (15nm) to produce different magnitudes.

[0047] Figure 7 In Example 2 of this invention, different pressures regulate the exchange bias of Fe3GeTe2 (12nm) to produce different magnitudes.

[0048] Figure 8 In Example 3 of this invention, different pressures resulted in different magnitudes of exchange bias in Fe3GeTe2 (25nm);

[0049] Figure 9 In Example 4 of this invention, different pressures resulted in different magnitudes of exchange bias in Fe3GeTe2 (137nm);

[0050] Figure 10 This is a graph showing the relationship between the Fe3GeTe2 exchange bias field and the number of times the field is applied, under the condition of a single pressurization in Embodiment 1 of the present invention.

[0051] Figure 11 This is the relationship between the Fe3GeTe2 exchange bias field and the number of times the field is applied, under the condition of three pressurizations in Embodiment 1 of the present invention. Detailed Implementation

[0052] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0053] Unless otherwise specified, all test materials and reagents used in the following examples are commercially available.

[0054] Unless otherwise specified in the embodiments, the techniques or conditions described in the literature in this field or in accordance with the product manual may be followed.

[0055] Example 1

[0056] A two-dimensional van der Waals homogeneous structure with adjustable exchange bias includes two-dimensional van der Waals ferromagnetic layers and two-dimensional van der Waals antiferromagnetic layers stacked on top of each other. The thickness of the ferromagnetic layer and the antiferromagnetic layer are both 2-200 nm, and the thickness ratio of the ferromagnetic layer to the antiferromagnetic layer is x:(1-x), where x ranges from 0.1 to 0.9.

[0057] Example 2

[0058] The method for preparing a two-dimensional van der Waals homostructure with adjustable exchange bias in Example 1 illustrates that some two-dimensional van der Waals magnetic materials (such as CrI3) can exhibit both ferromagnetism (odd number of layers) and antiferromagnetism (even number of layers) due to the parity of the number of layers. For the same material, an odd-thickness layer (ferromagnetic) and an even-thickness layer (antiferromagnetic) of a certain thickness can be dissociated. These two thin layers are then stacked and transferred to obtain a homostructure, thereby achieving exchange bias. The magnitude of the exchange bias field can be controlled by changing the relative ratio of the thicknesses of the ferromagnetic and antiferromagnetic layers.

[0059] Specifically, the following steps are included:

[0060] (1) Obtaining samples with odd and even layers. In a glove box, bulk CrI3 was mechanically peeled off using adhesive tape, and the thin layers were transferred to a silicon wafer. Since the thickness of a single CrI3 layer is 0.7 nm, its thickness could be confirmed using atomic force microscopy (AFM), thus obtaining odd-numbered layers (thickness an odd multiple of 0.7) and even-numbered layers (thickness an even multiple of 0.7). Further, magnetic measurements of the thin layers were performed using magneto-optical Kerr (MOKE) technology. The odd-numbered layers were ferromagnetic, thus exhibiting a magnetic signal, while the even-numbered layers were antiferromagnetic, with a net magnetic moment of zero and no hysteresis signal. Suitable samples with odd-numbered (ferromagnetic) and even-numbered (antiferromagnetic) layers could be obtained based on AFM and MOKE measurements.

[0061] (2) Using a two-dimensional transfer stage and with the help of a transparent organic film (polydimethylsiloxane, PDMS, the viscosity can be changed by adjusting the temperature), align the target odd-numbered (or even-numbered) layer sample with a transparent organic film (polydimethylsiloxane, PDMS, the viscosity can be changed by adjusting the temperature), and adsorb it from the substrate. Then align it with the target even-numbered (or odd-numbered) layer sample and heat it to about 100 degrees Celsius to reduce the viscosity of PDMS and drop the sample down to achieve the stacking of odd-numbered and even-numbered layer samples. Adjust the thickness ratio of the ferromagnetic layer and the antiferromagnetic layer to x:(1-x), where x ranges from 0.1 to 0.9.

[0062] (3) In order to enhance the coupling between the two samples, they were annealed in a vacuum at 150 degrees Celsius for 10 minutes.

[0063] Example 3

[0064] The preparation method of the two-dimensional van der Waals homostructure with adjustable exchange bias in Example 1, which controls the exchange bias of the two-dimensional van der Waals magnetic material and eliminates the training effect by pressure, includes the following steps:

[0065] (1) The blocky two-dimensional van der Waals magnetic material Fe3GeTe2 was thinned by repeatedly folding and tearing off adhesive tape;

[0066] (2) Attach Fe3GeTe2 to a silicon wafer approximately 5 mm thick. After two hours, remove the tape and locate a relatively large (10-200 μm) Fe3GeTe2 thin film on the silicon wafer. The film thickness should be between 5-200 nm; in this example, it is 15 nm. Figure 2 (It is its optical photomicrograph), such as Figure 3 As shown, the Fe3GeTe2 thin film is ferromagnetic, as can be seen from the magneto-optical Kerr test (MOKE).

[0067] (3) Fix the silicon wafer with the target sample onto a three-dimensional moving platform, and position the target sample using a microscope. Attach approximately 2 mm of PDMS (polydimethylsiloxane) to a glass slide, which is then fixed to another three-dimensional displacement platform. Align the PDMS side downwards with the target sample, and adjust the two displacement platforms as needed. Figure 4 As shown, a uniaxial pressure perpendicular to the target sample surface was applied, and the magnitude of the uniaxial vertical pressure was adjusted to 0.1 GPa. After maintaining this pressure for 3 minutes, the pressure was released, yielding the pressurized Fe3GeTe2. Figure 3 and Figure 5 As shown, before pressurization, the Fe3GeTe2 hysteresis loop is only ferromagnetic and has no exchange bias. After pressurization, the Fe3GeTe2 hysteresis loop exhibits both ferromagnetism and antiferromagnetism, indicating the appearance of exchange bias. The exchange bias field H EB It is approximately 450 Oe.

[0068] (4) Adjusting the pressure to control the magnitude of the exchange bias field: By adjusting the upper and lower displacement platforms, uniaxial pressures of 0.1 GPa, 0.15 GPa, and 0.23 GPa are applied vertically to the surface of the target sample, respectively, for 3 minutes each time. Figure 6 As shown, their exchange bias fields are 250 Oe, 420 Oe and 782 Oe, respectively.

[0069] Example 4

[0070] The difference between this embodiment and Embodiment 3 is that the thickness of the Fe3GeTe2 thin film is adjusted to 12 nm. Figure 7 As shown, their exchange bias fields are 290 Oe, 660 Oe and 1000 Oe, respectively.

[0071] Example 5

[0072] The difference between this embodiment and Embodiment 3 is that the thickness of the Fe3GeTe2 thin film was adjusted to 25 nm, and uniaxial pressures of 0.15 GPa and 0.23 GPa were applied vertically to the surface of the target sample, with each application lasting 3 minutes. Figure 8 As shown, their exchange bias fields are 145 Oe and 350 Oe, respectively.

[0073] Example 6

[0074] The difference between this embodiment and Embodiment 3 is that the thickness of the Fe3GeTe2 thin film was adjusted to 137 nm, and uniaxial pressures of 0.23 GPa and 0.40 GPa were applied vertically to the surface of the target sample, with each application lasting 10 minutes. Figure 9 As shown, their exchange bias fields are 15 Oe and 220 Oe, respectively.

[0075] Example 7

[0076] Methods to eliminate the training effect by applying pressure repeatedly

[0077] like Figure 10 As shown, the exchange bias in Example 1 did not exhibit a gradual decay training effect similar to that of the traditional system. However, after more than 20 cycles of applying the magnetic field, the bias suddenly disappeared. Before the bias disappeared, Fe3GeTe2 was subjected to pressure once every 15 cycles of applying the magnetic field, with the pressure application method and time being the same as in step (3). Figure 11 As shown, the avalanche-like training effect did not occur, and the exchange bias of Fe3GeTe2 remained essentially unchanged, eliminating the training effect. Circulating magnetic fields are a standard method for investigating the exchange bias training effect, with a magnetic field strength of 0.5T.

[0078] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A two-dimensional van der Waals homogeneous structure with adjustable exchange bias, characterized in that: The structure comprises two-dimensional van der Waals ferromagnetic layers and two-dimensional van der Waals antiferromagnetic layers stacked on top of each other, with thicknesses ranging from 2 to 200 nm. Uniaxial pressures of varying magnitudes (0.1-1 GPa) are applied perpendicular to the surface of the two-dimensional van der Waals magnetic sheet and maintained for a period of time, resulting in a certain proportion of stacked two-dimensional van der Waals ferromagnetic and antiferromagnetic layers. By setting different magnitudes of uniaxial pressure within a certain range, the magnitude of the exchange bias field can be controlled; as the uniaxial pressure increases from 0.1 to 1 GPa, the magnitude of the exchange bias field increases sequentially. The thickness ratio of the ferromagnetic layer to the antiferromagnetic layer is x : (1-x), where x ranges from 0.1 to 0.

9.

2. The method for preparing a two-dimensional van der Waals homostructure with adjustable exchange bias as described in claim 1, characterized in that: Includes the following steps: Two-dimensional van der Waals ferromagnetic layers with a thickness of 2-200 nm and two-dimensional van der Waals antiferromagnetic layers with a thickness of 2-200 nm are stacked, and the thickness ratio of the ferromagnetic layer to the antiferromagnetic layer is adjusted to x : (1-x), where x ranges from 0.1 to 0.9, to obtain a two-dimensional van der Waals homogeneous structure with adjustable exchange bias.

3. The method for preparing a two-dimensional van der Waals homostructure with adjustable exchange bias as described in claim 1, characterized in that: Includes the following steps: (1) Place a two-dimensional van der Waals magnetic sheet with a thickness of 2-200 nm on a first carrier, attach an organic film to a second carrier, and set the organic film toward the two-dimensional van der Waals magnetic sheet. (2) Apply uniaxial pressure of different magnitudes perpendicular to the surface of the two-dimensional van der Waals magnetic sheet to the organic thin film. The uniaxial pressure is 0.1-1 GPa. Maintain for a period of time to form a two-dimensional van der Waals ferromagnetic layer and a two-dimensional van der Waals antiferromagnetic layer that are superimposed in a certain proportion. The thickness ratio of the ferromagnetic layer and the antiferromagnetic layer is x : (1-x), where x ranges from 0.1 to 0.

9.

4. The method for preparing a two-dimensional van der Waals homostructure with adjustable exchange bias according to claim 3, characterized in that: A magnetic field is cyclically applied to a two-dimensional van der Waals magnetic sheet, and a uniaxial pressure perpendicular to the surface of the two-dimensional van der Waals magnetic sheet is repeatedly applied before the exchange bias disappears.

5. The method for preparing a two-dimensional van der Waals homostructure with adjustable exchange bias according to claim 4, characterized in that: The pressure applied repeatedly is the same as the first time.

6. The method for preparing a two-dimensional van der Waals homostructure with adjustable exchange bias according to claim 3, characterized in that: The two-dimensional van der Waals magnetic sheet is Fe3GeTe2.

7. The method for preparing a two-dimensional van der Waals homostructure with adjustable exchange bias according to claim 3, characterized in that: The organic film is a transparent organic film.

8. The method for preparing a two-dimensional van der Waals homostructure with adjustable exchange bias according to claim 3, characterized in that: Maintain pressure for 3-20 minutes, then release the pressure.

9. The method for preparing a two-dimensional van der Waals homostructure with adjustable exchange bias according to claim 3, characterized in that: The first carrier is a silicon wafer.

10. The method for preparing a two-dimensional van der Waals homostructure with adjustable exchange bias according to claim 3, characterized in that: Two-dimensional van der Waals magnetic materials are thinned to form sheets by mechanical exfoliation.

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