Two-dimensional antiferromagnetic material and preparation method and application thereof

Abstract

The invention discloses a two-dimensional antiferromagnetic material and a preparation method and application thereof, and the method comprises the following steps: adopting Mn and Te elementary substance powder, taking I2 as a transportation agent, and synthesizing a blocky MnTe precursor through a vacuum chemical vapor transport method under a vacuum sealing condition; the preparation method comprises the following steps: mixing a ground MnTe precursor with In elementary substance powder and fluxing agent KCl powder, carrying out fluxing reaction in a vertical confinement space constrained by a constant normal pressure and in an inert atmosphere, and inducing the crystal to epitaxially grow along the horizontal direction, thereby forming a two-dimensional Mn (InTe2) 2 crystal on a fluorine crystal mica substrate, and carrying out wet transfer to obtain the two-dimensional Mn (InTe2) 2 crystal on a SiO2 / Si substrate, according to the method, the two-dimensional Mn (InTe2) 2 crystal with the antiferromagnetic characteristic is prepared through a step-by-step precursor induction type confinement pressure melting epitaxial method, and the method is simple in process and high in repeatability; the two-dimensional Mn (InTe2) 2 crystal has the characteristics of good crystal quality, large transverse size, controllable layer number and the like, and can be applied to a high-density magnetic storage device.

Description

A two-dimensional antiferromagnetic material, its preparation method and application Technical Field

[0001] This invention belongs to the field of nanomagnetic material preparation technology, specifically relating to a two-dimensional antiferromagnetic material, its preparation method, and its application. Background Technology

[0002] In recent years, with the rapid development of spintronics and quantum information technology, two-dimensional magnetic materials have become an important research frontier in materials physics due to their unique layered structure, tunable magnetic ordering behavior, and quantum effects exhibited at the nanoscale. In particular, two-dimensional ferromagnetic and antiferromagnetic materials have broad application potential in high-density magnetic memories, magnetic random access memories, spin valve devices, magneto-optical sensors, and novel quantum computing systems. In traditional magnetic systems, magnetism usually originates from the spin coupling of transition metal ions, but as the material thickness shrinks to the atomic level, magnetic order is often disrupted by thermal fluctuations. To address this, researchers have constructed two-dimensional magnetic material systems with strong spin-orbit coupling and interlayer van der Waals interactions, achieving stable low-dimensional magnetic ordering behavior. However, these materials still suffer from complex and reproducible fabrication methods, often requiring mechanical exfoliation or molecular beam epitaxy, making it difficult to fabricate large-area, controllable-thickness two-dimensional crystals. Furthermore, weak interlayer coupling and insufficient magnetic anisotropy, to some extent, limit the further exploration and application of two-dimensional magnetic materials in high-density magnetic storage devices.

[0003] To overcome these bottlenecks, researchers have begun exploring new antiferromagnetic material systems and methods for preparing their two-dimensional morphologies, aiming to obtain low-dimensional antiferromagnets that possess both high crystallinity and structural stability. Among them, Mn(InTe2)2 is considered an ideal candidate system for realizing two-dimensional antiferromagnetic behavior due to the high magnetic moment and d-orbital spin polarization capability of Mn ions. Recent first-principles calculations have shown that Mn(InTe2)2 has a stable layered noncentrosymmetric crystal structure, with Mn atoms providing localized spin magnetic moments corresponding to half-filled d-orbital states. Under ambient pressure, the energy of its antiferromagnetic configuration is lower than that of its ferromagnetic configuration, thus antiferromagnetic order is its ground-state magnetism (Bose A, Banerjee R, Narayan A. Pressure-induced magnetic and topological transitions in non-centrosymmetric MnIn2Te4[J]. IOP Publishing Ltd, 2024.). This indicates that there is a strong superexchange interaction between the Mn-Te layers, which enables the system to maintain a stable antiferromagnetic spin alignment without an external field, providing a theoretical basis for subsequent experimental research.

[0004] However, current research on the Mn-In-Te system is mainly focused on the theoretical level, lacking a systematic exploration of its experimental feasibility, especially in areas such as the preparation of two-dimensional samples, crystal growth rules, and verification of antiferromagnetic properties. For the Mn-In-Te multi-layered system, the large differences in component volatility and narrow phase stability windows make it difficult to achieve controllable growth of two-dimensional morphology while maintaining stoichiometry using conventional mechanical exfoliation, single-step chemical vapor transport, or simple fluxing methods. This often leads to component segregation, interlayer disorder, or destruction of magnetic order. Therefore, existing fabrication processes for two-dimensional magnetic materials are not directly applicable to the Mn(InTe2)2 system. Thus, there is an urgent need to propose a simple, reproducible method for preparing Mn(InTe2)2 two-dimensional materials that can maintain antiferromagnetic order, enabling the transformation from theoretical prediction to experimental verification and promoting its practical application in fundamental magnetic research and high-density magnetic storage devices. Summary of the Invention

[0005] To overcome the shortcomings of the prior art, the present invention aims to provide a two-dimensional antiferromagnetic material, its preparation method, and its applications. A stepwise precursor strategy is employed, first synthesizing a MnTe precursor to effectively reduce the risk of component segregation during the direct reaction of the multi-component system. The MnTe precursor is mixed with In elemental powder and flux KCl powder, and placed in a vertically confined space under constant normal pressure for fluxing reaction, achieving a stable supply of reactants and inducing two-dimensional preferential epitaxial growth. Under the synergistic effect of constant pressure confinement and fluxing conditions, the number of layers of the two-dimensional Mn(InTe2)2 crystal is controllably grown and the structure is ordered, thereby obtaining a few-layer two-dimensional crystal that maintains antiferromagnetic order. The stepwise precursor-induced confined flux epitaxy (SPI-CFE) method used in this invention is simple and has controllable process parameters. The two-dimensional antiferromagnetic material prepared has high crystal quality, good layer uniformity and stable antiferromagnetic ordered properties, providing a new technical approach for the controllable preparation of two-dimensional antiferromagnetic systems.

[0006] To achieve the above objectives, the technical solution adopted by this invention is as follows: A method for preparing a two-dimensional antiferromagnetic material, using Mn and Te elemental powders, with I2 as a transport agent, to synthesize a bulk MnTe precursor via vacuum chemical vapor transport; the ground MnTe precursor is mixed with In elemental powder and flux KCl powder, and a fluxing reaction is carried out in a vertically confined space under constant normal pressure and in an inert atmosphere to induce the crystal to grow epitaxially along the horizontal direction, thereby forming a two-dimensional Mn(InTe2)2 crystal on a fluorinated mica substrate, and then obtaining a two-dimensional Mn(InTe2)2 crystal on a SiO2 / Si substrate after wet transfer; specifically including the following steps: Step 1: Mixing Mn powder, Te powder and transport agent I2 powder to obtain a mixed Powder I; Step 2: The vacuum-sealed mixed powder I is placed in a dual-temperature zone tube furnace for crystal growth using vacuum chemical vapor transport method to obtain a bulk MnTe precursor; Step 3: The bulk MnTe precursor and flux KCl are ground into powder and mixed evenly with In powder to obtain mixed powder II. Mixed powder II is confined in a vertical confinement space with constant normal pressure using two fluorine mica substrates; Step 4: The confined mixed powder II is subjected to a fluxing reaction in an inert atmosphere to induce the crystal to grow epitaxially in the horizontal direction to obtain a two-dimensional Mn(InTe2)2 crystal with fluorine mica as the substrate; After wet transfer, a two-dimensional Mn(InTe2)2 crystal on a SiO2 / Si substrate is obtained, which is a two-dimensional antiferromagnetic material.

[0007] 2. The method for preparing a two-dimensional antiferromagnetic material according to claim 1, characterized in that: in step 1, the molar ratio of Mn powder to Te powder is 1:(1.2-3) by molar ratio, and the mass of transport agent I2 powder is 6.8%-8% of the total mass of mixed powder I; the purity of Mn powder, Te powder and I2 powder is greater than or equal to 99.9%.

[0008] In step 2, the mixed powder I is vacuum-sealed in a quartz ampoule under liquid nitrogen protection, with the vacuum level inside the sealed quartz ampoule being less than or equal to 10. -4 Pa.

[0009] In step 2, the process of synthesizing the bulk MnTe precursor using vacuum chemical vapor transport is as follows: the temperature control program of the dual-temperature zone tube furnace is started simultaneously. In the raw material zone, the temperature is increased from room temperature to 620-680℃ at 40-60℃ / h and held for 10-20h, then increased to 720-760℃ at 3-6℃ / h and held for 200-240h, and then naturally cooled to room temperature. In the growth zone, the temperature is increased from room temperature to 620-680℃ at 40-60℃ / h and held for 10-20h, then increased to 690-710℃ at 2.1-2.4℃ / h and held for 200-240h, and then naturally cooled to room temperature to obtain the bulk MnTe precursor.

[0010] In step 3, the mass ratio of In, MnTe and KCl is 1:(3-6):(20-40).

[0011] In step 3, the blocky MnTe precursor and the flux KCl are both ground into powder of 200-3000 mesh; the In powder has a particle size of ≥200 mesh and a purity of ≥99.9%.

[0012] In step 4, the vertical confinement space of constant normal pressure constraint is applied by two stacked high-temperature resistant stainless steel circular plates. Mixed powder II covered by two fluorine crystal mica substrates is placed between the two circular plates. The two circular plates are uniformly pressurized by four pairs of bolts and nuts, with each pair of bolts and nuts applying a torque of 3.0-3.5 N·m.

[0013] In step 4, the fluxing reaction process for preparing two-dimensional Mn(InTe2)2 crystals with fluorinated mica as a substrate is as follows: under an argon atmosphere, the temperature is increased from room temperature to 800-900℃ at a rate of 10-20℃ / min, held for 10-20min, and then naturally cooled to room temperature; the argon gas flow rate is 100-300sccm.

[0014] This invention also provides a two-dimensional antiferromagnetic material prepared by the above-described method. The two-dimensional antiferromagnetic material is a nanoscale few-layer two-dimensional nanosheet structure with a thickness of 10-50 nm. The chemical formula of the two-dimensional antiferromagnetic material is Mn(InTe2)2, with lattice constants a = b = 6.31 Å and c = 12.55 Å, belonging to the tetragonal crystal system. Space group.

[0015] The present invention also provides the application of the two-dimensional antiferromagnetic material prepared by the above preparation method in high-density magnetic storage devices.

[0016] Compared with existing technologies, this invention has the following advantages: 1. By preparing a MnTe precursor before flux-induced two-dimensional epitaxial growth and introducing In elements to participate in the reconstruction growth during subsequent reactions, the Mn-Te related chemical bonds and local chemical potentials in the reaction system are effectively constrained and buffered in the early stages of growth, thereby avoiding the simultaneous disorderly competitive reactions of Mn, In, and Te elements in a high-temperature flux environment. Through the above-mentioned stepwise precursor-induced preparation strategy, this invention significantly improves the stability and consistency of the overall stoichiometry during growth, reduces the fluctuation range of elemental ratios between different growth regions, and facilitates the controllable preparation of target two-dimensional Mn(InTe2)2 crystals with uniform composition and stable structure. In addition, this method can effectively narrow the formation window of the target phase and improve the repeatability and predictability of the reaction path, thereby facilitating the acquisition of two-dimensional antiferromagnetic materials with stable layered structures and consistent physical properties, providing a reliable material basis for subsequent device fabrication and performance regulation.

[0017] 2. This invention employs a constant-pressure clamp during the fluxing reaction process to apply constant pressure to the fluorinated mica substrate, thereby constructing a stable confined growth space at the reaction interface. This allows the reactants and flux to spread and migrate within a restricted vertical space, effectively suppressing disordered material growth along the thickness direction. The constant-pressure confined growth method of this invention significantly improves the two-dimensional tendency of the crystal growth process, making it easier for the product to spread and grow in a continuous sheet-like structure on the substrate surface, reducing the generation of granular or agglomerated deposits, and thus improving the consistency and controllability of the product morphology. Furthermore, the constant-pressure confinement condition helps stabilize the growth environment, reduces the randomness of the growth process, and improves the repeatability and predictability of the preparation results, thus providing a reliable process guarantee for obtaining two-dimensional Mn(InTe2)2 crystal materials with stable morphology and controllable structure.

[0018] 3. This invention utilizes fluorinated mica as the growth substrate and combines it with a constant-pressure confined fluxing reaction method. It fully leverages the smooth surface of fluorinated mica and the relatively mild interfacial interaction of its layered cleavage planes to provide a more stable interfacial environment for the nucleation and lateral expansion of the target crystal on the substrate surface, thereby reducing the competitive growth phenomenon caused by discrete high-density nucleation. Through the synergistic effect of the selected fluorinated mica substrate and the confined fluxing process, this invention significantly improves the continuous spreading ability and lateral size controllability of two-dimensional Mn(InTe2)2 crystals on the substrate surface. This facilitates the acquisition of two-dimensional crystal materials with more regular morphology, better continuity, and higher repeatability, providing a reliable material basis for subsequent transfer, device fabrication, and performance consistency characterization.

[0019] 4. Compared with traditional mechanical exfoliation methods, this invention grows few-layer two-dimensional Mn(InTe2)2 crystals on a fluorine-crystal mica substrate using the SPI-CFE method and then transfers them to a SiO2 / Si substrate via a wet process. This successfully reduces the Mn(InTe2)2 material from a three-dimensional bulk shape to a two-dimensional size with nanometer-level thickness. The prepared two-dimensional Mn(InTe2)2 crystals have the characteristics of high crystallinity, large lateral size, and thin number of layers.

[0020] In summary, this invention employs a stepwise precursor-induced confined pressure-containment epitaxy method. First, high-purity Mn and Te elements are reacted with transport agent I2 under vacuum-sealed conditions to prepare bulk MnTe precursor crystals. Then, using the MnTe precursor as a reaction source, In elemental powder and flux are introduced under constant pressure confinement conditions. Through a fluxing reaction, two-dimensional preferential epitaxial growth is induced, forming few-layer two-dimensional Mn(InTe2)2 crystals on a fluorinated mica substrate. Further wet transfer yields two-dimensional Mn(InTe2)2 crystal material on a SiO2 / Si substrate. The preparation process of this invention, through the synergistic control of stepwise reaction and constant pressure confinement conditions, achieves stable feed of the reaction system and controllable growth of the two-dimensional structure, which is beneficial for obtaining two-dimensional Mn(InTe2)2 crystals with good crystal quality and ordered structure. The Mn(InTe2)2 crystal prepared by this invention has lattice constants a = b = 6.31 Å and c = 12.55 Å, belonging to the tetragonal crystal system. The space group is approximately 20 K, exhibiting typical antiferromagnetic properties. The obtained two-dimensional Mn(InTe2)2 crystal possesses advantages such as high crystallinity, large lateral dimensions, and thin layers, providing a reliable two-dimensional preparation method for material systems where interlayer cleavage is difficult to achieve through conventional mechanical exfoliation methods. Attached Figure Description

[0021] Figure 1 is a schematic diagram of the structure of a two-dimensional Mn(InTe2)2 crystal; where (a) in Figure 1 is a view of plane a, (b) in Figure 1 is a view of plane b, and (c) in Figure 1 is a view of plane c.

[0022] Figure 2 shows an optical image of the MnTe precursor prepared by the CVT process.

[0023] Figure 3 is a schematic diagram of the pressure fixture used in the preparation of two-dimensional Mn(InTe2)2 crystals.

[0024] Figure 4 is a flowchart of a wet transfer process suitable for transferring two-dimensional Mn(InTe2)2 crystals between substrates.

[0025] Figure 5 shows the local morphology and EDS elemental distribution and quantification results of the sample prepared in Comparative Example 1 at two different locations; in Figure 5, (a) is the SEM image of location 1, (b) is the In elemental distribution map of location 1, (c) is the Mn elemental distribution map of location 1, (d) is the Te elemental distribution map of location 1, (e) is the SEM image of location 2, (f) is the In elemental distribution map of location 2, (g) is the Mn elemental distribution map of location 2, and (h) is the Te elemental distribution map of location 2.

[0026] Figure 6 is an optical microscope image of the sample prepared in Comparative Example 2.

[0027] Figure 7 is an optical microscope image of the sample prepared in Comparative Example 3.

[0028] Figure 8 shows an optical microscope image of the sample prepared in Comparative Example 4; in Figure 8, (a) is an optical microscope image after one mechanical peeling, and (b) is an optical microscope image after ten mechanical peelings.

[0029] Figure 9 is an optical microscope image of the two-dimensional Mn(InTe2)2 crystal prepared in Example 2 with fluorinated mica as a substrate.

[0030] Figure 10 is an optical microscope image of the two-dimensional Mn(InTe2)2 crystal prepared in Example 2 and transferred to a SiO2 / Si substrate by wet transfer.

[0031] Figure 11 is a comparison between the experimental XRD pattern of the two-dimensional Mn(InTe2)2 crystal prepared in Example 2 and the reference simulated XRD pattern.

[0032] Figure 12 shows the EDS spectrum of the two-dimensional Mn(InTe2)2 crystal prepared in Example 2; wherein, (a) in Figure 12 is the SEM image, (b) in Figure 12 is the In element distribution map, (c) in Figure 12 is the Te element distribution map, and (d) in Figure 12 is the Mn element distribution map.

[0033] Figure 13 shows the AFM diagram and MFM phase shift diagram of the two-dimensional Mn(InTe2)2 crystal prepared in Example 2; wherein, Figure 13(a) is the AFM diagram and Figure 13(b) is the MFM phase shift diagram.

[0034] Figure 14 shows the magnetic susceptibility of the two-dimensional Mn(InTe2)2 crystal prepared in Example 2 as a function of temperature (χ-T).

[0035] Figure 15 shows the curve of the dimagnetic susceptibility of the two-dimensional Mn(InTe2)2 crystal prepared in Example 2 as a function of temperature (1 / χ-T). Detailed Implementation

[0036] To enable those skilled in the art to better understand the present invention, the technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0037] As shown in Figure 1, a two-dimensional antiferromagnetic material is described. This material has a few-layer two-dimensional nanosheet crystal structure, with the chemical formula Mn(InTe2)2, and its lattice constants are a = b = 6.31 Å and c = 12.55 Å. It belongs to the tetragonal crystal system. Space group. The two-dimensional Mn(InTe2)2 crystal is a nanoscale few-layer two-dimensional nanosheet structure with a thickness of 10-50 nm.

[0038] A method for preparing a two-dimensional antiferromagnetic material employs a stepwise precursor-induced confined pressure melting epitaxy method. First, bulk MnTe precursor crystals are synthesized using Mn and Te elemental powders as raw materials via vacuum chemical vapor transport (CVT) under the action of transport agent I2. Subsequently, the MnTe precursor is ground into powder and mixed with In elemental powder and flux KCl powder. A fluxing reaction is then carried out in an inert atmosphere within a vertically confined space constrained by constant normal pressure, inducing the crystal to grow epitaxially along the horizontal direction, thereby forming a two-dimensional Mn(InTe2)2 crystal on a fluorinated mica substrate. After wet transfer, a few-layer two-dimensional crystal on a SiO2 / Si substrate is obtained. Mn(InTe2)2 crystal, i.e., two-dimensional antiferromagnetic material; specifically including the following steps: Step 1: Mix Mn powder, Te powder and transport agent I2 powder to obtain mixed powder I; according to the molar ratio, the ratio of Mn powder to Te powder is 1:(1.2-3), and the mass of transport agent I2 powder is 6.8%-8% of the total mass of mixed powder I; the purity of Mn powder, Te powder and I2 powder is greater than or equal to 99.9%; Step 2: Vacuum seal mixed powder I in a quartz ampoule under liquid nitrogen protection; the vacuum sealing process is as follows: use a molecular pump and an oxyhydrogen flame gun to vacuum seal the quartz ampoule, and the vacuum degree inside the sealed quartz ampoule is less than or equal to 10. -4Pa; Step 3: Place the vacuum-sealed quartz ampoule in a dual-temperature zone tube furnace for crystallization growth. The temperature of the dual-temperature zone is controlled by a program to ensure sufficient reaction between the components in mixed powder I, synthesizing a bulk MnTe precursor with a gray metallic luster, as shown in Figure 2. The specific process of synthesizing the bulk MnTe precursor using the vacuum chemical vapor transport method is as follows: Simultaneously start the temperature control program of the dual-temperature zone tube furnace, wherein the raw material zone temperature is increased from room temperature to 40°C. The temperature is increased at 60℃ / h to 620-680℃ and held for 10-20h. Then, the temperature is increased at 3-6℃ / h to 720-760℃ and held for 200-240h, followed by natural cooling to room temperature. In the growth zone, the temperature is increased from room temperature to 620-680℃ at 40-60℃ / h and held for 10-20h. Then, the temperature is increased at 2.1-2.4℃ / h to 690-710℃ and held for 200-240h, followed by natural cooling to room temperature.

[0039] Step 4: Grind the bulk MnTe precursor and flux KCl separately to a fine powder of 200-3000 mesh. Then, mix In powder, MnTe and KCl uniformly at a mass ratio of 1:(3-6):(20-40) to obtain mixed powder II. Place the mixed powder II between two fluorine mica substrates to assemble a "sandwich" structure. Use a pressure clamp to uniformly press the mixed powder II between the two fluorine mica substrates, confining it within a vertically confined space under constant normal pressure. The In powder has a particle size greater than or equal to 200 mesh and a purity greater than or equal to 99.9%. As shown in Figure 3, the pressure clamp used to prepare the two-dimensional Mn(InTe2)2 crystal is a self-made high-temperature resistant stainless steel clamp that can withstand a high temperature of 1200℃. The pressure clamp includes two... High-temperature resistant stainless steel discs are stacked, with a fluorinated mica substrate placed between two discs. The two discs are connected and uniformly pressed together by four pairs of evenly distributed bolts and nuts. The stainless steel discs are 18mm in diameter and 2mm thick, with four symmetrical holes for M3 bolts. By applying a torque of 3.0-3.5 N·m to each pair of bolts and nuts, a stable and repeatable clamping force is generated between the two discs, thereby reducing the distance between the two fluorinated mica substrates and achieving a spatial confinement effect, which facilitates the preferential growth of the material along the two-dimensional direction. The symmetrical distribution of the four pairs of bolts and nuts in the plane allows for the uniform transfer of clamping force to the interlayer mixed powder II, improving the uniformity of force distribution and the parallelism of the contact surface, thus suppressing disordered deposition in the thickness direction and promoting the preferential growth of the material along the two-dimensional direction. The fluorinated mica substrate used is a square with a side length of 10mm, used for growing two-dimensional Mn(InTe2)2 crystals.

[0040] Step 5: The confined mixed powder II is placed in a tube furnace and subjected to a fluxing reaction under a flowing argon atmosphere. The temperature of the tube furnace is controlled by a program to ensure that the raw material is fully melted under the action of flux KCl, inducing the crystal to grow epitaxially in the horizontal direction. Then, it is naturally cooled to room temperature to allow the raw material to fully crystallize, resulting in a few-layer two-dimensional Mn(InTe2)2 crystal with fluorinated mica as a substrate. After wet transfer, a few-layer two-dimensional Mn(InTe2)2 crystal on a SiO2 / Si substrate is obtained, which is a two-dimensional antiferromagnetic material.

[0041] The fluxing reaction process for preparing the two-dimensional Mn(InTe2)2 crystal is as follows: the temperature control program of the tube furnace is started, and the temperature is increased from room temperature to 800-900℃ at a rate of 10-20℃ / min, and held for 10-20min to allow the raw material to fully melt under the action of flux KCl. Then, it is naturally cooled to room temperature to allow the raw material to fully crystallize. The entire process is carried out under an argon atmosphere with an argon gas flow rate of 100-300 sccm.

[0042] As shown in Figure 4, the wet transfer process is as follows: S1: Fix the fluorinated mica substrate with two-dimensional Mn(InTe2)2 crystals grown on a dry and clean glass slide, add two drops of polymethyl methacrylate (PMMA), spin coat at 1000 r / min for 20 s, then spin coat at 4000 r / min for 30 s, and then anneal on a 180°C hot plate for 5 min to ensure close adhesion between PMMA and the surface of the two-dimensional Mn(InTe2)2 crystals; then immerse it in a 5% hydrofluoric acid solution for 120 min, achieving selective etching of the fluorinated mica substrate by precisely controlling the etching time; S2: Place the selectively etched two-dimensional Mn(InTe2)2 crystals into deionized water, and gently remove the adhering Mn(InTe2)2 crystals... The PMMA film on the two-dimensional Mn(InTe2)2 crystal was peeled off and laid flat on a clean silicon substrate with an oxide layer. It was then annealed at 180°C for 5 min to enhance interfacial adhesion. Finally, the PMMA film on the two-dimensional Mn(InTe2)2 crystal was dissolved and removed in a fume hood using acetone vapor. S3: The sample was washed twice in a beaker containing alcohol to remove acetone. The sample was then washed twice in deionized water to remove alcohol. The sample was then dried at 50°C for 15 min. Finally, it was annealed at 300°C for 2 h under argon protection to further remove organic polymer residues on the surface of the two-dimensional material, and finally, a two-dimensional Mn(InTe2)2 crystal on a SiO2 / Si substrate was obtained, which is a two-dimensional antiferromagnetic material.

[0043] Example 1: A method for preparing a two-dimensional antiferromagnetic material, comprising the following steps: Step 1: 43 mg of Mn powder and 300 mg of Te powder (n Mn : n Te=1:3) and 30mg of I2 powder to form mixed powder I; Step 2: Vacuum seal the mixed powder in a quartz ampoule under liquid nitrogen protection; Step 3: Place the sealed quartz ampoule in a dual-temperature zone tube furnace for crystal growth to obtain a blocky MnTe precursor with gray metallic luster; Specifically: Simultaneously start the temperature control program of the dual-temperature zone tube furnace, wherein the raw material zone is heated from room temperature to 620℃ at 40℃ / h and held for 20h, then heated to 720℃ at 3℃ / h and held for 240h, and then naturally cooled to room temperature; the growth zone is heated from room temperature to 620℃ at 40℃ / h and held for 20h, then heated to 690℃ at 2.1℃ / h and held for 240h, and then naturally cooled to room temperature to obtain the product; Step 4: Thoroughly grind the blocky MnTe precursor and flux KCl separately. The powder was ground to 200 mesh, and then In powder, MnTe and KCl were uniformly mixed in a mass ratio of 1:3:20 to obtain mixed powder II. The mixed powder II was placed between two fluorine mica substrates. The mixed powder II between the two fluorine mica substrates was confined in a vertical confinement space with constant normal pressure by applying a torque of 3.0 N·m to each pair of bolts and nuts of the pressure clamp. Step 5: The confined mixed powder II was placed in a tube furnace and heated from room temperature to 800℃ at 10℃ / min under an argon atmosphere with a gas flow rate of 100 sccm. The temperature was held for 20 min to carry out a fluxing reaction to obtain a few-layer two-dimensional Mn(InTe2)2 crystal with fluorine mica as the substrate. After wet transfer, a few-layer two-dimensional Mn(InTe2)2 crystal on a SiO2 / Si substrate was obtained, which is a two-dimensional antiferromagnetic material.

[0044] Example 2: A method for preparing a two-dimensional antiferromagnetic material, comprising the following steps: Step 1: Mixing 65 mg of Mn powder and 300 mg of Te powder (n Mn : n Te=1:2) and 30mg of I2 powder to form mixed powder I; Step 2: Vacuum seal the mixed powder in a quartz ampoule under liquid nitrogen protection; Step 3: Place the sealed quartz ampoule in a dual-temperature zone tube furnace for crystal growth to obtain a blocky MnTe precursor with gray metallic luster; Specifically: Simultaneously start the temperature control program of the dual-temperature zone tube furnace, wherein the raw material zone is heated from room temperature to 640℃ at 50℃ / h and held for 15h, then heated to 740℃ at 4℃ / h and held for 230h, and then naturally cooled to room temperature; the growth zone is heated from room temperature to 640℃ at 50℃ / h and held for 15h, then heated to 700℃ at 2.4℃ / h and held for 230h, and then naturally cooled to room temperature to obtain the precursor; Step 4: Thoroughly grind the blocky MnTe precursor and flux KCl separately. The powder was ground to 1000 mesh, and then In powder, MnTe and KCl were uniformly mixed in a mass ratio of 1:4:28 to obtain mixed powder II. The mixed powder II was placed between two fluorine mica substrates. The mixed powder II between the two fluorine mica substrates was confined in a vertical confinement space with constant normal pressure by applying a torque of 3.2 N·m to each pair of bolts and nuts of the pressure clamp. Step 5: The confined mixed powder II was placed in a tube furnace and heated from room temperature to 850℃ at 15℃ / min under an argon atmosphere with a gas flow rate of 200 sccm. The temperature was held for 15 min to carry out a fluxing reaction to obtain a few-layer two-dimensional Mn(InTe2)2 crystal with fluorine mica as the substrate. After wet transfer, a few-layer two-dimensional Mn(InTe2)2 crystal on a SiO2 / Si substrate was obtained, which is a two-dimensional antiferromagnetic material.

[0045] Example 3: A method for preparing a two-dimensional antiferromagnetic material, comprising the following steps: Step 1: 95 mg of Mn powder and 300 mg of Te powder (n Mn : n Te=1:1.4) is mixed with 30mg of I2 powder to form mixed powder I; Step 2: The mixed powder is vacuum sealed in a quartz ampoule under liquid nitrogen protection; Step 3: The sealed quartz ampoule is placed in a dual-temperature zone tube furnace for crystal growth to obtain a blocky MnTe precursor with a gray metallic luster; Specifically: The temperature control program of the dual-temperature zone tube furnace is started simultaneously, wherein the raw material zone is heated from room temperature to 660℃ at 50℃ / h and held for 15h, then heated to 750℃ at 5℃ / h and held for 220h, and then naturally cooled to room temperature; the growth zone is heated from room temperature to 660℃ at 50℃ / h and held for 15h, then heated to 700℃ at 2.2℃ / h and held for 220h, and then naturally cooled to room temperature to obtain the product; Step 4: The blocky MnTe precursor and flux KCl are fully mixed separately. The powder was ground to 2000 mesh, and then In powder, MnTe and KCl were uniformly mixed in a mass ratio of 1:5:32 to obtain mixed powder II. The mixed powder II was placed between two fluorine mica substrates. The mixed powder II between the two fluorine mica substrates was confined in a vertical confinement space with constant normal pressure by applying a torque of 3.4 N·m to each pair of bolts and nuts of the pressure clamp. Step 5: The confined mixed powder II was placed in a tube furnace and heated from room temperature to 850℃ at 20℃ / min under an argon atmosphere with a gas flow rate of 200 sccm. The temperature was held for 15 min to carry out a fluxing reaction to obtain a few-layer two-dimensional Mn(InTe2)2 crystal with fluorine mica as the substrate. After wet transfer, a few-layer two-dimensional Mn(InTe2)2 crystal on a SiO2 / Si substrate was obtained, which is a two-dimensional antiferromagnetic material.

[0046] Example 4: A method for preparing a two-dimensional antiferromagnetic material, comprising the following steps: Step 1: Mixing 108 mg of Mn powder and 300 mg of Te powder (n Mn : n Te=1:1.2) is mixed with 30mg of I2 powder to form mixed powder I; Step 2: The mixed powder is vacuum sealed in a quartz ampoule under liquid nitrogen protection; Step 3: The sealed quartz ampoule is placed in a dual-temperature zone tube furnace for crystal growth to obtain a blocky MnTe precursor with a gray metallic luster; Specifically: The temperature control program of the dual-temperature zone tube furnace is started simultaneously, wherein the raw material zone is heated from room temperature to 680℃ at 60℃ / h and held for 10h, then heated to 760℃ at 6℃ / h and held for 200h, and then naturally cooled to room temperature; the growth zone is heated from room temperature to 680℃ at 60℃ / h and held for 10h, then heated to 710℃ at 2.25℃ / h and held for 200h, and then naturally cooled to room temperature to obtain the precursor; Step 4: The blocky MnTe precursor and flux KCl are fully mixed separately. Grind the powder to 3000 mesh, then mix In powder, MnTe and KCl uniformly in a mass ratio of 1:6:40 to obtain mixed powder II, and place it between two fluorine mica substrates. By applying a torque of 3.5 N·m to each pair of bolts and nuts of the pressure clamp, the mixed powder II between the two fluorine mica substrates is confined in a vertical confinement space with constant normal pressure constraint. Step 5: Place the confined mixed powder II in a tube furnace under an argon atmosphere with a gas flow rate of 300 sccm, heat it from room temperature to 900℃ at 20℃ / min, hold it at 10min, and carry out a fluxing reaction to obtain a few-layer two-dimensional Mn(InTe2)2 crystal with fluorine mica as the substrate. After wet transfer, a few-layer two-dimensional Mn(InTe2)2 crystal on a SiO2 / Si substrate is obtained, which is a two-dimensional antiferromagnetic material.

[0047] Comparative Example 1: The preparation conditions of Comparative Example 1 are basically the same as those of Example 2, except that MnTe precursor was not used. Instead, Mn powder, Te powder and In powder were directly mixed and placed together with flux KCl in a vertical confinement space under constant normal pressure constraint. The fluxing reaction was carried out under high temperature conditions, thereby inducing crystal to grow epitaxially in the horizontal direction on the fluorine mica substrate, and the sample of Comparative Example 1 was obtained.

[0048] Two different locations on the obtained sample were selected for local magnified SEM observation, EDS surface distribution, and quantitative analysis, as shown in Figure 5. The SEM images show the magnified morphology of a local crystal region, with visible striped, step-like textures on the surface. EDS surface distribution results indicate that within their respective test fields of view, the In, Mn, and Te elemental signals are generally uniformly distributed, without obvious macroscopic stripe separation. However, EDS quantitative results show significant differences in the atomic percentages of elements at different locations: at location 1, the atomic percentages of Mn, In, and Te are 51.82%, 17.16%, and 31.02%, respectively, while at location 2, the percentages are 35.20%, 13.74%, and 51.06%. The EDS quantitative results suggest that in the absence of a pre-formed MnTe precursor structure, Mn, In, and Te simultaneously participate in the reaction in a high-temperature fluxing environment, easily triggering competing reaction pathways. This leads to significant compositional drift and insufficient consistency in the sample on a larger scale, which is detrimental to the formation of a stable and uniform two-dimensional Mn(InTe2)2 crystal.

[0049] Comparative Example 2 was prepared under essentially the same conditions as Example 2, except that in step 4, a constant pressure was not applied to the fluorine mica sheet to form a confined space. Specifically, the In powder, MnTe precursor, and flux KCl powder mixed according to the proportions in Example 2 were placed on the surface of a fluorine mica substrate, and another fluorine mica sheet was used to cover it to form a sandwich structure. However, no constant pressure fixture was used to apply external pressure to the two mica sheets. The high-temperature fluxing reaction was carried out only under the same atmosphere, heating program, and holding time. The sample was then naturally cooled to room temperature to obtain the sample of Comparative Example 2.

[0050] The obtained samples were observed using an optical microscope, and the results are shown in Figure 6. It can be seen that, under the condition of not forming a constant-pressure confinement space, the material on the substrate surface mainly appears as black granules, randomly distributed and of uneven size. No two-dimensional plate-like crystal structure with continuous spreading characteristics was observed, indicating that the material tends to precipitate in a granular manner under this condition.

[0051] Comparative Example 3 was prepared under essentially the same conditions as Example 2, except that in step 4, the substrate was replaced with a thin quartz substrate instead of a fluorine mica substrate. All other process conditions, including raw material ratios, flux type and amount, constant pressure confinement method, heating program, and holding time, remained consistent with Example 2. Specifically, the In powder, MnTe precursor, and flux KCl powder mixed according to the ratio in Example 2 were placed on the surface of a thin quartz substrate, and a high-temperature fluxing reaction and growth were carried out within a vertically confined space constrained by constant normal pressure. After cooling, the sample of Comparative Example 3 was obtained.

[0052] The obtained samples were observed under an optical microscope, as shown in Figure 7. It can be seen that on the thin quartz substrate, the product mainly exhibits a large number of discretely distributed bright-colored short strip structures, with small overall size and poor continuity, failing to form a large-area continuously spread plate-like crystal morphology. These results indicate that, under the same constant-pressure confinement and fluxing reaction conditions, thin quartz sheets as substrates are more prone to high-density discrete nucleation and restrict lateral expansion, which is detrimental to obtaining large-size, regularly morphologically regular two-dimensional Mn(InTe2)2 crystals.

[0053] Comparative Example 4 uses the same raw material system and target material as Example 2, except that the stepwise precursor-induced constant-pressure flux epitaxy process of this invention was not used to prepare the two-dimensional crystal. Instead, bulk Mn(InTe2)2 crystals were first prepared separately using vacuum chemical vapor transport, and then a two-dimensional treatment was attempted using a traditional mechanical exfoliation method. Specifically, In, Mn, and Te elemental powders were used as raw materials, and I2 was introduced as a transport agent. Bulk Mn(InTe2)2 crystals were synthesized under vacuum sealing conditions using vacuum chemical vapor transport. Subsequently, the surface of the bulk Mn(InTe2)2 crystals was covered with tape, and repeated mechanical exfoliation was performed by applying pressure and quickly tearing off the tape in an attempt to obtain a thin-layer two-dimensional crystal.

[0054] However, for Mn(InTe2)2 materials, this mechanical exfoliation method is difficult to achieve effective interlayer cleavage. As shown in Figure 8, by comparing the optical microscope images of the crystal after one exfoliation in Figure 8(a) and the crystal after ten exfoliations in Figure 8(b), it can be seen that as the number of exfoliations increases, the crystal thickness does not show a significant thinning trend. Instead, it breaks along random cracks, forming smaller irregular fragments, resulting in a continuous decrease in the lateral size of the crystal and difficulty in maintaining the integrity of the lamellae. The above results indicate that the traditional mechanical exfoliation method is not suitable for the two-dimensional preparation of Mn(InTe2)2 materials, and it is difficult to obtain large-area, thickness-controllable, and structurally intact two-dimensional Mn(InTe2)2 crystals.

[0055] As shown in Figure 9, an optical microscope image of a two-dimensional Mn(InTe2)2 crystal with fluorinated mica as a substrate shows that the preparation method of the present invention can obtain regular single crystals with a lateral dimension of more than 100 μm and different layer thicknesses, indicating that the SPI-CFE method can prepare single crystal materials of different thicknesses, providing strong support for the growth of two-dimensional crystals.

[0056] As shown in Figure 10, an optical microscope image of a two-dimensional Mn(InTe2)2 crystal transferred to a SiO2 / Si substrate by wet transfer is obtained. By comparing the optical microscope images of the material before and after transfer (Figure 9), it can be observed that the material was transferred to the SiO2 / Si substrate over a large area, indicating the feasibility of this wet transfer method for two-dimensional Mn(InTe2)2 material.

[0057] Figure 11 shows the comparison between the XRD experimental spectrum of the two-dimensional Mn(InTe2)2 crystal prepared in this invention and the reference simulated spectrum. The red curve represents the XRD experimental results of the sample prepared in this invention, and the blue curve represents the simulated XRD spectrum obtained by density functional theory calculation based on the Mn(InTe2)2 crystal structure provided by the MaterialsProject database (see "The Materials Project: A materials genome approach to accelerating materials innovation" (APL Materials, 2013, 1011002)). As can be seen from Figure 11, the main diffraction peaks of the two-dimensional Mn(InTe2)2 crystal prepared in this invention at 2θ = 24.2°, 41.2°, 43.7°, and 48.1° correspond to the (112), (204), (222), and (312) crystal planes of the Mn(InTe2)2 crystal, respectively, and their peak positions are consistent with the corresponding diffraction peak positions in the simulated XRD spectrum. The above experimental results show that the two-dimensional material prepared by the present invention is consistent with the theoretical calculation results of Mn(InTe2)2 crystal in terms of crystal structure characteristics. The material prepared by the present invention is the target two-dimensional Mn(InTe2)2 crystal, and the crystal has highly oriented crystal plane arrangement and good crystal quality.

[0058] As shown in the EDS spectrum of the two-dimensional Mn(InTe2)2 crystal in Figure 12, the elemental distribution of the material prepared by this invention is uniform, further confirming that the main component of the material is the In-Mn-Te ternary system.

[0059] As shown in Figure 13, the AFM and MFM phase shift diagrams of the two-dimensional Mn(InTe2)2 crystal reveal a smooth sample surface without obvious defects or contamination, exhibiting excellent crystal quality. The crystal has a uniform thickness, averaging approximately 17.2 nm, with clearly visible interlayer steps, consistent with typical characteristics of two-dimensional layered materials. MFM phase analysis reveals a significant phase shift difference (ΔΦ = 0.026°) between the material region and the SiO2 / Si substrate, with sharp phase transitions at the material boundary, indicating a detectable difference in magnetic properties between the Mn(InTe2)2 prepared in this invention and the SiO2 / Si substrate.

[0060] As shown in Figure 14, the temperature-dependent magnetic susceptibility curve of the two-dimensional Mn(InTe2)2 crystal is as follows: at the Nehr temperature T... N A significant anomaly appears at approximately 20 K, corresponding to the antiferromagnetic order transition of the material. In the high-temperature region, χ(T) exhibits Curie-Weiss behavior, indicating that the system is in a paramagnetic state; as the temperature approaches T... NThe curve shows an inflection point and reaches a peak, indicating that long-range antiferromagnetic coupling is gradually established between the spins. After further cooling, the magnetic susceptibility decreases rapidly, showing a reduction in net magnetic moment due to the antiparallel spin arrangement, indicating that the sample has typical antiferromagnetic characteristics.

[0061] As shown in Figure 15, the 1 / χ-T curve exhibits a good linear relationship above approximately 60 K, conforming to the Curie-Weiss law, indicating that the system is paramagnetic in the high-temperature region. The fitted Curie-Weiss temperature θ is negative, indicating that the system is dominated by intrinsic antiferromagnetic exchange interaction. Below 60 K, the curve begins to deviate from linearity, reflecting the gradual formation of short-range spin correlations in the system, and the appearance of a long-range antiferromagnetic order transition at approximately 20 K, which is completely consistent with the χ-T curve results. Therefore, the Mn(InTe2)2 prepared in this invention exhibits Curie-Weiss type paramagnetism at high temperatures, while forming a stable antiferromagnetic ground state at low temperatures.

Claims

1. A method for preparing a two-dimensional antiferromagnetic material, characterized in that: A bulk MnTe precursor was synthesized using Mn and Te elemental powders and I2 as a transport agent via vacuum chemical vapor transport. The ground MnTe precursor was then mixed with In elemental powder and flux powder KCl, and a fluxing reaction was carried out in a vertically confined space under constant normal pressure and an inert atmosphere to induce horizontal epitaxial growth of the crystal, thereby forming a two-dimensional Mn(InTe2)2 crystal on a fluorinated mica substrate. After wet transfer, a two-dimensional Mn(InTe2)2 crystal on a SiO2 / Si substrate was obtained. The specific steps include: Step 1: Mixing Mn powder, Te powder, and I2 powder to obtain mixed powder I; Step 2: Using vacuum chemical vapor transport... Step 1: The vacuum-sealed mixed powder I is placed in a dual-temperature zone tube furnace for crystal growth to obtain a bulk MnTe precursor; Step 2: The bulk MnTe precursor and flux KCl are ground into powder and mixed evenly with In powder to obtain mixed powder II. Mixed powder II is confined in a vertical confinement space with constant normal pressure using two fluorine mica substrates; Step 3: The confined mixed powder II is subjected to a fluxing reaction in an inert atmosphere to induce the crystal to grow epitaxially in the horizontal direction to obtain a two-dimensional Mn(InTe2)2 crystal with fluorine mica as the substrate; After wet transfer, a two-dimensional Mn(InTe2)2 crystal on a SiO2 / Si substrate is obtained, which is a two-dimensional antiferromagnetic material.

2. The method for preparing a two-dimensional antiferromagnetic material according to claim 1, characterized in that: In step 1, the molar ratio of Mn powder to Te powder is 1:(1.2-3) according to the molar ratio, and the mass of transport agent I2 powder is 6.8%-8% of the total mass of mixed powder I; the purity of Mn powder, Te powder and I2 powder is greater than or equal to 99.9%.

3. The method for preparing a two-dimensional antiferromagnetic material according to claim 1, characterized in that: In step 2, the mixed powder I is vacuum-sealed in a quartz ampoule under liquid nitrogen protection, with the vacuum level inside the sealed quartz ampoule being less than or equal to 10. - 4 Pa.

4. The method for preparing a two-dimensional antiferromagnetic material according to claim 1, characterized in that, In step 2, the process of synthesizing the bulk MnTe precursor using vacuum chemical vapor transport is as follows: the temperature control program of the dual-temperature zone tube furnace is started simultaneously. In the raw material zone, the temperature is increased from room temperature to 620-680℃ at 40-60℃ / h and held for 10-20h, then increased to 720-760℃ at 3-6℃ / h and held for 200-240h, and then naturally cooled to room temperature. In the growth zone, the temperature is increased from room temperature to 620-680℃ at 40-60℃ / h and held for 10-20h, then increased to 690-710℃ at 2.1-2.4℃ / h and held for 200-240h, and then naturally cooled to room temperature to obtain the bulk MnTe precursor.

5. The method for preparing a two-dimensional antiferromagnetic material according to claim 1, characterized in that: In step 3, the mass ratio of In, MnTe and KCl is 1:(3-6):(20-40).

6. The method for preparing a two-dimensional antiferromagnetic material according to claim 1, characterized in that: In step 3, the blocky MnTe precursor and the flux KCl are both ground into powder of 200-3000 mesh; the In powder has a particle size of ≥200 mesh and a purity of ≥99.9%.

7. The method for preparing a two-dimensional antiferromagnetic material according to claim 1, characterized in that: In step 4, the vertical confinement space of constant normal pressure constraint is applied by two stacked high-temperature resistant stainless steel circular plates. Mixed powder II covered by two fluorine crystal mica substrates is placed between the two circular plates. The two circular plates are uniformly pressurized by four pairs of bolts and nuts, with each pair of bolts and nuts applying a torque of 3.0-3.5 N·m.

8. The method for preparing a two-dimensional antiferromagnetic material according to claim 1, characterized in that, In step 4, the fluxing reaction process for preparing two-dimensional Mn(InTe2)2 crystals with fluorinated mica as a substrate is as follows: under an argon atmosphere, the temperature is increased from room temperature to 800-900℃ at a rate of 10-20℃ / min, held for 10-20min, and then naturally cooled to room temperature; the argon gas flow rate is 100-300sccm.

9. The two-dimensional antiferromagnetic material prepared by the preparation method according to any one of claims 1-8, characterized in that: The two-dimensional antiferromagnetic material is a nanoscale few-layer two-dimensional nanosheet structure with a thickness of 10-50 nm; the chemical formula of the two-dimensional antiferromagnetic material is Mn(InTe2)2, with lattice constants a = b = 6.31 Å and c = 12.55 Å, belonging to the tetragonal crystal system. Space group.

10. The application of the two-dimensional antiferromagnetic material prepared by the preparation method according to any one of claims 1-8 in high-density magnetic storage devices.

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