A method for preparing a M-type barium ferrite single crystal thin film under low temperature conditions

Abstract

The application belongs to the technical field of electronic information materials, and specifically provides a method for preparing M-type barium ferrite monocrystal thin film under low temperature conditions; the method is characterized by innovative design of liquid phase raw materials and strict design of liquid phase epitaxy process parameters, and can grow the M-type barium ferrite monocrystal thin film with excellent performance on SGGG (111) substrate by liquid phase epitaxy method under low temperature conditions of 830-850 DEG C, which is not only simple in process and low in cost, but also has high crystallization quality, no impurities and defects. The M-type barium ferrite monocrystal thin film prepared by the method is a single crystal material, the film thickness is up to 150 mu m, the saturation magnetization is about 4500 Oe, the remanence is about 1000 Oe, the easy magnetization axis (c axis) is perpendicular to the film surface, has high uniaxial magnetic crystal anisotropy field, and is very beneficial to realize self-bias design of the device.

Description

Technical Field

[0001] This invention belongs to the field of electronic information materials technology, specifically providing a method for preparing M-type barium ferrite single crystal thin films under low-temperature conditions using liquid phase epitaxy. Background Technology

[0002] As microwave communication technology continues to develop, the requirements for microwave information processing devices are becoming increasingly stringent. Specifically, the demands for device quantity, overall quality, and functional diversity are growing. Since the excellent performance of all electronic devices is built upon superior material properties, microwave materials must possess a series of superior characteristics to continuously improve the performance of microwave information processing devices and accelerate the development and upgrading of microwave communication technology. These characteristics include: planar shape for easy integration and miniaturization; non-reciprocal nature for unidirectional transmission without reverse interference; self-biasing for reduced device size; low loss and ease of operation for lower operating costs.

[0003] As a component in next-generation microwave devices such as circulators, isolators, phase shifters, and filters, M-type barium ferrite (BaFe) 12 O 19 Barium ferrite (BaM) single-crystal thin films belong to the hexagonal crystal system and have very high crystal asymmetry. Their easy magnetization axis (c-axis) perpendicular to the hexagonal crystal axis is very long, resulting in a very strong magnetic anisotropy field, high saturation magnetization, and relatively stable magnetic properties, making them an excellent permanent magnet material. In particular, their high internal uniaxial magnetocrystalline anisotropy field makes them highly suitable for the "self-biased" design of microwave devices, and they are expected to become one of the most influential materials in next-generation microwave and millimeter-wave magnetic devices and microwave integrated circuits. Therefore, the fabrication of M-type barium ferrite single-crystal thin films with high saturation magnetization, high magnetocrystalline anisotropy, high coercivity, high remanence, high easy magnetization axis orientation, and ease of integration into semiconductor devices has become a research focus. Many researchers have devoted themselves to the study of this crystal and proposed many valuable fabrication methods.

[0004] Currently, the main methods for preparing M-type barium ferrite single-crystal thin films include pulsed laser deposition (PLD), radio frequency magnetron sputtering (MS-RF), liquid phase epitaxy (LPE), and screen printing (SP). Among these, pulsed laser deposition is the most studied method. Pulsed laser deposition is a physical vapor deposition technique, where the deposition process involves physical changes without altering the chemical composition of the material. Pulsed laser deposition does not have strict requirements on the substrate, allowing the growth of heterogeneous thin films on substrates with significant differences in crystal structure. Therefore, M-type barium ferrite can be deposited on various substrates, such as Al2O3(0001) and Al2O3(1100), MgO(111), and SiC. However, pulsed laser deposition is difficult to grow thick films, and the high-energy laser beam can easily generate uneven particles or clusters when bombarding the target surface, resulting in non-uniformity of the deposited film and affecting its performance. Furthermore, because plasma expands in a directional region, it cannot deposit large-sized films. In comparison, liquid phase epitaxy (LPE) is one of the most commonly used methods for preparing large-size single-crystal thick ferrite films. It can produce single-crystal thin films with high crystallinity, smooth surfaces, and accurate stoichiometry, making it an important process for manufacturing magnetic single-crystal thin film materials. However, the requirements for substrate materials are very stringent when using LPE to prepare M-type barium ferrites. Not only do the lattice constant and coefficient of thermal expansion of the substrate material need to be close to those of the M-type barium ferrite material, but also, due to the high melting and growth temperatures of the raw materials for preparing M-type barium ferrites, the substrate material needs to have a certain degree of high-temperature resistance and mechanical hardness. Otherwise, the substrate material may melt and break during high-temperature growth, leading to growth failure. For example, the literature “Journal of Applied Physics.1978,49(3):1578-1581;IEEE Transactions on Magnetics.1977,13(5):1241-1243” discloses the direct epitaxial growth of M-type barium ferrite single crystal thin films on non-magnetic spinel substrates (ZnGa2O4 and Mg(In,Ga)2O4). The grown films have high crystal quality, small defects, and reduced ferromagnetic resonance linewidth. However, the substrates used need to be prepared by processes such as melting, which makes the entire film preparation process more complicated and the preparation cost more expensive, and it is not feasible to prepare films in large quantities.For example, the literature “Journal of Applied Physics.2003,93(10):8597-8599;Applied Physics Letters.2008,93(17);Journal of Applied Physics.2002,92(11):6728-6732” discloses the growth of M-type barium ferrite single crystals on Al2O3 and MgO substrates. However, this method requires first depositing an M-type barium ferrite seed layer on the above substrates using pulsed laser deposition technology, and then using this as a seed crystal for liquid phase epitaxial growth. This makes the preparation method cumbersome, the preparation process complex, the preparation cycle long, and the production cost very high, which is also not conducive to the large-scale production of M-type barium ferrite materials.

[0005] Based on this, the present invention provides a method for preparing M-type barium ferrite single crystal thin films under low-temperature conditions using liquid phase epitaxy, thereby directly growing high-quality M-type barium ferrite single crystal thin film materials on a substrate material using liquid phase epitaxy. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing M-type barium ferrite single crystal thin films under low-temperature conditions. Through innovative design of liquid phase raw materials and strict design of liquid phase epitaxy process parameters, this invention utilizes liquid phase epitaxy to directly grow high-performance M-type barium ferrite single crystal thin films on SGGG(111) substrates. This method is not only simple and low-cost, but also produces single crystal thin films with high crystal quality and free from impurities and defects.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A method for preparing M-type barium ferrite single-crystal thin films under low-temperature conditions, characterized by comprising the following steps:

[0009] Step 1. Using Fe2O3, BaCO3, B2O3, and Bi2O3 as raw materials, prepare the mixture according to the molar ratio of Fe2O3:BaCO3:B2O3:Bi2O3 = 46.28:7.74:39.78:6.20;

[0010] Step 2: Transfer the prepared raw materials to a platinum crucible and place the platinum crucible in an ultra-high temperature liquid phase epitaxial furnace for heating and melting to obtain a liquid phase melt; the heating and melting process is as follows: heat at a rate of 2-4℃ / min until 1000℃, and then hold at that temperature for 1-3 hours.

[0011] Step 3: Homogenize the liquid melt using a platinum stirring head;

[0012] Step 4: Set the growth temperature to 830-850℃, reduce the crucible temperature from 1000℃ to the growth temperature at a rate of 2-4℃ / min, then place the substrate material in the crucible and completely immerse the substrate material in the liquid melt. Keep the substrate rotating at a speed of 10-40r / min for 10-20h to allow the M-type barium ferrite single crystal material to be deposited and grown on the substrate material.

[0013] Step 5: Extract the substrate with M-type barium ferrite single crystal material grown into liquid melt at a speed of 5-8 mm / min (the extraction speed should not be too fast, otherwise the substrate material will break), and keep it in the furnace to cool with the furnace. Remove it after cooling to room temperature.

[0014] Step 6: Clean the removed M-type barium ferrite single crystal material to remove molten impurities from the surface and obtain an M-type barium ferrite single crystal thin film.

[0015] Furthermore, in step 1, the ingredient preparation process is as follows: weigh the raw materials separately, with the mass error of all raw materials not exceeding ±0.2g; mix all raw materials and mechanically stir for 10-20 minutes, then grind for 30-60 minutes; all utensils are cleaned with 99.9% alcohol during the ingredient preparation process, and the ingredient preparation process is carried out in a dust-free environment.

[0016] Furthermore, in step 1, the purity of all raw materials is 99.999%.

[0017] Furthermore, in step 3, the homogenization process is as follows: the platinum stirring head is lowered below the liquid melt surface and stirred at a speed of 30-50 r / min, switching between forward and reverse directions every 1-2 minutes for 5-6 hours.

[0018] Furthermore, in step 4, the substrate material is placed 10-15 cm below the surface of the liquid melt.

[0019] Furthermore, in step 4, the substrate material is an SGGG(111) substrate with a length of 15 mm, a width of 10 mm, and a thickness of 500 μm.

[0020] Further, in step 6, the cleaning process is as follows: First, using an ultrasonic cleaner, the M-type barium ferrite single crystal material is ultrasonically cleaned sequentially with 99.9% alcohol, acetone, and then 99.9% alcohol, with each ultrasonic cleaning lasting 30–40 minutes; then, the M-type barium ferrite single crystal material is placed in a mixed solvent of concentrated nitric acid and deionized water, and heated to 180–200°C on a heating stage and held at that temperature for 30–60 minutes; finally, ultrasonic cleaning is performed multiple times with deionized water to thoroughly remove residual impurities from the material surface, with each ultrasonic cleaning lasting 20–30 minutes; the volume ratio of concentrated nitric acid to deionized water in the mixed solvent is 1:1.

[0021] Based on the above technical solution, the beneficial effects of the present invention are as follows:

[0022] This invention provides a method for preparing M-type barium ferrite single-crystal thin films under low-temperature conditions. First, the liquid phase raw materials are creatively designed, and the proportions between the raw materials are rigorously explored. Finally, a raw material formula suitable for the growth of M-type barium ferrite single-crystal materials is designed. Most importantly, B2O3 and Bi2O3 are used as fluxes to reduce the overall melting point and viscosity of the raw materials, allowing the growth temperature of the material to be at a lower level. This solves the problem of high-temperature growth being detrimental to the substrate and realizes the preparation of high-quality M-type barium ferrite single-crystal thin films. Then, the liquid phase epitaxial process parameters are rigorously designed, and a relatively slow heating and cooling method is adopted to ensure that the thin film material does not break due to stress. Finally, high-performance M-type barium ferrite single-crystal thin films are directly grown on SGGG(111) substrates using liquid phase epitaxy at low-temperature conditions of 830-850℃. This method is not only simple and low-cost, but also produces single-crystal thin films with high crystal quality and no impurities or defects. The M-type barium ferrite single-crystal thin film prepared by this invention is a single-crystal material with a thickness of up to 150 μm, a saturation magnetization of about 4500 Oe, a remanence of about 1000 Oe, and an easy magnetization axis (c-axis) perpendicular to the film surface orientation. It has a high uniaxial magnetocrystalline anisotropy field, which is very beneficial for realizing the self-biased design of the device. Attached Figure Description

[0023] Figure 1 This is a process flow diagram of the method for preparing M-type barium ferrite single crystal thin films under low-temperature conditions using liquid phase epitaxy in this invention.

[0024] Figure 2 The image shows the XRD pattern of the M-type barium ferrite single crystal thin film prepared in Example 1 of this invention.

[0025] Figure 3 This is a hysteresis loop diagram of the M-type barium ferrite single crystal thin film prepared in Example 1 of the present invention.

[0026] Figure 4 This is a physical image of the M-type barium ferrite single crystal thin film with the substrate removed in Embodiment 1 of the present invention. Detailed Implementation

[0027] To make the objectives, technical solutions, and effective effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0028] Example 1

[0029] This embodiment provides a method for preparing M-type barium ferrite single-crystal thin films at low temperatures using liquid-phase epitaxy. Specifically, the M-type barium ferrite single-crystal thin film material is grown at a constant temperature of 830°C, and the process is as follows: Figure 1 As shown, the specific steps are as follows:

[0030] Step 1: Weigh the following raw materials using a high-precision balance: Fe2O3 (1011.92g), BaCO3 (208.44g), B2O3 (379.32g), and Bi2O3 (400.30g). The mass error of all raw materials shall not exceed ±0.2g, and the purity of all raw materials shall be 99.999%. Before weighing the raw materials, all beakers and glasswares shall be wiped with 99.9% alcohol to ensure the cleanliness of the surface and interior of the utensils used. The entire weighing process shall be carried out in a clean room.

[0031] Step 2: Transfer the prepared raw materials to a 3-inch high-purity platinum crucible and place the crucible filled with raw materials into an ultra-high temperature liquid phase epitaxial furnace for heating and melting. Before transferring the raw materials to the platinum crucible, use a glass stirring rod to perform preliminary mechanical stirring to ensure that the raw materials are roughly uniformly mixed, and then grind for 30-60 minutes. During the raw material transfer process, press the materials multiple times with a spatula after transferring a certain amount of raw materials to ensure that all raw materials can be transferred into the crucible at one time. After the raw materials are completely transferred, place the platinum crucible into the liquid phase epitaxial furnace and heat it at a rate of 4℃ / min. When the temperature reaches 800℃, the raw materials begin to melt. Further heating to a temperature greater than 1000℃ will completely melt the raw materials. Then hold the temperature for 1-3 hours.

[0032] Step 3: Install a stirring head on the liquid phase epitaxial furnace body and lower it below the liquid phase raw material surface. Stir the liquid phase melt at a speed of 30 r / min, and stir in both directions once every 1 minute until the melt is stirred evenly.

[0033] Step 4: Reduce the crucible temperature from 1000℃ to 830℃ at a rate of 2℃ / min. Then remove the stirring head, attach the substrate fixture, and fix the SGGG substrate with a length × width of 10 × 15 mm and a thickness of 500 μm on the substrate fixture. Then slowly lower the substrate material to a position about 10 cm below the liquid melt surface and slowly rotate the substrate at a speed of 10 r / min. Subsequently, the M-type barium ferrite single crystal material will gradually deposit and grow on the SGGG substrate.

[0034] Step 5: After growing for about 10 to 20 hours, the M-type barium ferrite single crystal material is deposited on the SGGG substrate and forms a certain thickness. The substrate material is slowly removed from the liquid melt at a rotation speed of 5 mm / min. The removal speed should not be too fast, otherwise the substrate material will break. Then the substrate material is left in the furnace to cool with the furnace. After cooling to room temperature, the single crystal material is removed.

[0035] Step 6: Using an ultrasonic cleaner, the freshly removed single crystal material is initially cleaned for 30 minutes in the order of 99.9% alcohol, acetone, and 99.9% alcohol. Then, the single crystal material is placed in a mixed solvent of concentrated nitric acid and deionized water with a volume ratio of 1:1, and heated to 200°C on a heating table for 60 minutes. Finally, it is ultrasonically cleaned multiple times with deionized water to thoroughly remove the residual impurities on the material surface.

[0036] Example 2

[0037] This embodiment describes the growth of M-type barium ferrite single-crystal thin film material at a constant temperature of 840℃. The specific steps are as follows:

[0038] Step 1: Weigh the following raw materials using a high-precision balance: Fe2O3 (1011.92g), BaCO3 (208.44g), B2O3 (379.32g), and Bi2O3 (400.30g). The mass error of all raw materials shall not exceed ±0.2g, and the purity of all raw materials shall be 99.999%. Before weighing the raw materials, all beakers and glasswares shall be wiped with 99.9% alcohol to ensure the cleanliness of the surface and interior of the utensils used. The entire weighing process shall be carried out in a clean room.

[0039] Step 2: Transfer the prepared raw materials to a 3-inch high-purity platinum crucible and place the crucible filled with raw materials into an ultra-high temperature liquid phase epitaxy furnace for heating and melting. Before transferring the raw materials to the platinum crucible, use a glass stirring rod to perform preliminary mechanical stirring to ensure that the raw materials are roughly uniformly mixed, and then grind for 30-60 minutes. During the raw material transfer process, press the raw materials multiple times with a spatula after each transfer to ensure that the entire raw material is completely compacted and that all the raw materials can be transferred into the crucible at one time. After the raw materials are completely transferred, place the platinum crucible into the liquid phase epitaxy furnace and heat it at a rate of 4℃ / min. When the temperature reaches 800℃, the raw materials begin to melt. Further heating to a temperature greater than 1000℃ will completely melt the raw materials. Then hold the temperature for 1-3 hours.

[0040] Step 3: Install a stirring head on the liquid phase epitaxial furnace body and lower it below the liquid phase raw material surface. Stir the liquid phase melt at a speed of 30 r / min, and stir in both directions once every 1 minute until the melt is stirred evenly.

[0041] Step 4: Reduce the crucible temperature from 1000℃ to 840℃ at a rate of 2℃ / min. Then remove the stirring head, attach the substrate fixture, and fix the SGGG substrate with a length × width of 10 × 15 mm and a thickness of 500 μm on the substrate fixture. Then slowly lower the substrate material to a position about 10 cm below the liquid melt surface and slowly rotate the substrate at a speed of 10 r / min. Subsequently, the M-type barium ferrite single crystal material will gradually deposit and grow on the SGGG substrate.

[0042] Step 5: After growing for about 10 to 20 hours, the M-type barium ferrite single crystal material is deposited on the SGGG substrate and forms a certain thickness. The substrate material is slowly removed from the liquid melt at a rotation speed of 5 mm / min. The removal speed should not be too fast, otherwise the substrate material will break. Then the substrate material is left in the furnace to cool with the furnace. After cooling to room temperature, the single crystal material is removed.

[0043] Step 6: Using an ultrasonic cleaner, the freshly removed single crystal material is initially cleaned for 30 minutes in the order of 99.9% alcohol, acetone, and 99.9% alcohol. Then, the single crystal material is placed in a mixed solvent of concentrated nitric acid and deionized water with a volume ratio of 1:1, and heated to 200°C on a heating table for 60 minutes. Finally, it is ultrasonically cleaned multiple times with deionized water to thoroughly remove the residual impurities on the material surface.

[0044] Example 3

[0045] This embodiment describes the growth of M-type barium ferrite single-crystal thin film material at a constant temperature of 850℃. The specific steps are as follows:

[0046] Step 1: Weigh the following raw materials using a high-precision balance: Fe2O3 (1011.92g), BaCO3 (208.44g), B2O3 (379.32g), and Bi2O3 (400.30g). The mass error of all raw materials shall not exceed ±0.2g, and the purity of all raw materials shall be 99.999%. Before weighing the raw materials, all beakers and glasswares shall be wiped with 99.9% alcohol to ensure the cleanliness of the surface and interior of the utensils used. The entire weighing process shall be carried out in a clean room.

[0047] Step 2: Transfer the prepared raw materials to a 3-inch high-purity platinum crucible and place the crucible filled with raw materials into an ultra-high temperature liquid phase epitaxy furnace for heating and melting. Before transferring the raw materials to the platinum crucible, use a glass stirring rod to perform preliminary mechanical stirring to ensure that the raw materials are roughly uniformly mixed, and then grind for 30-60 minutes. During the raw material transfer process, press the raw materials multiple times with a spatula after each transfer to ensure that the entire raw material is completely compacted and that all the raw materials can be transferred into the crucible at one time. After the raw materials are completely transferred, place the platinum crucible into the liquid phase epitaxy furnace and heat it at a rate of 4℃ / min. When the temperature reaches 800℃, the raw materials begin to melt. Further heating to a temperature greater than 1000℃ will completely melt the raw materials. Then hold the temperature for 1-3 hours.

[0048] Step 3: Install a stirring head on the liquid phase epitaxial furnace body and lower it below the liquid phase raw material surface. Stir the liquid phase melt at a speed of 30 r / min, and stir in both directions once every 1 minute until the melt is stirred evenly.

[0049] Step 4: Reduce the crucible temperature from 1000℃ to 850℃ at a rate of 2℃ / min. Then remove the stirring head, attach the substrate fixture, and fix the SGGG substrate with a length × width of 10 × 15 mm and a thickness of 500 μm on the substrate fixture. Then slowly lower the substrate material to a position about 10 cm below the liquid melt surface and slowly rotate the substrate at a speed of 10 r / min. Subsequently, the M-type barium ferrite single crystal material will gradually deposit and grow on the SGGG substrate.

[0050] Step 5: After growing for about 10 to 20 hours, the M-type barium ferrite single crystal material is deposited on the SGGG substrate and forms a certain thickness. The substrate material is slowly removed from the liquid melt at a rotation speed of 5 mm / min. The removal speed should not be too fast, otherwise the substrate material will break. Then the substrate material is left in the furnace to cool with the furnace. After cooling to room temperature, the single crystal material is removed.

[0051] Step 6: Using an ultrasonic cleaner, the freshly removed single crystal material is initially cleaned for 30 minutes in the order of 99.9% alcohol, acetone, and 99.9% alcohol. Then, the single crystal material is placed in a mixed solvent of concentrated nitric acid and deionized water with a volume ratio of 1:1, and heated to 200°C on a heating table for 60 minutes. Finally, it is ultrasonically cleaned multiple times with deionized water to thoroughly remove the residual impurities on the material surface.

[0052] The M-type hexagonal ferrite single-crystal thin film materials prepared in Examples 1-3 above were tested, and their performance indicators are shown in the table below:

[0053] Example <![CDATA[4πM s (You)]]> <![CDATA[4πM r (You)]]> <![CDATA[H c (You)]]> 1 4510 994 90 2 4503 1108 98 3 4420 1014 96

[0054] As can be seen from the table, the M-type barium ferrite thin film prepared by the present invention has high saturation magnetization and good remanence, and can be applied to microwave / millimeter-wave devices. At the same time, the low coercivity indicates that there is less pinning effect caused by defects and grain boundaries in the material, the thin film has high crystal quality, and the microwave loss in actual use will be lower.

[0055] Meanwhile, the XRD pattern of the M-type hexagonal ferrite single crystal thin film material prepared in Example 1 is as follows: Figure 2 As shown, the hysteresis loop diagram is as follows: Figure 3 As shown, the physical image without the substrate is as follows. Figure 4 As shown in the figure, the M-type barium ferrite thin film prepared by the present invention has a highly vertical orientation of the easily magnetized c-axis. The prepared thin film has high structural and performance anisotropy and can be applied to high-field devices.

[0056] The above description is merely a specific embodiment of the present invention. Any feature disclosed in this specification may be replaced by other equivalent or similar features unless otherwise specified. All disclosed features, or steps in all methods or processes, may be combined in any way except for mutually exclusive features and / or steps.

Claims

1. A method for preparing M-type barium ferrite single-crystal thin films under low-temperature conditions, characterized in that, Includes the following steps: Step 1. Using Fe2O3, BaCO3, B2O3, and Bi2O3 as raw materials, prepare the mixture according to the molar ratio of Fe2O3:BaCO3:B2O3:Bi2O3 = 46.28:7.74:39.78:6.20; Step 2: Transfer the prepared raw materials to a platinum crucible and place the platinum crucible in an ultra-high temperature liquid phase epitaxial furnace for heating and melting to obtain a liquid phase melt; the heating and melting process is as follows: heat at a rate of 4~6℃ / min until 1000℃, and then hold at that temperature for 1~3 h. Step 3: Homogenize the liquid melt using a platinum stirring head; Step 4: Set the growth temperature to 830~850℃, reduce the crucible temperature from 1000℃ to the growth temperature at a rate of 2~4℃ / min, then put in the substrate material and completely immerse the substrate material in the liquid melt. Keep the substrate rotating at a speed of 10~40r / min for 10~20 h to allow the M-type barium ferrite single crystal material to be deposited and grown on the substrate material. The substrate material is SGGG(111) substrate. Step 5: Extract the liquid melt from the substrate on which the M-type barium ferrite single crystal material has grown at a speed of 5~8 mm / min, and keep it in the furnace to cool with the furnace. Remove it after cooling to room temperature. Step 6: Clean the removed M-type barium ferrite single crystal material to remove molten impurities from the material surface and obtain an M-type barium ferrite single crystal thin film.

2. The method for preparing M-type barium ferrite single crystal thin films under low-temperature conditions according to claim 1, characterized in that, In step 1, the ingredient preparation process is as follows: weigh the raw materials separately, and the mass error of all raw materials shall not exceed ±0.2 g; mix all raw materials and mechanically stir for 10~20 min, and then grind for 30~60 min; all utensils are cleaned with 99.9% alcohol during the ingredient preparation process, and the ingredient preparation process is carried out in a dust-free environment.

3. The method for preparing M-type barium ferrite single crystal thin films under low-temperature conditions according to claim 1, characterized in that, In step 1, the purity of all raw materials is 99.999%.

4. The method for preparing M-type barium ferrite single crystal thin films under low-temperature conditions according to claim 1, characterized in that, In step 3, the homogenization process is as follows: the platinum stirring head is lowered below the liquid melt surface and stirred at a speed of 30~50 r / min, switching the forward and reverse directions every 1~2 minutes for 5~6 hours.

5. The method for preparing M-type barium ferrite single crystal thin films under low-temperature conditions according to claim 1, characterized in that, In step 4, the substrate material is placed 10-15 cm below the liquid surface of the liquid phase melt.

6. The method for preparing M-type barium ferrite single crystal thin films under low-temperature conditions according to claim 1, characterized in that, In step 4, the substrate material has a length of 15 mm, a width of 10 mm, and a thickness of 500 μm.

7. The method for preparing M-type barium ferrite single crystal thin films under low-temperature conditions according to claim 1, characterized in that, In step 6, the cleaning process is as follows: First, using an ultrasonic cleaner, the M-type barium ferrite single crystal material is ultrasonically cleaned in the order of 99.9% alcohol, acetone, and 99.9% alcohol, with each ultrasonic cleaning lasting 30-40 minutes; then, the M-type barium ferrite single crystal material is placed in a mixed solvent of concentrated nitric acid and deionized water, and heated to 180-200 ℃ on a heating stage and kept at that temperature for 30-60 minutes, with the volume ratio of concentrated nitric acid and deionized water in the mixed solvent being 1:1; finally, ultrasonic cleaning is performed multiple times using deionized water, with each ultrasonic cleaning lasting 20-30 minutes.

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