A double-sided garnet single crystal film for magneto-optical detection and a preparation method and application thereof

Abstract

The application provides a kind of for magneto-optical detection double-sided garnet single crystal film and its preparation method and application.The preparation method comprises the following steps: using Ga2O3, Tm2O3, Fe2O3, Bi2O3 as raw materials, then adding K2CO3, mixing, melting, to obtain a homogeneous melt;cleaning the substrate;the cleaned substrate is put into the melt, at a temperature of 850-920°C, the substrate rotation speed is 50-110rpm / min, the growth time is 5-15min, after the growth is completed, cleaning, to obtain a kind of for magneto-optical detection double-sided garnet single crystal film according to the application.The application adopts liquid phase epitaxy process, realizes the growth of high-quality thin film, prepares a kind of double-sided single crystal garnet magneto-optical thin film which can be used for magneto-optical detection, the preparation process is simple, the stability is high, and industrial production can be realized.

Description

Technical Field

[0001] This invention relates to the field of garnet single crystal thin film technology, specifically to a double-sided garnet single crystal thin film for magneto-optical detection, its preparation method, and its application. Background Technology

[0002] Magneto-optical testing is primarily based on the Faraday magneto-optical effect. When a beam of linearly polarized light passes through a magneto-optical sensor placed on the surface of a sample, if a leakage magnetic field exists, the polarization direction of the linearly polarized light will rotate by a certain angle, which is proportional to the strength of the leakage magnetic field. This effect enables magneto-optical testing to detect internal defects in materials. With the development of modern industry, magneto-optical testing, as a visual non-destructive testing technology, has advantages such as high detection efficiency, high accuracy, and ease of use. It can achieve real-time visual detection of small surface and subsurface defects, and the results are intuitive, easy to understand, and easy to store. Currently, magneto-optical testing technology has developed into a comprehensive testing technology integrating optical imaging, circuit design, image capture and storage, and image processing. In the future, with continuous technological advancements and expanding applications, magneto-optical testing technology will usher in even broader development prospects.

[0003] As device sizes continue to shrink and integration levels increase, higher demands are placed on magneto-optical imaging crystal materials. On one hand, materials are required to be thin-film and of high quality; on the other hand, they need to possess excellent properties, such as magneto-optical performance, thermal stability, and mechanical properties, to withstand complex environments such as high temperatures and high vacuum. Furthermore, it is necessary to develop magneto-optical imaging crystal material fabrication technologies suitable for large-scale production to reduce costs and improve production efficiency. However, the growth methods for magneto-optical crystals are complex, and growing large-size, high-quality magneto-optical crystals is extremely difficult, prone to defects and poor uniformity, affecting wafer performance and yield. How to obtain large-size, high-quality magneto-optical crystals through effective growth methods is currently one of the key challenges. Summary of the Invention

[0004] This invention addresses the problems of complex growth methods, susceptibility to defects, and poor uniformity in magneto-optical crystals. It proposes a method for preparing double-sided garnet single-crystal thin films for magneto-optical detection, along with its application. By adding a certain amount of alkali metal, this invention utilizes liquid-phase epitaxy to grow Tm, Bi, and Ga co-doped garnet single-crystal thin films on gadolinium gallium garnet (GGG) substrates, resulting in large-size, high-quality magneto-optical detection wafers.

[0005] The technical solution adopted in this invention is as follows:

[0006] A method for preparing double-sided garnet single-crystal thin films for magneto-optical detection includes the following steps:

[0007] Step 1: Melt preparation: Using Ga2O3, Tm2O3, Fe2O3, and Bi2O3 as raw materials, K2CO3 is added, and the mixture is stirred and melted to obtain a homogeneous melt. Bi2O3 serves as both a component and a flux for the thin film, while K2CO3 reduces the surface tension of the melt. The specific gravity of Ga2O3, Tm2O3, Fe2O3, and Bi2O3 is (0.5%–1%), (1%–2%), (5%–6%), and (85%–95%), respectively, and the weight of K2CO3 is 0.5%–1.0% of the total weight.

[0008] Step 2: Clean the substrate;

[0009] Step 3: Liquid phase epitaxy to grow thin film: Place the substrate cleaned in step 2 into the melt, grow at a temperature of 850-920°C, a substrate rotation speed of 50-110 rpm / min, for a growth time of 5-15 min. After growth, clean the substrate to obtain the double-sided garnet single crystal thin film for magneto-optical detection described in this invention.

[0010] Further, in step 1, the mixing step includes: mixing Ga2O3, Tm2O3, Fe2O3, Bi2O3, and K2CO3.

[0011] Further, one-third of the mixed raw materials are placed in a crucible and melted at 1040–1050°C for 8–12 hours, held at that temperature for 2–5 hours, and then cooled to below 100°C. Then, one-third of the mixed raw materials are placed in a crucible and melted at 1040–1050°C for 8–12 hours, held at that temperature for 2–5 hours, and then cooled to below 100°C. Finally, one-third of the mixed raw materials are placed in a crucible and melted at 1040–1050°C for 8–12 hours, held at that temperature for 8–12 hours, and stirred at 1040–1050°C for 8–12 hours to obtain a uniformly mixed melt.

[0012] Furthermore, the substrate described in step 2 is a gadolinium gallium garnet (GGG) substrate. The substrate cleaning process includes: Step 1, cleaning with trichloroethylene at 60-90℃ for 5-10 minutes, then cleaning with deionized water at 60-90℃ for 5-10 minutes; Step 2, immersing the substrate treated in Step 1 in a mixed solution of potassium dichromate, concentrated sulfuric acid, and water at 60-90℃ 10-15 times, with each immersion time being 1-3 seconds; Step 3, cleaning the substrate treated in Step 2 twice with deionized water at 60-90℃, with each cleaning time being 5-10 minutes; Step 4, immersing the substrate treated in Step 3 in a mixed solution of sodium carbonate, sodium phosphate, and potassium hydroxide at 60-90℃ for 3-5 minutes; Step 5, immersing the substrate treated in Step 4 sequentially in deionized water at 60-90℃, ammonia solution, and deionized water at room temperature for 5-10 minutes each; Step 6, cleaning the substrate treated in Step 5 under isopropanol vapor condensation and reflux conditions for 5-10 minutes. In step 2, the mass concentration of potassium dichromate in the mixed solution is 15–20 g / L, and the molar concentration of concentrated sulfuric acid is 10–15 mol / L. In step 4, the mass ratio of sodium carbonate, sodium phosphate, and potassium hydroxide in the mixed solution is 0.5–1:1:1. In step 5, the volume percentage of ammonia solution is 25%–35%.

[0013] Further, in step 3, the angle between the substrate and the melt plane is 10-30°. After growth is completed, the substrate is quickly lifted to 20 mm from the melt surface and the process is stopped, allowing the substrate to cool down naturally with the furnace. After cooling to room temperature, the substrate is slowly removed from the furnace. Finally, the obtained substrate with the thin film is cleaned in a mixed solution of nitric acid and water for 30-45 min. The volume ratio of nitric acid to water is 0.5-1:1.

[0014] This invention also provides a magneto-optical detection double-sided garnet single-crystal thin film, which is prepared by the above-described preparation method. The chemical formula of the single-crystal thin film is (Bi... x Tm 3-x (Ga) y Fe 5-y )O 12 , of which 0 <x<3,0<y<5。

[0015] The present invention also provides an application of double-sided garnet single crystal thin film for magneto-optical detection in magneto-optical detection devices.

[0016] The beneficial effects of this invention are as follows:

[0017] 1. The advantages of this invention include: First, by employing liquid-phase epitaxy, the doping amounts of Bi, Tm, and Ga ions are calculated through matching degree to achieve maximum lattice matching, thereby obtaining a high-quality thin film; Second, K₂CO₃ is used as an additive in this invention to reduce the surface tension of the melt, thus obtaining a high-quality thin film. In summary, this invention uses liquid-phase epitaxy to achieve the growth of a high-quality thin film, preparing a double-sided single-crystal garnet magneto-optical thin film that can be used for magneto-optical detection. The preparation process is simple, highly stable, and can be industrialized.

[0018] 2. The present invention adjusts the wetting angle between the melt and the substrate, so that the melt can easily flow down from the substrate surface after growth, thereby improving the film quality.

[0019] 3. The Bi:TmIG double-sided thin film prepared by this invention has a total thickness of 16-21 μm, no melt residue on its surface, excellent mirror effect, and good stability. Attached Figure Description

[0020] Figure 1 A schematic diagram of the liquid phase epitaxial furnace used in the preparation of magneto-optical detection double-sided garnet single crystal thin films provided by the present invention;

[0021] Figure 2 A graph showing the relationship between growth temperature and growth rate during the preparation of garnet single-crystal thin films by liquid-phase epitaxy provided by the present invention.

[0022] Figure 3 This is a photograph of the garnet single-crystal thin film prepared in Example 1 of the present invention.

[0023] Figure 4 An optical microscope image of the garnet single-crystal thin film prepared in Example 1 of this invention;

[0024] Figure 5 This is a photograph of the garnet single-crystal thin film prepared in Example 2 of the present invention.

[0025] Figure 6 This is an optical microscope image of the garnet single-crystal thin film prepared in Example 2 of the present invention.

[0026] Figure label:

[0027] 1-Support, 2-Rotating frame, 3-Furnace body, 4-Platinum crucible, 5-Melted material, 6-Motor, 7-Ceramic lifting rod. Detailed Implementation

[0028] The technical solution of the present invention will be described in detail below with reference to specific embodiments. The following embodiments are only used to illustrate the technical solution of the present invention in more detail, and are therefore only examples, and should not be used to limit the scope of protection of the present invention.

[0029] This invention provides a method for preparing double-sided garnet single-crystal thin films for magneto-optical detection, comprising the following steps:

[0030] Step 1: Weighing raw materials: Using Ga2O3, Tm2O3, Fe2O3, and Bi2O3 as raw materials, add K2CO3, mix and melt to obtain a uniformly mixed melt.

[0031] In one embodiment, the specific gravity of Ga2O3, Tm2O3, Fe2O3, and Bi2O3 is (0.5%–1%), (1%–2%), (5%–6%), and (85%–95%), respectively, and the weight of K2CO3 is 0.5% of the total weight. For example, the specific gravity of Ga2O3, Tm2O3, Fe2O3, and Bi2O3 is 0.7%, 1.3%, 5.5%, and 92.5%, respectively.

[0032] In one embodiment, Bi2O3 serves as both a component and a flux for the thin film, while K2CO3 reduces the surface tension of the melt.

[0033] In one embodiment, the melting step includes: placing one-third of the mixed raw materials into a crucible, melting at 1040–1050°C for 8–12 hours, holding at that temperature for 2–5 hours, and then cooling to below 100°C; then placing one-third of the mixed raw materials into the crucible, melting at 1040–1050°C for 8–12 hours, holding at that temperature for 2–5 hours, and then cooling to below 100°C; finally placing one-third of the mixed raw materials into the crucible, melting at 1040–1050°C for 8–12 hours, holding at that temperature for 8–12 hours, and stirring at 1040–1050°C for 8–12 hours to obtain a uniformly mixed melt.

[0034] Step 2: Clean the substrate.

[0035] In one embodiment, the substrate is a gadolinium gallium garnet (GGG) substrate. The cleaning process of the substrate includes: Step 1, first clean with trichloroethylene at 60 - 90 °C for 5 - 10 min, and then clean with deionized water at 60 - 90 °C for 5 - 10 min; Step 2, immerse the substrate processed in Step 1 in a mixed solution of potassium dichromate, concentrated sulfuric acid and water at 60 - 90 °C for 10 - 15 times, with each immersion time of 1 - 3 seconds; Step 3, clean the substrate processed in Step 2 twice with deionized water at 60 - 90 °C, with each cleaning time of 5 - 10 min; Step 4, soak the substrate processed in Step 3 in a mixed solution of sodium carbonate, sodium phosphate and potassium hydroxide at 60 - 90 °C for 3 - 5 min; Step 5, successively place the substrate processed in Step 4 in deionized water at 60 - 90 °C, an ammonia water solution with a volume percentage of 25% - 35%, and deionized water at room temperature for cleaning for 5 - 10 min respectively; Step 6, clean the substrate processed in Step 5 for 5 - 10 min under the condition of isopropyl alcohol vapor condensation reflux. Among them, in Step 2, the mass concentration of potassium dichromate in the mixed solution is 15 - 20 g / L, and the molar concentration of concentrated sulfuric acid is 10 - 15 mol / L. Among them, in Step 5, the mass ratio of sodium carbonate, sodium phosphate and potassium hydroxide in the mixed solution is 0.5 - 1:1:1.

[0036] Step 3, growing the thin film by liquid phase epitaxy: Fix the cleaned substrate on a platinum fixture, making the angle between it and the horizontal plane 10 - 30 °, then slowly place the platinum fixture with the substrate into the furnace body, preheat it at 30 mm above the melt surface for 5 - 10 min, and then completely immerse it in the melt. Under the conditions of a growth temperature of 850 - 920 °C and a rotation speed of 50 - 110 rpm / min, the growth time is 5 - 15 min. After the growth is completed, quickly lift the substrate to 20 mm above the melt liquid surface and stop the process, allowing the substrate to cool naturally with the furnace body. After cooling to room temperature, slowly take out the substrate from the furnace body; finally, clean the obtained substrate with the thin film in a mixed solution of nitric acid and water for 30 - 45 min to obtain the double-sided garnet single crystal thin film, and the chemical formula of the thin film is (Bi x Tm 3-x )(Ga y Fe 5-y )O 12 , where 0 < x < 3 and 0 < y < 5. The volume ratio of nitric acid to water is 0.5 - 1:1.

[0037] As Figure 1As shown, the liquid phase epitaxial furnace structure used in the preparation of double-sided garnet single crystal thin films for magneto-optical detection according to the present invention includes: a support 1, a rotating frame 2 connected to the bottom of the support 1, the rotating frame 2 extending into the furnace body 3 to fix a platinum crucible 4, the platinum crucible 4 being used to fill melt 5, a motor 6 mounted on the support 1, the motor 6 being connected to a ceramic lifting rod 7, the ceramic lifting rod 7 extending into the furnace body 3 to stir the melt 5. A heater is installed on the inner wall of the furnace body 3. After raising the furnace body 3, the rotating frame 2 is rotated, and the platinum crucible 4 is placed on the rotating frame 2. The rotating frame 2 is rotated again to lower the furnace body 3, allowing the platinum crucible 4 to be sent into the furnace body 3; the platinum clamp is fixed on the ceramic lifting rod 7, and the ceramic lifting rod 7 is rotated, slowly lowering the ceramic lifting rod 7 to send the platinum clamp into the platinum crucible 4.

[0038] like Figure 2 As shown, the relationship between growth temperature and growth rate is that the growth rate of the film slows down as the growth temperature increases.

[0039] The present invention will be described in detail below through embodiments and experimental examples. However, these are merely examples and do not limit the present invention in any way.

[0040] Example 1

[0041] This invention provides a method for preparing double-sided garnet single-crystal thin films for magneto-optical detection, comprising the following steps:

[0042] Step 1: Weighing raw materials: Using Ga2O3, Tm2O3, Fe2O3, and Bi2O3 as raw materials, weigh the specific gravity of Ga2O3, Tm2O3, Fe2O3, and Bi2O3 to be 0.66%, 1.53%, 5.98%, and 91.83% respectively, and the weight of K2CO3 is 0.5% of the total weight.

[0043] Step 2, Melt Preparation: Place the raw materials weighed in Step 1 into a rolling mill and mix for 12 hours. Take one-third of the mixed raw materials and place them in a crucible. Melt the raw materials at 1045°C for 12 hours, hold for 2 hours, and then cool down to below 100°C. Take another one-third of the mixed raw materials and place them in a crucible. Melt the raw materials at 1045°C for 12 hours, hold for 2 hours, and then cool down to below 100°C. Finally, place the remaining raw materials in a crucible. Melt the raw materials at 1045°C for 12 hours, hold for 12 hours, and stir at 1045°C for 12 hours to obtain a uniformly mixed melt.

[0044] Step 3: Cleaning the substrate: First, clean the gadolinium gallium garnet (GGG) substrate with trichloroethylene at 85°C for 8 minutes, then clean it with deionized water at 85°C for 6 minutes. Immerse the substrate treated in the previous step 10 times in a mixed solution of potassium dichromate, concentrated sulfuric acid, and water at 85°C, with each immersion time being 2 seconds. The mass concentration of potassium dichromate in the mixed solution is 16 g / L, and the molar concentration of concentrated sulfuric acid is 11 mol / L. Then, clean it twice with deionized water at 85°C, with each cleaning time being 6 minutes. Immerse the substrate treated in the previous step in a mixed solution of sodium carbonate, sodium phosphate, and potassium hydroxide at 85°C for 3 minutes. The mass ratio of sodium carbonate, sodium phosphate, and potassium hydroxide in the mixed solution is 1:1:1. Then, immerse the substrate treated in the previous step sequentially in deionized water at 85°C, ammonia solution with a volume percentage of 28%, and deionized water at room temperature for 6 minutes each. Finally, clean the substrate treated in the previous step under isopropanol vapor reflux conditions for 6 minutes.

[0045] Step 4: Liquid phase epitaxy for thin film growth: Fix the substrate cleaned in Step 3 onto a platinum jig with an angle of 20° to the horizontal plane. Then, slowly place the platinum jig with the substrate into the furnace and preheat it for 10 minutes at a height of 30 mm above the melt surface. After that, completely immerse it in the melt and grow it for 10 minutes at a growth temperature of 863°C and a rotation speed of 65 rpm / min. After growth, quickly lift the substrate to a height of 20 mm from the melt surface and stop the process. Allow the substrate to cool naturally with the furnace. After cooling to room temperature, slowly remove the substrate from the epitaxial furnace. Finally, clean the obtained substrate with the thin film in a nitric acid:water mixture of 0.5:1 for 35 minutes to obtain the double-sided garnet single crystal thin film.

[0046] like Figure 3 As shown, Example 1 yielded a double-sided garnet single-crystal thin film with a total film thickness of 16 μm. Figure 4 This indicates that the obtained garnet single crystal thin film has high quality characteristics.

[0047] Example 2

[0048] This invention provides a method for preparing double-sided garnet single-crystal thin films for magneto-optical detection, comprising the following steps:

[0049] Step 1: Weighing raw materials: Using Ga2O3, Tm2O3, Fe2O3, and Bi2O3 as raw materials, weigh the specific gravity of Ga2O3, Tm2O3, Fe2O3, and Bi2O3 to be 0.66%, 1.53%, 5.98%, and 91.83% respectively, and the weight of K2CO3 is 0.5% of the total weight.

[0050] Step 2, Melt Preparation: Place the raw materials weighed in Step 1 into a rolling mill and mix for 12 hours. Take one-third of the mixed raw materials and place them in a crucible. Melt the raw materials at 1045°C for 12 hours, hold for 2 hours, and then cool down to below 100°C. Take another one-third of the mixed raw materials and place them in a crucible. Melt the raw materials at 1045°C for 12 hours, hold for 2 hours, and then cool down to below 100°C. Finally, place the remaining raw materials in a crucible. Melt the raw materials at 1045°C for 12 hours, hold for 12 hours, and stir at 1045°C for 12 hours to obtain a uniformly mixed melt.

[0051] Step 3: Cleaning the substrate: First, clean the gadolinium gallium garnet (GGG) substrate with trichloroethylene at 85°C for 8 minutes, then clean it with deionized water at 85°C for 6 minutes. Immerse the substrate treated in the previous step 10 times in a mixed solution of potassium dichromate, concentrated sulfuric acid, and water at 85°C, with each immersion time being 2 seconds. The mass concentration of potassium dichromate in the mixed solution is 16 g / L, and the molar concentration of concentrated sulfuric acid is 11 mol / L. Then, clean it twice with deionized water at 85°C, with each cleaning time being 6 minutes. Immerse the substrate treated in the previous step in a mixed solution of sodium carbonate, sodium phosphate, and potassium hydroxide at 85°C for 3 minutes. The mass ratio of sodium carbonate, sodium phosphate, and potassium hydroxide in the mixed solution is 1:1:1. Then, immerse the substrate treated in the previous step sequentially in deionized water at 85°C, ammonia solution with a volume percentage of 28%, and deionized water at room temperature for 6 minutes each. Finally, clean the substrate treated in the previous step under isopropanol vapor reflux conditions for 6 minutes.

[0052] Step 4: Liquid phase epitaxy to grow thin films: Fix the substrate cleaned in Step 3 onto a platinum jig with an angle of 20° to the horizontal plane. Then, slowly place the platinum jig with the substrate into the furnace and preheat it for 10 minutes at a height of 30 mm above the melt surface. Then, completely immerse it in the melt and grow it for 10 minutes at a growth temperature of 853°C and a rotation speed of 65 rpm / min. After growth, quickly lift the substrate to a height of 20 mm from the melt surface and stop the process. Allow the substrate to cool naturally with the furnace. After cooling to room temperature, slowly remove the substrate from the epitaxial furnace. Finally, clean the obtained substrate with the thin film in a nitric acid:water mixture of 0.5:1 for 35 minutes to obtain the double-sided garnet single crystal thin film.

[0053] like Figure 5 As shown, Example 2 yielded a double-sided garnet single-crystal thin film with a thickness of 21 μm. Figure 6 This indicates that the obtained garnet single crystal thin film has high quality characteristics.

[0054] In the preparation method of double-sided garnet single crystal thin film for magneto-optical detection provided by the present invention, Bi2O3 serves as both a component and a flux for the thin film, and K2CO3 effectively reduces the surface tension of the melt. The resulting thin film has the characteristics of good matching with the substrate and high quality, and can be applied to magneto-optical detection devices.

[0055] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing double-sided garnet single-crystal thin films for magneto-optical detection, characterized in that, Includes the following steps: Step 1: Preparation of melt: Using Ga2O3, Tm2O3, Fe2O3, and Bi2O3 as raw materials, K2CO3 is added, and the mixture is stirred and melted to obtain a uniformly mixed melt; Among them, Bi2O3 provides both components and flux for the thin film, K2CO3 reduces the surface tension of the melt, and the specific gravity of Ga2O3, Tm2O3, Fe2O3 and Bi2O3 are (0.5%~1%), (1%~2%), (5%~6%) and (85%~95%), respectively, while the weight of K2CO3 is 0.5%~1.0% of the total weight. Step 2: Clean the substrate; Step 3, liquid phase epitaxy to grow thin film: Place the substrate cleaned in step 2 into the melt, grow at a temperature of 850-920°C, a substrate rotation speed of 50-110 rpm / min, for a growth time of 5-15 min. After growth, clean the substrate to obtain a double-sided garnet single crystal thin film for magneto-optical detection. In step 3, the angle between the substrate and the melt plane is 10-30°. After growth is completed, the substrate is quickly lifted to 20 mm from the melt surface and the process is stopped. The substrate is allowed to cool down naturally with the furnace. After cooling to room temperature, the substrate is slowly removed from the furnace. Finally, the substrate with the thin film is washed in a mixed solution of nitric acid and water for 30-45 min. The volume ratio of nitric acid to water is 0.5-1:

1.

2. The preparation method according to claim 1, characterized in that, The mixing steps include: putting Ga2O3, Tm2O3, Fe2O3, Bi2O3, and K2CO3 into a roller and mixing for 8 to 12 hours.

3. The preparation method according to claim 1, characterized in that, The melting process includes: placing one-third of the mixed raw materials into a crucible, melting at 1040–1050°C for 8–12 hours, holding at that temperature for 2–5 hours, and then cooling to below 100°C; then placing another one-third of the mixed raw materials into the crucible, melting at 1040–1050°C for 8–12 hours, holding at that temperature for 2–5 hours, and then cooling to below 100°C; finally placing one-third of the mixed raw materials into the crucible, melting at 1040–1050°C for 8–12 hours, holding at that temperature for 8–12 hours, and stirring at 1040–1050°C for 8–12 hours to obtain a uniformly mixed melt.

4. The preparation method according to claim 1, characterized in that, The substrate used in step 2 is a gadolinium gallium garnet (GGG) substrate.

5. The preparation method according to claim 1, characterized in that, The substrate cleaning process includes: Step 1: First, clean with trichloroethylene at 60-90℃ for 5-10 minutes, then clean with deionized water at 60-90℃ for 5-10 minutes. Step 2: Immerse the substrate treated in Step 1 in a mixed solution of potassium dichromate, concentrated sulfuric acid and water at 60-90°C 10-15 times, with each immersion lasting 1-3 seconds. Step 3: Clean the substrate treated in Step 2 twice with deionized water at 60-90℃, each time for 5-10 minutes. Step 4: Immerse the substrate treated in Step 3 in a mixed solution of sodium carbonate, sodium phosphate and potassium hydroxide at 60-90°C for 3-5 minutes. Step 5: Place the substrate treated in Step 4 into deionized water at 60-90℃, ammonia solution, and deionized water at room temperature for 5-10 minutes respectively. Step 6: Clean the substrate treated in step 5 under isopropanol vapor reflux conditions for 5-10 minutes.

6. The preparation method according to claim 5, characterized in that, In step 2, the mass concentration of potassium dichromate in the mixed solution is 15-20 g / L, and the molar concentration of concentrated sulfuric acid is 10-15 mol / L.

7. The preparation method according to claim 5, characterized in that, In step 4, the mass ratio of sodium carbonate, sodium phosphate, and potassium hydroxide in the mixed solution is 0.5–1:1:1; In step 5, the volume percentage of the ammonia solution is 25% to 35%.

8. A double-sided garnet single-crystal thin film for magneto-optical detection, characterized in that, The double-sided garnet single-crystal thin film for magneto-optical detection is prepared by the preparation method according to any one of claims 1-7, and the chemical formula of the thin film is (Bi x Tm 3-x (Ga) y Fe 5-y )O 12 , of which 0 <x<3,0<y<5。 9. The application of the double-sided garnet single-crystal thin film for magneto-optical detection according to claim 8 in magneto-optical detection devices.

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