Iron-doped gallium oxide-based strong ferromagnetic ceramic film material and preparation method thereof

Abstract

The application provides a kind of iron-doped gallium oxide-based strong ferromagnetic ceramic film material and a preparation method thereof, and relates to the technical field of magnetic semiconductor ceramic materials.The Ga organic precursor solution and the Fe organic precursor solution are prepared first;Then the Ga and Fe organic precursor solutions are mixed in a certain proportion to form a GaFe organic precursor solution;The GaFe organic precursor solution is spin-coated on a cleaned single-crystal alumina substrate;The obtained GaFe film is placed in a single-temperature zone tube furnace;In an air atmosphere, the temperature of the tube furnace is first increased to 550 DEG C at a slow rate of 2 DEG C / min, and then annealed for 1 h, and then increased to greater than or equal to 750 DEG C at the same heating rate for annealing treatment, and then annealed for 1 h, thereby preparing a GaFeO magnetic ceramic film with a very uniform surface and strong ferromagnetism.The preparation method of the application has low environmental requirements, and the GaFeO magnetic ceramic film prepared by the application has good crystallinity and crystalline orientation, excellent strong ferromagnetism, and a Curie temperature higher than 352 K.

Description

Technical Field

[0001] This invention relates to the field of magnetic semiconductor ceramic materials technology, and in particular to an iron-doped gallium oxide-based strong ferromagnetic ceramic thin film material and its preparation method. Background Technology

[0002] Gallium oxide (GaO) has attracted widespread attention in applications such as solar-blind optoelectronic devices and high-performance power devices due to its ultra-wide bandwidth, high breakdown electric field strength, and excellent optical properties. The ferromagnetism in GaO can be achieved by doping with various transition metals, which immediately sparked interest in GaO-based dilute magnetic semiconductors and related spintronic applications. Various types of dilute magnetic semiconductors have been extensively studied because they possess synergistic effects of semiconductor and magnetic properties within a single parent lattice, making them ideal for semiconductor spintronic materials and devices. However, practical applications of dilute magnetic semiconductors require at least two conditions: high Curie temperature and strong saturation magnetization. The Curie temperature should be above 300 K to ensure that devices based on dilute magnetic semiconductors can operate at room temperature. Fortunately, GaO doped with various transition metals (iron, manganese, nickel, chromium, and tin) exhibits Curie temperatures above room temperature. The magnitude of saturation magnetization is positively correlated with the switching speed of free-layer magnetization in spin-transfer torque; strong saturation magnetization can significantly improve the read / write capabilities of spin-transfer torque-based magnetic random access memories.

[0003] However, the saturation magnetization values ​​of gallium oxide obtained from experimental work to date remain low. Density functional theory calculations predict saturation magnetization values ​​of β-phase gallium oxide doped with single manganese, nickel, and zinc to be 4 μB, 3 μB, and 1 μB, respectively. However, in experiments, Ye et al. observed that Ni-doped β-phase gallium oxide (the most stable phase in gallium oxide), synthesized via hydrothermal synthesis and calcination, exhibits room-temperature ferromagnetism with a saturation magnetization value of 0.022 emu·cm. -3 (0.073 μB / Ni). Guo et al. prepared Cr-doped β-phase gallium oxide by pulsed laser deposition, exhibiting anisotropic ferromagnetism with saturation magnetization values ​​of 62.2 and 18.5 emu·cm, respectively. -3 (0.90 μB / Cr and 0.27 μB / Cr), which may contain secondary phases of metallic chromium and chromium-based oxides. In another study, Guo et al. reported a maximum saturation magnetization of 33.1 emu·cm in manganese-doped β-phase gallium oxide using laser molecular beam epitaxy. -3 (0.59 μB / Mn). Dai et al. found that, at the same doping concentration, oxygen vacancies (V OThe concentration of manganese (Mn) affects the magnitude of saturation magnetization; therefore, amorphous Mn-doped gallium oxide (GaO) films prepared by polymer-assisted deposition exhibit higher saturation magnetization. It has been reported that at moderate doping levels, the saturation magnetization of amorphous Mn-doped GaO films (1.18 μB / Mn) is higher than that of crystalline manganese-doped GaO films. However, at heavy doping levels above 30%, the saturation magnetization values ​​of amorphous Mn-doped GaO films and crystalline manganese-doped β-phase GaO films are the same, both around 31.0 emu·cm. -3 (0.51 μB / Mn). Huang et al. reported the highest saturation magnetization of 196.0 emu·cm for iron-doped γ-phase gallium oxide prepared by laser molecular beam epitaxy. -3 The curie temperature (5.73 μB / Fe) is higher than the theoretical prediction of 4.50 μB / Fe based on density functional theory calculations for γ-phase gallium oxide, due to the interaction between the dopant and defects such as Vos. However, γ-phase gallium oxide is unstable. Therefore, it is necessary to fabricate β-phase gallium oxide-based dilute magnetic semiconductors with high Curie temperatures and strong saturation magnetization in a simple and feasible manner for future applications in spintronic devices. Summary of the Invention

[0004] The purpose of this invention is to provide an iron-doped gallium oxide-based strong ferromagnetic ceramic thin film material and its preparation method. This preparation method is simple and easy to implement, significantly reduces costs, and has broad application prospects. Simultaneously, the prepared GaFeO magnetic ceramic thin film exhibits excellent crystallinity and crystal orientation, good surface smoothness, and a Curie temperature of 352K. The numerous technical effects of the preferred solutions among the various technical solutions provided by this invention are detailed below.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] In a first aspect, the present invention provides a method for preparing an iron-doped gallium oxide-based strongly ferromagnetic ceramic thin film material, comprising the following steps:

[0007] S1: Preparation of GaFe organic precursor solution: Add 5 to 34 parts by mass of Fe organic precursor solution to 100 parts by mass of Ga organic precursor solution and stir thoroughly to obtain GaFe organic precursor solution;

[0008] The method for preparing the Ga organic precursor solution includes: adding 2-15 parts by mass of polyethyleneimine and 1.5-15 parts by mass of ethylenediaminetetraacetic acid to 40 ml of deionized water, stirring thoroughly with a magnetic stirrer until transparent to obtain a polymer solution, and then adding 1-10 parts by mass of soluble gallium salt dropwise to the polymer solution and stirring thoroughly to obtain a Ga organic precursor solution with a molecular weight greater than 10000 g / mol.

[0009] The preparation method of the Fe organic precursor solution includes: adding 2-15 parts by mass of polyethyleneimine and 1.5-15 parts by mass of ethylenediaminetetraacetic acid to 40 ml of deionized water, stirring thoroughly with a magnetic stirrer until clear to obtain a polymer solution, and then adding 1-10 parts by mass of soluble iron salt dropwise to the polymer solution and stirring thoroughly to obtain an Fe organic precursor solution with a molecular weight greater than 10000 g / mol.

[0010] S2: Cleaning the substrate surface: Using single-crystal alumina as the substrate, clean it with ultrasonic waves for 5-15 minutes in acetone, alcohol and deionized water respectively, and finally dry it with a nitrogen gun.

[0011] S3: Spin coating: Spin coating the GaFe organic precursor solution obtained in step S1 onto the substrate described in step S2 to obtain a GaFe organic precursor film.

[0012] S4: Growth and heat treatment: The GaFe organic precursor film obtained in step S3 is placed in a single-temperature zone tube furnace; under an air atmosphere, the GaFe organic precursor film is first heated to 550℃ at a slow rate of 2℃ / min and held for 1h, and then heated to a temperature greater than or equal to 750℃ at a heating rate of 2℃ / min for heat treatment, held for 1h and then cooled to room temperature to prepare GaFeO magnetic ceramic film.

[0013] According to a preferred embodiment, in step S1, the soluble gallium salt includes gallium nitrate hydrate, and the soluble iron salt includes ferric nitrate hydrate.

[0014] According to a preferred embodiment, in step S1, the mass fraction of gallium nitrate hydrate is greater than 99.9%, the mass fraction of ferric nitrate hydrate is greater than 99.9%, the mass fraction of polyethyleneimine is greater than 99%, and the mass fraction of ethylenediaminetetraacetic acid is greater than 99.99%.

[0015] According to a preferred embodiment, in step S3, the spin coating step further includes: adjusting the thickness of the prepared GaFe organic precursor film by adjusting the spin coating speed and the number of spin coatings.

[0016] According to a preferred embodiment, the thin film is prepared by repeatedly performing step S3 followed by step S4 during multiple spin coating processes; or the thin film is prepared by alternating between performing steps S3 and S4.

[0017] Secondly, this application also provides an iron-doped gallium oxide-based strong ferromagnetic ceramic thin film material, which is prepared by the aforementioned preparation method.

[0018] According to a preferred embodiment, the iron-doped gallium oxide-based strongly ferromagnetic ceramic thin film material has room-temperature ferromagnetism and a Curie temperature above 352K.

[0019] Based on the above technical solution, the iron-doped gallium oxide-based strong ferromagnetic ceramic thin film material and its preparation method of the present invention have at least the following technical effects:

[0020] The method for preparing iron-doped gallium oxide-based strong ferromagnetic ceramic thin film materials of the present invention involves first preparing Ga organic precursor solutions and Fe organic precursor solutions, then thoroughly mixing the Ga and Fe organic precursor solutions in a certain proportion to form a GaFe organic precursor solution. The GaFe organic precursor solution is spin-coated onto a cleaned single-crystal alumina substrate. Then, under an air atmosphere, the temperature of a tube furnace is first raised to 550°C at a slow rate of 2°C / min and held for 1 hour. Subsequently, the temperature is raised to at least 750°C for annealing at the same rate and held for 1 hour. This process yields a GaFeO magnetic ceramic thin film with an extremely uniform surface and strong ferromagnetism. The preparation method of the present invention has low environmental requirements, and the control of the growth rate results in high-quality thin films. Furthermore, the doping with Fe gives the gallium oxide thin film an extremely stable long-range ferromagnetic order, indicating broad application prospects.

[0021] The GaFeO magnetic ceramic thin film prepared by this invention exhibits good crystallinity and crystal orientation, excellent strong ferromagnetism, and a Curie temperature above 352K. Furthermore, the preparation method has low environmental requirements, does not require a vacuum or sealed environment, and can react in air, thus greatly reducing costs. At the same time, the preparation method of this invention is simple and easy to implement, and has broad application prospects. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 The X-ray diffraction (XRD) patterns of GaFeO magnetic ceramic thin films prepared in air atmosphere in Examples 1-6 of this invention;

[0024] Figure 2 This is an atomic force microscope (AFM) image of a GaFeO magnetic ceramic thin film prepared in air atmosphere on an Al2O3 single crystal substrate with a (0001) crystal plane in Example 3 of the present invention.

[0025] Figure 3 The images are side and top scanning electron microscope (SEM) images of the interface between the GaFeO magnetic ceramic thin film and the alumina substrate prepared on an Al2O3 substrate with a (0001) crystal plane in air atmosphere after heat treatment at 750°C in Embodiment 3 of the present invention.

[0026] Figure 4 The X-ray photoelectron spectroscopy (XPS) spectra of GaFeO magnetic ceramic thin films prepared on Al2O3 substrates with (0001) crystal planes in air atmosphere after heat treatment at 750°C in Examples 1-6 of the present invention.

[0027] Figure 5 The X-ray photoelectron spectroscopy (XPS) spectra of the Fe 2p of GaFeO magnetic ceramic thin films prepared on an Al2O3 substrate with a (0001) crystal plane in air atmosphere after heat treatment at 750°C in Examples 2 and 5 of the present invention.

[0028] Figure 6 The O1s spectrum of the X-ray photoelectron spectroscopy (XPS) spectrum of GaFeO magnetic ceramic thin films prepared on Al2O3 substrates with (0001) crystal planes in air atmosphere after heat treatment at 750°C in Examples 1-6 of the present invention.

[0029] Figure 7 The temperature relationship curves of the magnetization intensity of GaFeO magnetic ceramic thin films prepared on Al2O3 substrates with (0001) crystal planes in air atmosphere after heat treatment at 750°C in Examples 1-6 of the present invention are shown (including field cooling and zero field cooling).

[0030] Figure 8 The GaFeO magnetic ceramic thin film prepared in air atmosphere on an Al2O3 substrate with (0001) crystal plane by heat treatment at 750°C is shown in Embodiment 5 of the present invention. The hysteresis loops are parallel to and perpendicular to the direction of the thin film. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0032] Example 1

[0033] This embodiment provides a method for preparing gallium oxide-based magnetic ceramic thin film materials, the specific steps of which are as follows:

[0034] Step S1: Preparation of Ga organic precursor solution: Add 2g of polyethylenediamine (PEI) and 1.5g of ethylenediaminetetraacetic acid (EDTA) to 40mL of deionized water, stir to dissolve, and then add 1.5g of gallium nitrate hydrate (Ga(NO3)3·xH2O) and stir for more than 6h. Use an ultrafiltration cup stirrer to ultrafilter the above solution, removing compounds with molecular weights below 10000g / mol under a pressure of 0.2MPa, to obtain the Ga organic precursor solution.

[0035] Step S2: Cleaning the substrate surface: Select single-crystal Al2O3 as the substrate, and clean it with ultrasonic waves in acetone, alcohol and deionized water for 15 minutes in sequence to remove organic matter and dust from the surface. Finally, blow it dry with a nitrogen gun.

[0036] Step S3: Spin coating: Spin coat the Ga organic precursor solution obtained in step S1 onto the substrate that has been cleaned in step S2. During spin coating, the spin coater speed is set to 3000 r / min and the spin coating time is 30 s.

[0037] Step 4: Heat treatment: The spin-coated film obtained in step S3 is placed in an air atmosphere and heat-treated for 1 hour at 750℃ to obtain a GaO magnetic ceramic film.

[0038] Example 2

[0039] This embodiment provides a method for preparing an iron-doped gallium oxide-based strongly ferromagnetic ceramic thin film material, the specific steps of which are as follows:

[0040] Step S1: Preparation of Ga organic precursor solution: Add 2g of polyethylenediamine (PEI) and 1.5g of ethylenediaminetetraacetic acid (EDTA) to 40mL of deionized water, stir to dissolve, and then add 1.5g of gallium nitrate hydrate (Ga(NO3)3·xH2O) and stir for more than 6h. Use an ultrafiltration cup stirrer to ultrafilter the above solution, removing compounds with molecular weights below 10000g / mol under a pressure of 0.2MPa.

[0041] Preparation of Fe organic precursor solution: 2 g of polyethylenediamine (PEI) and 1.5 g of ethylenediaminetetraacetic acid (EDTA) were added to 40 mL of deionized water and stirred until dissolved. Then, 1.5 g of ferric nitrate hydrate hydrate (FeN3O9·9H2O) was added and stirred for at least 6 h. The solution was then ultrafiltered using an ultrafiltration cup stirrer at a pressure of 0.2 MPa to remove compounds with molecular weights below 10000 g / mol.

[0042] Preparation of GaFe organic precursor solution: Add 5 parts of Fe organic precursor solution to 100 parts of Ga organic precursor solution and stir thoroughly to obtain GaFe organic precursor solution.

[0043] Step S2: Cleaning the substrate surface: Select single-crystal Al2O3 as the substrate, and clean it with ultrasonic waves in acetone, alcohol and deionized water for 15 minutes in sequence to remove organic matter and dust from the surface. Finally, blow it dry with a nitrogen gun.

[0044] Step S3: Spin coating: Spin coat the GaFe organic precursor solution obtained in step S1 onto the substrate cleaned in step S2. During spin coating, the spin coater speed is set to 3000 r / min and the spin coating time is 30 s.

[0045] Step 4: Heat treatment: Place the GaFe organic precursor film obtained in step S3 into a single-temperature zone tube furnace; under an air atmosphere, first heat the GaFe organic precursor film to 550℃ at a slow rate of 2℃ / min, hold for 1h, then heat it to 750℃ at a rate of 2℃ / min, hold for 1h, and then cool to room temperature to obtain GaFeO magnetic ceramic film.

[0046] Example 3

[0047] This embodiment provides a method for preparing an iron-doped gallium oxide-based strongly ferromagnetic ceramic thin film material, the specific steps of which are as follows:

[0048] Step S1: Preparation of Ga organic precursor solution: Add 2g of polyethylenediamine (PEI) and 1.5g of ethylenediaminetetraacetic acid (EDTA) to 40mL of deionized water, stir to dissolve, and then add 1.5g of gallium nitrate hydrate (Ga(NO3)3·xH2O) and stir for more than 6h. Use an ultrafiltration cup stirrer to ultrafilter the above solution, removing compounds with molecular weights below 10000g / mol under a pressure of 0.2MPa.

[0049] Preparation of Fe organic precursor solution: 2 g of polyethylenediamine (PEI) and 1.5 g of ethylenediaminetetraacetic acid (EDTA) were added to 40 mL of deionized water and stirred until dissolved. Then, 1.5 g of ferric nitrate hydrate hydrate (FeN3O9·9H2O) was added and stirred for at least 6 h. The solution was then ultrafiltered using an ultrafiltration cup stirrer at a pressure of 0.2 MPa to remove compounds with molecular weights below 10000 g / mol.

[0050] Preparation of GaFe organic precursor solution: Add 10 parts of Fe organic precursor solution to 100 parts of Ga organic precursor solution and stir thoroughly to obtain GaFe organic precursor solution.

[0051] Step S2: Cleaning the substrate surface: Select single-crystal Al2O3 as the substrate, and clean it with ultrasonic waves in acetone, alcohol and deionized water for 15 minutes in sequence to remove organic matter and dust from the surface. Finally, blow it dry with a nitrogen gun.

[0052] Step S3: Spin coating: Spin coat the GaFe organic precursor solution obtained in step S1 onto the substrate cleaned in step S2. During spin coating, the spin coater speed is set to 3000 r / min and the spin coating time is 30 s.

[0053] Step 4: Growth and heat treatment: Place the GaFe organic precursor film obtained in step S3 into a single-temperature zone tube furnace; under an air atmosphere, first heat the GaFe organic precursor film to 550°C at a slow rate of 2°C / min, hold for 1 hour, then heat it to 750°C at a rate of 2°C / min, hold for 1 hour, and then cool to room temperature.

[0054] Example 4

[0055] This embodiment provides a method for preparing an iron-doped gallium oxide-based strongly ferromagnetic ceramic thin film material, the specific steps of which are as follows:

[0056] Step S1: Preparation of Ga organic precursor solution: Add 2g of polyethylenediamine (PEI) and 1.5g of ethylenediaminetetraacetic acid (EDTA) to 40mL of deionized water, stir to dissolve, and then add 1.5g of gallium nitrate hydrate (Ga(NO3)3·xH2O) and stir for more than 6h. Use an ultrafiltration cup stirrer to ultrafilter the above solution, removing compounds with molecular weights below 10000g / mol under a pressure of 0.2MPa.

[0057] Preparation of Fe organic precursor solution: 2 g of polyethylenediamine (PEI) and 1.5 g of ethylenediaminetetraacetic acid (EDTA) were added to 40 mL of deionized water and stirred until dissolved. Then, 1.5 g of ferric nitrate hydrate hydrate (FeN3O9·9H2O) was added and stirred for at least 6 h. The solution was then ultrafiltered using an ultrafiltration cup stirrer at a pressure of 0.2 MPa to remove compounds with molecular weights below 10000 g / mol.

[0058] Preparation of GaFe organic precursor solution: Add 15 parts of Fe organic precursor solution to 100 parts of Ga organic precursor solution and stir thoroughly to obtain GaFe organic precursor solution.

[0059] Step S2: Cleaning the substrate surface: Select single-crystal Al2O3 as the substrate, and clean it with ultrasonic waves in acetone, alcohol and deionized water for 15 minutes in sequence to remove organic matter and dust from the surface. Finally, blow it dry with a nitrogen gun.

[0060] Step S3: Spin coating: Spin coat the GaFe organic precursor solution obtained in step S1 onto the substrate cleaned in step S2. During spin coating, the spin coater speed is set to 3000 r / min and the spin coating time is 30 s.

[0061] Step 4: Growth and heat treatment: The GaFe organic precursor film obtained in step S3 is placed in a single-temperature zone tube furnace; under an air atmosphere, the GaFe organic precursor film is first heated to 550°C at a slow rate of 2°C / min and held for 1 hour, then heated to 750°C at a rate of 2°C / min for heat treatment, held for 1 hour and then cooled to room temperature to obtain GaFeO magnetic ceramic film.

[0062] Example 5

[0063] This embodiment provides a method for preparing an iron-doped gallium oxide-based strongly ferromagnetic ceramic thin film material, the specific steps of which are as follows:

[0064] Step S1: Preparation of Ga organic precursor solution: Add 2g of polyethylenediamine (PEI) and 1.5g of ethylenediaminetetraacetic acid (EDTA) to 40mL of deionized water, stir to dissolve, and then add 1.5g of gallium nitrate hydrate (Ga(NO3)3·xH2O) and stir for more than 6h. Use an ultrafiltration cup stirrer to ultrafilter the above solution, removing compounds with molecular weights below 10000g / mol under a pressure of 0.2MPa.

[0065] Preparation of Fe organic precursor solution: 2 g of polyethylenediamine (PEI) and 1.5 g of ethylenediaminetetraacetic acid (EDTA) were added to 40 mL of deionized water and stirred until dissolved. Then, 1.5 g of ferric nitrate hydrate hydrate (FeN3O9·9H2O) was added and stirred for at least 6 h. The solution was then ultrafiltered using an ultrafiltration cup stirrer at a pressure of 0.2 MPa to remove compounds with molecular weights below 10000 g / mol.

[0066] Preparation of GaFe organic precursor solution: Add 21 parts of Fe organic precursor solution to 100 parts of Ga organic precursor solution and stir thoroughly to obtain GaFe organic precursor solution.

[0067] Step S2: Cleaning the substrate surface: Select single-crystal Al2O3 as the substrate, and clean it with ultrasonic waves in acetone, alcohol and deionized water for 15 minutes in sequence to remove organic matter and dust from the surface. Finally, blow it dry with a nitrogen gun.

[0068] Step S3: Spin coating: Spin coat the GaFe organic precursor solution obtained in step S1 onto the substrate cleaned in step S2. During spin coating, the spin coater speed is set to 3000 r / min and the spin coating time is 30 s.

[0069] Step 4: Growth and heat treatment: The GaFe organic precursor film obtained in step S3 is placed in a single-temperature zone tube furnace; under an air atmosphere, the GaFe organic precursor film is first heated to 550°C at a slow rate of 2°C / min and held for 1 hour, then heated to 750°C at a rate of 2°C / min for heat treatment, held for 1 hour and then cooled to room temperature to obtain GaFeO magnetic ceramic film.

[0070] Example 6

[0071] This embodiment provides a method for preparing an iron-doped gallium oxide-based strongly ferromagnetic ceramic thin film material, the specific steps of which are as follows:

[0072] Step S1: Preparation of Ga organic precursor solution: Add 2g of polyethylenediamine (PEI) and 1.5g of ethylenediaminetetraacetic acid (EDTA) to 40mL of deionized water, stir to dissolve, and then add 1.5g of gallium nitrate hydrate (Ga(NO3)3·xH2O) and stir for more than 6h. Use an ultrafiltration cup stirrer to ultrafilter the above solution, removing compounds with molecular weights below 10000g / mol under a pressure of 0.2MPa.

[0073] Preparation of Fe organic precursor solution: 2 g of polyethylenediamine (PEI) and 1.5 g of ethylenediaminetetraacetic acid (EDTA) were added to 40 mL of deionized water and stirred until dissolved. Then, 1.5 g of ferric nitrate hydrate hydrate (FeN3O9·9H2O) was added and stirred for at least 6 h. The solution was then ultrafiltered using an ultrafiltration cup stirrer at a pressure of 0.2 MPa to remove compounds with molecular weights below 10000 g / mol.

[0074] Preparation of GaFe organic precursor solution: Add 34 parts of Fe organic precursor solution to 100 parts of Ga organic precursor solution and stir thoroughly to obtain GaFe organic precursor solution.

[0075] Step S2: Cleaning the substrate surface: Select single-crystal Al2O3 as the substrate, and clean it with ultrasonic waves in acetone, alcohol and deionized water for 15 minutes in sequence to remove organic matter and dust from the surface. Finally, blow it dry with a nitrogen gun.

[0076] Step S3: Spin coating: Spin coat the GaFe organic precursor solution obtained in step S1 onto the substrate cleaned in step S2. During spin coating, the spin coater speed is set to 3000 r / min and the spin coating time is 30 s.

[0077] Step 4: Growth and heat treatment: The GaFe organic precursor film obtained in step S3 is placed in a single-temperature zone tube furnace; under an air atmosphere, the GaFe organic precursor film is first heated to 550°C at a slow rate of 2°C / min and held for 1 hour, then heated to 750°C at a rate of 2°C / min for heat treatment, held for 1 hour and then cooled to room temperature to obtain GaFeO magnetic ceramic film.

[0078] This invention used X-ray diffraction (XRD) technology to detect the phase composition of GaO and GaFeO magnetic ceramic films prepared in air atmosphere in Examples 1-6. The XRD diffraction patterns are shown below. Figure 1 As shown. From Figure 1 The XRD pattern on the left side shows that the GaFeO magnetic ceramic film prepared in this invention has three clear peaks, corresponding to the (-201), (-402), and (-603) peaks, respectively. This indicates that the GaFeO magnetic ceramic film prepared on the alumina substrate has a preferred (-201) orientation growing in one direction, and that the three peaks gradually shift to the left with increasing doping concentration (taking (-402) as an example). Figure 1 The XRD pattern on the right is shown.

[0079] Figure 2 This is an atomic force microscope (AFM) image of GaFeO magnetic ceramics prepared on an Al2O3 single-crystal substrate with a (0001) crystal plane according to Example 3 of the present invention. Figure 2 It can be seen that the surface of the prepared GaFeO magnetic ceramic film is uniform and continuous, with a surface roughness of about 0.19 nm, which is very smooth.

[0080] Figure 3 This is a side view of the interface between a GaFeO magnetic ceramic thin film and an alumina substrate prepared on an Al2O3 substrate with a (0001) crystal plane in air atmosphere after heat treatment at 750°C according to Embodiment 3 of the present invention. Figure 3 a) and looking down ( Figure 3 b- Figure 3 d) Scanning electron microscope (SEM) image. Figure 3 The side-view SEM image of a shows the uniform growth of a GaFeO magnetic ceramic film with a thickness of about 28 nm. Figure 3 The top-view SEM images from b to 3d show that the Ga, O, and Fe elements in the GaFeO magnetic ceramic film are distributed very uniformly, with no Fe agglomeration present.

[0081] Figure 4This is the full spectrum of the X-ray photoelectron spectroscopy (XPS) spectrum of GaFeO magnetic ceramic thin films prepared in air atmosphere on Al2O3 substrates with (0001) crystal planes by heat treatment at 750°C according to Examples 1-6 of the present invention. Figure 4 The spectrum shows that only Ga, O, Fe and C elements are detected in the GaFeO magnetic ceramic film. As the doping concentration increases, the peak of Fe element becomes more obvious. It can also be seen that the Fe 2p spectrum can be divided into two Fe subpeaks, corresponding to Fe2p1 / 2 and Fe 2p3 / 2, respectively.

[0082] Figure 5 The X-ray photoelectron spectroscopy (XPS) spectra of the Fe 2p of GaFeO magnetic ceramic thin films prepared on an Al2O3 substrate with a (0001) crystal plane in air atmosphere after heat treatment at 750°C according to Examples 2 and 5 of the present invention. Figure 5 The spectra show that both the Fe 2p 1 / 2 and Fe 2p 3 / 2 spectra can be divided into two Fe subpeaks, corresponding to Fe 2p1 / 2 and Fe 2p3 / 2 respectively. 2+ and Fe 3+ As the doping concentration increases, Fe 2+ and Fe 3+ The proportion of Fe in Examples 2 and 5 decreased continuously. 2+ and Fe 3+ The contents were 23:77 and 34:66, respectively.

[0083] Figure 6 This is the O1s spectrum of the X-ray photoelectron spectroscopy (XPS) spectra of GaFeO magnetic ceramic thin films prepared in air atmosphere on an Al2O3 substrate with a (0001) crystal plane by heat treatment at 750°C according to Examples 1-6 of the present invention. Figure 6 It can be observed that the O1s spectrum can be divided into two subpeaks located at approximately 530.70 eV and 532.10 eV, respectively, corresponding to lattice oxygen atoms and oxygen vacancies. From Figure 6 As can be seen, with the increase of Fe element concentration, the oxygen vacancy content of GaFeO magnetic ceramic film gradually increases, while the lattice oxygen content gradually decreases.

[0084] Figure 7 This is a temperature-dependent magnetization curve (including field cooling and zero-field cooling) of GaFeO magnetic ceramic thin films prepared in air atmosphere on an Al2O3 substrate with (0001) crystal planes under heat treatment at 750°C according to Examples 1-6 of the present invention. Figure 7It can be seen that with the increase of Fe concentration, the magnetization and Curie temperature of the GaFeO magnetic ceramic film also increase. Examples 1-6 all have cooling temperatures less than 45 K. Examples 5 and 6, with the highest Fe concentrations, have a temperature of 145.2 emu / cm³. 3 and 155.0 emu / cm 3 The saturation magnetization and Curie temperatures of 338 K and 352 K were observed. Specifically, the GaFeO magnetic ceramic films of Examples 5 and 6 exhibited Curie temperatures exceeding room temperature.

[0085] Figure 8 This is from Example 5 of the present invention, heat-treated at 750°C, showing the hysteresis loops parallel to and perpendicular to the film direction of a GaFeO magnetic ceramic thin film prepared in air atmosphere on an Al2O3 substrate with a (0001) crystal plane at room temperature. Figure 8 It can be seen that the GaFeO magnetic ceramic thin film of Example 5, prepared in air, has a saturation magnetization and coercivity of 55.0 emu / cm at room temperature (300 K). 3 The magnetic hysteresis loops parallel to and perpendicular to the film direction do not completely coincide, indicating that Example 5 exhibits a certain degree of anisotropy. Figure 8 This indicates that the GaFeO magnetic ceramic thin film prepared by the present invention has strong ferromagnetism at room temperature.

[0086] In summary, the GaFeO magnetic ceramic thin film prepared by the method of this invention exhibits good crystallinity and crystal orientation, good surface smoothness, and a Curie temperature above 352K. Furthermore, the preparation method of this invention has low environmental requirements, requiring no vacuum or sealed environment, and can react in air, thus greatly reducing costs and showing broad application prospects.

[0087] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing an iron-doped gallium oxide-based strong ferromagnetic ceramic thin film material, characterized in that, Includes the following steps: S1: Preparation of GaFe organic precursor solution: Add 5 to 34 parts by mass of Fe organic precursor solution to 100 parts by mass of Ga organic precursor solution and stir thoroughly to obtain GaFe organic precursor solution; The method for preparing the Ga organic precursor solution includes: adding 2-15 parts by mass of polyethyleneimine and 1.5-15 parts by mass of ethylenediaminetetraacetic acid to 40 ml of deionized water, stirring thoroughly with a magnetic stirrer until transparent to obtain a polymer solution, and then adding 1-10 parts by mass of soluble gallium salt dropwise to the polymer solution and stirring thoroughly to obtain a Ga organic precursor solution with a molecular weight greater than 10000 g / mol. The preparation method of the Fe organic precursor solution includes: adding 2-15 parts by mass of polyethyleneimine and 1.5-15 parts by mass of ethylenediaminetetraacetic acid to 40 ml of deionized water, stirring thoroughly with a magnetic stirrer until clear to obtain a polymer solution, and then adding 1-10 parts by mass of soluble iron salt dropwise to the polymer solution and stirring thoroughly to obtain an Fe organic precursor solution with a molecular weight greater than 10000 g / mol; S2: Cleaning the substrate surface: Using single-crystal alumina as the substrate, clean it with ultrasonic waves for 5-15 minutes in acetone, alcohol and deionized water respectively, and finally dry it with a nitrogen gun. S3: Spin coating: Spin coating the GaFe organic precursor solution obtained in step S1 onto the substrate described in step S2 to obtain a GaFe organic precursor film. S4: Growth and heat treatment: The GaFe organic precursor film obtained in step S3 is placed in a single-temperature zone tube furnace; under an air atmosphere, the GaFe organic precursor film is first heated to 550°C at a slow rate of 2°C / min and held for 1 hour, then heated to a temperature greater than or equal to 750°C at a heating rate of 2°C / min for heat treatment, held for 1 hour and then cooled to room temperature to prepare a GaFeO magnetic ceramic film. The iron-doped gallium oxide-based strong ferromagnetic ceramic film material has room temperature ferromagnetism and a Curie temperature higher than 352K.

2. The method for preparing iron-doped gallium oxide-based strong ferromagnetic ceramic thin film material according to claim 1, characterized in that, In step S1, the soluble gallium salt includes gallium nitrate hydrate, and the soluble iron salt includes ferric nitrate hydrate.

3. The preparation method according to claim 2, characterized in that, In step S1, the mass fraction of gallium nitrate hydrate is greater than 99.9%, the mass fraction of iron nitrate hydrate is greater than 99.9%, the mass fraction of polyethyleneimine is greater than 99%, and the mass fraction of ethylenediaminetetraacetic acid is greater than 99.99%.

4. The method for preparing iron-doped gallium oxide-based strong ferromagnetic ceramic thin film material according to claim 1, characterized in that, In step S3, the spin coating step further includes adjusting the thickness of the prepared GaFe organic precursor film by adjusting the spin coating speed and the number of spin coatings.

5. The method for preparing iron-doped gallium oxide-based strong ferromagnetic ceramic thin film material according to claim 4, characterized in that, In the process of multiple spin coatings, the thin film is prepared by repeatedly performing step S3 and then step S4; or by alternating between performing steps S3 and S4.

6. A gallium oxide-based iron-doped strong ferromagnetic ceramic thin film material, characterized in that, The iron-doped gallium oxide-based strong ferromagnetic ceramic thin film material is prepared by the preparation method described in any one of claims 1 to 5.

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