Method for enhancing Curie temperature of ultrathin nickel cobaltate film

Abstract

The invention discloses a method for enhancing the Curie temperature of an ultrathin nickel cobaltate film, and relates to the technical field of novel functional material processing, and the method comprises the following steps: S1, preparing a NiCo2O4 target material and a Co3O4 target material through a ceramic sintering process; s2, a NiCo2O4 / Co3O4 film is deposited on the MgAl2O4 (001) single crystal substrate through a magnetron sputtering method, and the NiCo2O4 / Co3O4 film is deposited on the MgAl2O4 (001) single crystal substrate; s3, the abnormal Hall effect of the grown NiCo2O4 / Co3O4 thin film is measured; according to the technical key points, the limitation of a traditional oxide hard magnetic material can be overcome, the NiCo2O4 / Co3O4 thin film is prepared by adopting a radio frequency magnetron sputtering preparation process and adopting NiCo2O4 and Co3O4 target materials, and the obtained thin film has the Curie temperature of 380K, has excellent conductivity and has a good use prospect.

Description

Technical Field

[0001] The invention relates to the technical field of novel functional material processing, in particular to a method for enhancing the Curie temperature of an ultra-thin nickel cobalt oxide film. Background Art

[0002] Spinel oxide is one of the typical representatives of transition metal oxide materials. There are two oxygen coordination structures and two connection modes in its crystal structure, which is conducive to the study of the mechanism of oxygen coordination structure. Spinel structure oxide has stable chemical properties, high hardness, high melting point, wear and corrosion resistance, excellent thermal conductivity and other advantages. It has great research value in the fields of superhard materials, magnetic materials, catalysts and conductive materials.

[0003] The anti-spinel ferromagnet NiCo2O4 (NCO) is an emerging material due to its unique physical properties, such as perpendicular magnetic anisotropy, excellent metallic conductivity, high spin polarization, and high transition temperature. In addition, the physical properties of NCO films can be easily tuned by changing the growth conditions due to the complex interplay between charge, spin, orbital, and lattice degrees of freedom. However, when the thickness of NCO films is reduced to a few atomic layers, their room temperature magnetic and electrical properties deteriorate, limiting their practical applications. Therefore, it is urgent to find a way to increase the Curie temperature (Tc) of nano / subnano NCO films.

[0004] In the prior art, although a variety of methods have been proposed to improve the performance of nickel cobalt oxide thin films, such as adjusting the synthesis conditions, doping with other metal ions, and using different preparation methods, there are still some challenges. The prior art often finds it difficult to maintain or improve conductivity while increasing the Curie temperature.

[0005] Therefore, the applicability of the existing solutions is not wide enough and does not meet people's usage requirements. To this end, we have developed a method to enhance the Curie temperature of ultra-thin nickel cobalt oxide films. Summary of the invention

[0006] 1. Technical issues to be solved

[0007] In view of the shortcomings of the prior art, the present invention provides a method for enhancing the Curie temperature of ultra-thin nickel cobalt oxide films, which can overcome the limitations of traditional oxide hard magnetic materials. By adopting a radio frequency magnetron sputtering preparation process and using NiCo2O4 and Co3O4 target materials, a NiCo2O4 / Co3O4 film is prepared. The obtained film has a Curie temperature of 380K and excellent conductivity, and has good application prospects.

[0008] (II) Technical solution

[0009] To achieve the above objectives, the present invention is implemented through the following technical solutions:

[0010] A method for enhancing the Curie temperature of an ultra-thin nickel cobalt oxide film comprises the following steps:

[0011] S1. Prepare NiCo2O4 target and Co3O4 target by ceramic sintering process;

[0012] S2. Depositing a NiCo2O4 / Co3O4 thin film on a MgAl2O4 (001) single crystal substrate by magnetron sputtering, and controlling the thickness of the film by sputtering time;

[0013] S3. The anomalous Hall effect of the grown NiCo2O4 / Co3O4 thin film was measured using a comprehensive physical property measurement system.

[0014] Preferably, the preparation method of the NiCo2O4 target and the Co3O4 target is as follows:

[0015] S11, raw material mixing: according to the requirements of the chemical reaction, the raw materials are weighed according to the stoichiometric ratio, and then the raw materials are put into a ball milling jar and ball milled together with zirconium dioxide balls on a ball mill;

[0016] When preparing NiCo2O4 target material, cobalt oxide and nickel oxide are accurately weighed according to the stoichiometric ratio of cobalt and nickel. When preparing Co3O4 target material, 15 to 30 grams of Co3O4 are weighed.

[0017] S12, pre-sintering: transferring the ball-milled raw materials into an alumina crucible, and then sintering them in a muffle furnace, and then cooling them;

[0018] S13, ball milling: ball milling the sintering material to obtain powder;

[0019] S14, granulation: adding 5% polyvinyl alcohol aqueous solution to the powder, and then grinding into fine particles;

[0020] The grinding in this step can be completed by manual grinding.

[0021] S15. Pressing and sintering: Use a tablet press to press the fine particles into a green body, then sinter it in an alumina crucible and cool it down.

[0022] Preferably, the ball milling time in step S11 is 1 to 5 hours, the sintering temperature in the muffle furnace in step S12 is 600° C. to 900° C., and the sintering time is 10 to 15 hours.

[0023] Preferably, the particle size after ball milling in step S13 is 10-100 μm, and the particle size range of fine particles ground in step S14 is 20 mesh-80 mesh.

[0024] Preferably, the sintering temperature in the alumina crucible in step S15 is 600° C. to 900° C., and the sintering time is 10 to 15 hours.

[0025] Preferably, the steps of depositing a NiCo2O4 / Co3O4 thin film on a MgAl2O4 (001) single crystal substrate by magnetron sputtering are as follows:

[0026] S21, substrate cleaning: cleaning and drying the substrate in sequence to remove oil stains on the surface of the substrate;

[0027] S22, vacuum treatment: placing the substrate on the base of the deposition chamber of the magnetron sputtering system and evacuating the chamber to ensure the purity and performance of the deposited film;

[0028] S23, heating treatment: heating the substrate to remove moisture from the surface of the substrate and improve the bonding strength between the film and the substrate;

[0029] S24, pressure adjustment: adjust the pressure of the magnetron sputtering system to 0.5-2 Pa to meet the pressure conditions of glow discharge;

[0030] S25, pre-sputtering: pre-sputter the target for 3 to 10 minutes to remove these impurities or surface oxide film on the target surface;

[0031] S26. Sputtering: The target material is subjected to magnetron sputtering. Ar+ is formed after ionizing argon gas under high pressure. Under the action of mutually perpendicular magnetic and electric fields, the movement speed of Ar+ increases rapidly and collides with the target material, thereby obtaining target material particles, which are finally accumulated to form a thin film.

[0032] Preferably, when cleaning the substrate in step S21, the substrate is immersed in a mixed liquid made of acetone, ethanol and deionized water, and cleaned by ultrasonic wave. The vacuum pressure in step S22 is 2×10 -4 Pa or above, the heating temperature in step S23 is 300-500°C.

[0033] Preferably, in step S26, the power of magnetron sputtering is 40 W, the rate is 14 nm / hour, and after magnetron sputtering, the temperature is kept at 420° C. for 30 minutes, and then cooled.

[0034] Preferably, the steps of measuring the anomalous Hall effect of the grown NiCo2O4 / Co3O4 film are as follows:

[0035] S31. Sample preparation: First, select a suitable sample and ensure that the sample meets the experimental requirements, such as shape, size, weight, etc. The measurement chamber of the PPMS equipment usually has certain size requirements for the sample. Then process the sample. Depending on the experimental needs, the sample may need to be annealed, cooled, or surface treated. Finally, calibrate the sample. Before measuring, the equipment can be calibrated with a standard sample to ensure the accuracy of the measurement results.

[0036] S32, Equipment preheating and calibration: First turn on the equipment, start the PPMS equipment and perform self-test to ensure the normal operation of the system. Check the hardware connection, sensor status, etc. Then preheat the system. If low-temperature measurement is required, start the liquid helium system and preheat it to the temperature required for the experiment. Finally, calibrate the sensor, calibrate the temperature, magnetic field, current, magnetic force and other sensors to ensure the accuracy of the measurement;

[0037] S33, sample installation: first fix the sample and carefully place it in the measurement sample chamber. According to different measurement methods (such as magnetic measurement, conductivity measurement), select a suitable sample clamping device to ensure that the sample is firm and not disturbed by the outside world. Then connect the electrodes: if measuring electrical properties (such as conductivity), the electrodes need to be in contact with the sample to ensure good electrical contact;

[0038] S34, set measurement parameters: temperature setting, set the target temperature according to the experimental needs, you can set a constant temperature or scan the temperature range. Magnetic field setting, if you are doing a magnetic test, set the strength and change mode of the magnetic field (such as scanning magnetic field, constant magnetic field, etc.). Measurement mode selection, select the appropriate measurement mode, such as temperature scanning, magnetic field scanning or current scanning, etc.;

[0039] S35, start measurement: start the measurement program, start the experimental software, set the data acquisition parameters and start the measurement. During the measurement process, make sure to monitor the real-time data and check whether the temperature, magnetic field, etc. are stable. Data acquisition and analysis, according to the set measurement conditions, the PPMS system will automatically collect and store data. You can view the experimental curve in real time and adjust the experimental parameters as needed;

[0040] S36, end measurement and data saving: complete the measurement, when the measurement is completed, stop data collection. The system will automatically generate measurement data and charts. Save and export data, save the measurement data to the computer, and export the data to DAT format for subsequent analysis;

[0041] S37, Sample removal and cleaning: Remove the sample and carefully remove it from the measurement chamber to avoid sample damage. Clean the equipment as needed, especially the sample chamber and electrode parts, to ensure the accuracy of the next measurement;

[0042] S38. Result analysis: Data processing, using the PPMS built-in software or other professional data processing software to analyze the experimental data and obtain the required physical parameters (such as conductivity, magnetization, etc.). Result verification, by comparing with standard data or repeating the experiment, verify the reliability of the measurement results.

[0043] (III) Beneficial effects

[0044] The present invention provides a method for enhancing the Curie temperature of an ultra-thin nickel cobalt oxide film, which has the following beneficial effects:

[0045] 1. The present invention provides a method for enhancing the Curie temperature of an ultra-thin nickel cobalt oxide film, which can overcome the limitations of traditional oxide hard magnetic materials. By adopting a preparation process of radio frequency magnetron sputtering, NiCo2O4 and Co3O4 targets are used to prepare a NiCo2O4 / Co3O4 film. The obtained film has a Curie temperature of 380K and excellent electrical conductivity, and has good application prospects.

[0046] 2. The present invention records a method for enhancing the Curie temperature of an ultra-thin nickel cobalt oxide film. The preparation method of the present invention is of great significance for promoting the application of magnetic oxide films in spin electronics, and can provide new possibilities for the research and development of high-density, high-speed and low-power magnetic storage devices; at the same time, the method has the advantage of low preparation material cost, which is conducive to large-scale preparation and industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 A schematic diagram of the structure of a NiCo2O4 / Co3O4 film provided in the present invention for enhancing the Curie temperature of an ultra-thin nickel cobalt oxide film;

[0048] Figure 2 The X-ray reflectivity and related fitting data of the NiCo2O4 / Co3O4 film in the method for enhancing the Curie temperature of an ultra-thin nickel cobalt oxide film of the present invention;

[0049] Figure 3 A magnetization curve diagram of a NiCo2O4 / Co3O4 film in a method for enhancing the Curie temperature of an ultra-thin nickel cobalt oxide film of the present invention;

[0050] Figure 4 The abnormal Hall curve of the NiCo2O4 / Co3O4 film changing with temperature in the method for enhancing the Curie temperature of the ultra-thin nickel cobalt oxide film of the present invention;

[0051] Figure 5 The RT curves of NiCo2O4 / Co3O4 film and single-layer NiCo2O4 in the method of enhancing the Curie temperature of ultra-thin nickel cobalt oxide film of the present invention are compared. DETAILED DESCRIPTION

[0052] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0053] A method for enhancing the Curie temperature of an ultra-thin nickel cobalt oxide film comprises the following steps:

[0054] Step 1: Prepare NiCo2O4 target material by standard ceramic sintering process. Add alcohol as grinding aid to NiO powder and Co3O4 powder in ball mill according to stoichiometric ratio, wet grind at 400 rpm for 40 min to mix evenly, and heat at 750℃ for 12 hours in muffle furnace at a heating rate of 5℃ per minute for the first sintering. Put the pre-sintered powder into ball mill again, dry grind at 200 rpm for 20 min, add binder, press into shape by tablet press at 20MPa for 15 min, and finally heat at 750℃ for 12 hours in muffle furnace at a heating rate of 5℃ per minute to obtain the desired ceramic target material.

[0055] The Co3O4 target was prepared by a standard ceramic sintering process. 20 grams of Co3O4 powder was accurately weighed and added with alcohol as a grinding aid in a ball mill. The mixture was wet-milled at 400 rpm for 40 minutes to mix evenly. The mixture was sintered for the first time at 750°C for 12 hours at a heating rate of 5°C per minute in a muffle furnace. The pre-sintered powder was put into a ball mill again and dry-milled at 200 rpm for 20 minutes. After that, a binder was added. The powder was pressed into shape by a tablet press at 20 MPa for 15 minutes. Finally, the desired ceramic target was sintered for the second time at 750°C for 12 hours at a heating rate of 5°C per minute in a muffle furnace.

[0056] Step 2: Immerse the MgAl2O4 substrate in alcohol and use an ultrasonic cleaning device to vibrate and clean it for 5 minutes. After the cleaned MgAl2O4 substrate is dried with nitrogen, it is immediately placed on the base of the deposition chamber of the magnetron sputtering system.

[0057] Step 3: Close the deposition chamber of the magnetron sputtering system, start the mechanical pump, open the valve connecting the mechanical pump and the chamber to evacuate, and start the resistance gauge to measure the pressure inside the chamber. When the pressure drops below 1×10Pa, close the connecting valve, open the molecular pump isolation valve, start the molecular pump and fully open the molecular pump plug valve to connect the molecular pump and the chamber. When the pressure drops to 1×10 -1 Pa, open the ionization gauge. When the vacuum degree reaches 1×10 -4Pa, a 1:1 argon / oxygen (Ar / O2) mixed gas is introduced, the gate valve opening is adjusted to keep the gas pressure at 1Pa, and then the substrate is heated to 420℃.

[0058] Step 4: First, a thin film is deposited on a MgAl2O4 (001) single crystal substrate using a Co3O4 target by magnetron sputtering. Then, a thin film is deposited on the Co3O4 film using a NiCo2O4 target (e.g. Figure 1 As shown), first adjust the power supply, start the RF power supply, keep the shutter closed for pre-sputtering for 5 minutes. After the pre-sputtering is completed, open the shutter to start sputtering, and control the thickness of the film by adjusting the sputtering time; specifically, the power of magnetron sputtering is 40w and the rate is 14nm / hour;

[0059] During magnetron sputtering, the composition uniformity and crystal quality of the film can be optimized by adjusting the sputtering energy, the appropriate temperature of the target material and the angle of the substrate.

[0060] Step 5: After the film is deposited, keep it at 420°C for 30 minutes to make its composition more uniform, and then cool it down to room temperature.

[0061] The obtained samples were subjected to XRD test (SmartLab SE model XRD diffraction instrument produced by Rigaku Corporation of Japan), magnetic measurement of MPMS3 and electrical transport measurement of PPMS (MPMS3 and PPMS are from QuantumDesign Corporation of the United States).

[0062] Atomic-scale interface engineering has become an important method to tune the physical properties of thin films. This is achieved by introducing interfacial coupling effects such as epitaxial strain, symmetry breaking, charge transfer, and orbital reconstruction. These findings provide an important way to manipulate the magnetic and transport properties of NCO films by regulating the valence and site occupancy of cations through interface engineering. Figure 1 As shown in Figure 2, we propose a NiCo2O4 / Co3O4 (NCO / CO) bilayer system that can significantly increase Tc (above room temperature) through interface engineering. This helps address the requirements of miniaturization and further promotes the application of NCO films as spintronic materials. It is found that the film resistance decreases sharply with increasing Co3O4 thickness. The observed phenomenon may be due to interface coupling leading to Ni 3+ The occupancy of ions at the octahedral sites increases, leading to an inherently linear relationship between resistivity and Curie temperature.

[0063] The test results are shown in the attached figure:

[0064] Figure 1 The structure of the NCO / CO thin film sample we grew is shown in the figure;

[0065] Figure 2 The X-ray reflectivity (XRR) of NCO, CO, and NCO / CO films is shown, showing a good correlation between time and thickness. The thicknesses of the NCO, CO, and NCO / CO films extracted are 3.1nm, 4.6nm, and 3.1nm / 4.6nm, respectively. The well-defined periodic oscillations observed in the XRR patterns indicate that the films all have an ordered periodic structure and clear interfaces.

[0066] Figure 3 The temperature-dependent in-plane (IP) and out-of-plane (OOP) magnetizations of the NCO (3.1 nm) / CO (4.6 nm) film after 2T field cooling are shown. In the out-of-plane direction, the magnetization is 0.18 μB / fu, close to 0, when the temperature is around 380 K, indicating that Tc reaches about 380 K, much higher than room temperature. This indicates that the insertion of the CO buffer layer leads to an increase in the Tc of the NCO / CO film, which is due to the charge transfer and interface coupling effects at the interface between CO and NCO.

[0067] Figure 4 The anomalous Hall effect was observed in the NCO / CO film. The typical anomalous Hall resistance of the 3.1nm thick NCO film and the 3.1nm / 4.6nm NCO / CO film varies with temperature as shown in Figure 2. Figure 4 As shown. Figure 4 As can be seen in a, when the temperature is 340K, a weak anomalous Hall effect can be observed, which proves that the Tc of the 3.1nm single-layer NCO film is 340K. Figure 4 As can be seen in b, a weak anomalous Hall effect can also be observed at a temperature of 380K, which further proves that the Tc of the 3.1nm / 4.6nm NCO / CO film has reached 380K, which is much higher than room temperature.

[0068] Figure 5 As shown, at room temperature, the sheet resistance of the 1.1nm NCO film with a CO buffer layer is reduced by two orders of magnitude compared to the single-layer NCO film, while the sheet resistance of the 3.1nm NCO film is reduced by two times. This indicates that the insertion of the CO buffer layer leads to a decrease in resistivity and an enhancement of conductivity in the NCO / CO film, which is due to the charge transfer and interfacial coupling effects at the interface between CO and NCO.

[0069] In summary, the present invention provides a method for enhancing the Curie temperature of an ultrathin nickel cobalt oxide film, and a high-quality NCO / CO heterostructure is grown on a MgAl2O4 (001) substrate. The results show that the Tc of the NCO / CO heterostructure (with a CO buffer layer) is significantly enhanced compared to a single-layer NCO film. In addition, a significant decrease in film resistance and enhanced conductivity were observed compared to a single-layer NCO film. The NCO / CO heterostructure also exhibits a clear anomalous Hall effect. The above demonstrates that interface coupling is an effective strategy for regulating the physical properties of oxides, opens up new opportunities for the application of NiCo2O4 materials in micro-spintronic devices, and is of great significance for promoting the application of magnetic oxide films in spintronics.

[0070] The present invention provides a method for enhancing the Curie temperature of an ultra-thin nickel cobalt oxide film, which can overcome the limitations of traditional oxide hard magnetic materials. A NiCo2O4 / Co3O4 film is prepared by adopting a preparation process of radio frequency magnetron sputtering and using NiCo2O4 and Co3O4 target materials. The obtained film has a Curie temperature of 380K and excellent electrical conductivity, and has good application prospects.

[0071] The present invention records a method for enhancing the Curie temperature of an ultra-thin nickel cobalt oxide film. The preparation method of the present invention is of great significance for promoting the application of magnetic oxide films in spin electronics, and can provide new possibilities for the research and development of high-density, high-speed and low-power magnetic storage devices; at the same time, the method has the advantage of low preparation material cost, which is conducive to large-scale preparation and industrial production.

[0072] The above embodiments may be implemented in whole or in part by software, hardware, firmware or any other combination thereof. When implemented using software, the above embodiments may be implemented in whole or in part in the form of a computer program product. A person of ordinary skill in the art may appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein may be implemented in electronic hardware, or in a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution.

[0073] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, and may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0074] The above description is only a specific implementation manner of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application.

Claims

1. A method for enhancing the Curie temperature of an ultra-thin nickel cobalt oxide film, characterized in that: The following steps are involved: S1. Prepare NiCo2O4 target and Co3O4 target by ceramic sintering process; S2, depositing NiCo2O4 / Co3O4 thin film on MgAl2O4 (001) single crystal substrate by magnetron sputtering; S3. Measure the anomalous Hall effect of the grown NiCo2O4 / Co3O4 film.

2. The method for enhancing the Curie temperature of an ultra-thin nickel cobalt oxide film according to claim 1, characterized in that: The preparation methods of the NiCo2O4 target and the Co3O4 target are as follows: S11, raw material mixing: weigh the raw materials according to the stoichiometric ratio, and then put the raw materials into a ball milling jar and mill them together with zirconium dioxide balls on a ball mill; S12, pre-sintering: transferring the ball-milled raw materials into an alumina crucible, and then sintering them in a muffle furnace, and then cooling them; S13, ball milling: ball milling the sintering material to obtain powder; S14, granulation: adding 5% polyvinyl alcohol aqueous solution to the powder, and then grinding into fine particles; S15. Pressing and sintering: Use a tablet press to press the fine particles into a green body, then sinter it in an alumina crucible and cool it down.

3. The method for enhancing the Curie temperature of an ultra-thin nickel cobalt oxide film according to claim 2, characterized in that: The ball milling time in step S11 is 1 to 5 hours, the sintering temperature in the muffle furnace in step S12 is 600° C. to 900° C., and the sintering time is 10 to 15 hours.

4. The method for enhancing the Curie temperature of an ultra-thin nickel cobalt oxide film according to claim 3, characterized in that: The particle size after ball milling in step S13 is 10-100 μm, and the particle size range of fine particles ground in step S14 is 20 mesh-80 mesh.

5. The method for enhancing the Curie temperature of an ultra-thin nickel cobalt oxide film according to claim 4, characterized in that: In step S15, the sintering temperature in the alumina crucible is 600° C. to 900° C., and the sintering time is 10 to 15 hours.

6. The method for enhancing the Curie temperature of an ultra-thin nickel cobalt oxide film according to claim 5, characterized in that: The steps of depositing a NiCo2O4 / Co3O4 thin film on a MgAl2O4 (001) single crystal substrate by magnetron sputtering are as follows: S21, substrate cleaning: cleaning and drying the substrate in sequence; S22, vacuum treatment: placing the substrate on a base in a deposition chamber of a magnetron sputtering system and evacuating the substrate; S23, heating treatment: heating the substrate to remove moisture from the surface of the substrate; S24, pressure adjustment: adjust the pressure of the magnetron sputtering system to 0.5-2 Pa; S25, pre-sputtering: pre-sputter the target for 3 to 10 minutes to remove these impurities or surface oxide film on the target surface; S26. Sputtering: performing magnetron sputtering on the target material.

7. The method for enhancing the Curie temperature of an ultra-thin nickel cobalt oxide film according to claim 6, characterized in that: In step S21, the substrate is cleaned by immersing the substrate in a mixed liquid of acetone, ethanol and deionized water and cleaning it by ultrasonic wave. In step S22, the vacuum pressure is 2×10 -4 Pa or above, the heating temperature in step S23 is 300-500°C.

8. The method for enhancing the Curie temperature of an ultra-thin nickel cobalt oxide film according to claim 7, characterized in that: In step S26, the power of magnetron sputtering is 40 W, and the rate is 14 nm / hour. After magnetron sputtering, the temperature is kept at 420° C. for 30 minutes, and then cooled.

9. The method for enhancing the Curie temperature of an ultra-thin nickel cobalt oxide film according to claim 8, characterized in that: The steps to measure the anomalous Hall effect of the grown NiCo2O4 / Co3O4 thin film are as follows: S31. Sample preparation: Cut the sample into the standard size of the experiment; S32, equipment preheating and calibration: start the equipment to perform self-test, check hardware connection, sensor status, and then preheat the system; S33, sample installation: fix the cut sample in the measurement sample chamber; S34, setting measurement parameters: setting parameters required for sample testing; S35, start measuring: measure, collect and store data during sample measurement; S36, end measurement and data saving: complete measurement, when the measurement is completed, stop data collection, generate measurement data and charts; S37, sample removal and cleaning: remove samples and clean equipment; S38. Result analysis: Data processing, use the software provided by PPMS or other professional data processing software to analyze the experimental data and obtain the required physical parameters.

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