Co-CoO single-layer amorphous-nanocrystalline exchange bias film and preparation method thereof

Abstract

The invention belongs to the technical field of magnetic functional materials, and particularly relates to a Co-CoO single-layer amorphous-nanocrystalline exchange bias film and a preparation method thereof. Comprising the following steps: providing a substrate; and heating the substrate at the heating temperature of 300K-573K, taking metal Co as a target material, and carrying out sputtering deposition on the substrate by utilizing magnetron sputtering to form the Co-CoO single-layer amorphous-nanocrystalline exchange bias film. The Co-CoO thin film is designed by adjusting the temperature of the substrate, the amorphous-nanocrystalline interface of the Co-CoO single-layer thin film can be regulated and controlled by changing the temperature of the substrate, and the interface synergistic effect and pinning behavior are improved, so that the exchange bias effect is influenced, and the excellent exchange bias effect can be obtained; and a foundation is laid for industrial application of the exchange bias effect in spin valves, magnetic recording media and spin electronic devices.

Description

Technical Field

[0001] The invention belongs to the technical field of magnetic functional materials, and in particular relates to a Co-CoO single-layer amorphous-nanocrystalline exchange bias film and a preparation method thereof. Background Art

[0002] Nanostructured materials possess distinct physical and chemical properties, and their appearance is particularly conducive to device miniaturization and application. However, as their size decreases, nanostructures reach their superparamagnetic limit and lose their stable magnetic order. This can be stabilized by introducing an exchange bias effect. The exchange bias effect refers to the phenomenon in which the hysteresis loop of a system with a ferromagnetic and antiferromagnetic interface shifts along the magnetic field axis under the influence of an external magnetic field. It has broad application prospects in spin valves, magnetic recording media, and spintronic devices. The exchange bias field is the displacement of the hysteresis loop from the origin along the magnetic field axis and can be used to measure the strength of the exchange bias effect.

[0003] Thin films have attracted widespread attention due to their advantages of simple preparation and easy miniaturization. Crystalline thin films are more mature in practical applications and have more theoretical support, but the crystal orientation, interface roughness and the existence of grain boundaries in crystal films greatly affect the exchange bias effect. Summary of the Invention

[0004] In order to solve the above problems, the present invention provides a Co-CoO single-layer amorphous-nanocrystalline exchange bias film and a preparation method thereof. By adjusting the substrate temperature, the amorphous-nanocrystalline interface in the film is regulated, and the interface synergy effect and pinning behavior are further improved, thereby enhancing the exchange bias performance.

[0005] The present invention solves the above technical problems through the following technical solutions.

[0006] In one aspect, the present invention provides a method for preparing a Co-CoO single-layer amorphous-nanocrystalline exchange bias film, comprising the following steps: A substrate is provided; the substrate is heated at a heating temperature of 300K to 573K; and a Co-CoO single-layer amorphous-nanocrystalline exchange bias film is formed on the substrate by sputtering deposition using metal Co as a target by magnetron sputtering.

[0007] Furthermore, during the sputtering deposition process, a mixed gas containing a reactive gas and a protective gas is introduced, and pre-sputtering is performed first, followed by sputtering deposition. The gas pressure of the pre-sputtering is 2Pa~3Pa, the sputtering power is 20W~30W, and the sputtering gas pressure of the sputtering deposition is 0.8Pa~1.4Pa, and the sputtering power is 20W~60W.

[0008] Furthermore, the mixed gas is oxygen and argon, and the oxygen partial pressure is 0.02% to 0.5% of the total gas pressure ratio of the mixed gas.

[0009] Furthermore, the sputtering deposition time is 10s to 1000s.

[0010] Furthermore, the vacuum degree during sputtering deposition is less than 2.5×10 -5 Pa.

[0011] Furthermore, the substrate is a wafer with crystal orientation or Si, Al2O3 or NaCl without crystal orientation.

[0012] Furthermore, before use, the substrate is ultrasonically cleaned in sequence with acetone, ethanol and / or water.

[0013] Furthermore, the purity of metallic Co is ≥99.95%.

[0014] On the other hand, the present invention provides a Co-CoO single-layer amorphous-nanocrystalline exchange bias film, which is prepared by the above-mentioned preparation method.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The preparation method provided by the present invention designs Co-CoO thin films by adjusting the substrate temperature. By changing the substrate temperature, the amorphous-nanocrystalline interface of the Co-CoO monolayer film can be regulated, the interface synergy and pinning behavior can be improved, thereby affecting the exchange bias effect. An excellent exchange bias effect can be obtained, laying the foundation for the industrial application of the exchange bias effect in spin valves, magnetic recording media and spintronic devices.

[0016] The preparation process of the present invention is simple and can be completed using existing simple magnetron sputtering equipment. The Co target and substrate used are easy to purchase, and the thin film sample obtained by sputtering does not require further processing.

[0017] The Co-CoO single-layer amorphous-nanocrystalline thin film sample prepared by the present invention has excellent exchange bias performance, breaking through the limitations of traditional ferromagnetic / antiferromagnetic double layers or particle composite systems. The maximum exchange bias field is 5.29kOe, which provides ideas for designing films with amorphous-nanocrystalline coexistence structure and regulating exchange bias behavior. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The figure is a flow chart for preparing the Co-CoO single-layer amorphous-nanocrystalline exchange bias film of the present invention.

[0019] Figure 2 This is a high-resolution transmission microscope image of the Co-CoO single-layer amorphous-nanocrystalline exchange bias film prepared in Examples 1 to 4 of the present invention. Figure 2 (a) is Example 1, (b) is Example 2, (c) is Example 3, and (d) is Example 4.

[0020] Figure 3 hysteresis loop diagram of the Co-CoO single-layer amorphous-nanocrystalline exchange bias film prepared in Examples 1 to 4 of the present invention, Figure 3 (a) is Example 1, (b) is Example 2, (c) is Example 3, and (d) is Example 4.

[0021] Figure 4 Statistical graphs of the hysteresis loops of the Co-CoO single-layer amorphous-nanocrystalline exchange bias films prepared in Examples 1 to 4 of the present invention.

[0022] Figure 5 This is a statistical diagram of the exchange bias field of the Co-CoO single-layer amorphous-nanocrystalline exchange bias film prepared in Example 2 of the present invention as a function of the cooling field.

[0023] Figure 6 hysteresis loop diagram of the Co-CoO single-layer amorphous-nanocrystalline exchange bias film prepared in Examples 5 to 8 of the present invention, Figure 6 Among them, (a) is Example 5, (b) is Example 6, (c) is Example 7, and (d) is Example 8. DETAILED DESCRIPTION

[0024] The following will provide a clear and complete description of the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0025] It should be noted that the professional terms used in the present invention are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention. Unless otherwise specified, the various raw materials, reagents, instruments and equipment used in the following embodiments of the present invention can be purchased from the market or prepared by existing methods.

[0026] The present invention provides a method for preparing a Co-CoO single-layer amorphous-nanocrystalline exchange bias film. The amorphous film has low local magnetic anisotropy, a disordered atomic structure, and the absence of grain boundaries, making its magnetization direction more easily changeable, thereby enabling rapid magnetic response to small magnetic fields. By combining two materials with different structures, amorphous and nanocrystalline, the present invention can fully leverage the advantages of both, facilitating excellent exchange bias performance. The amorphous-nanocrystalline interface in the film is regulated by adjusting the substrate temperature, further improving the interface synergy and pinning behavior, thereby enhancing exchange bias performance. The method comprises the following steps: providing a substrate; heating the substrate to a temperature of 300K to 573K; and using metal Co as a target to form a Co-CoO single-layer amorphous-nanocrystalline exchange bias film by sputtering and depositing it on the substrate using magnetron sputtering.

[0027] More specifically, the preparation method of Co-CoO single layer amorphous-nanocrystalline exchange bias film is as follows: Figure 1 As shown, the following steps are included: Step 1: Place the substrate and Co target in the sputtering chamber of the magnetron sputtering equipment, and then evacuate the sputtering chamber. First, use a mechanical pump to evacuate the sputtering chamber to below 10 Pa, then open the solenoid valve and molecular pump in sequence to evacuate the background vacuum of the magnetron sputtering equipment to 2.5×10 -5 Below Pa.

[0028] Step 2: Set the substrate temperature as desired. After connecting the thermocouple circuit, turn on the heater and set the heating temperature to a range of 300K to 573K. Once the temperature sensor reaches the specified temperature, allow it to stabilize for 30 minutes to ensure the substrate temperature remains consistent with the temperature sensor.

[0029] Step 3: introduce sputtering gas argon into the sputtering chamber as a protective gas, and then introduce oxygen as a reaction gas, control the oxygen partial pressure ratio of the mixed gas to 0.02% to 0.5%, adjust the molecular pump gate valve to control the pressure in the sputtering chamber to 2Pa to 3Pa, connect the DC power supply to the Co target, glow the Co target with a DC power of 20W to 30W, perform pre-sputtering for 10 minutes to clean the Co target and wait for the glow to stabilize; adjust the sputtering pressure to 0.8Pa to 1.4Pa through the molecular pump gate valve, adjust the baffle position to align the substrate with the Co target, and deposit a Co-CoO single-layer film on the substrate with a DC power of 20W to 60W, and the sputtering time is 10s to 1000s.

[0030] After sputtering deposition, the sample must be cooled to room temperature before being removed from the magnetron sputtering equipment to prevent further oxidation. The preparation process is simple and can be completed using existing, simple magnetron sputtering equipment. The Co target and substrate used are readily available, and the sputtered thin film samples require no further processing.

[0031] By adopting the above preparation method and adjusting the substrate temperature to design Co-CoO thin films, as the substrate temperature gradually increases, the film transforms from amorphous to nanocrystalline, where CoO forms nanocrystals before Co. Therefore, changing the substrate temperature can regulate the amorphous-nanocrystalline interface of the Co-CoO monolayer film, improve the interface synergy and pinning behavior, thereby affecting the exchange bias effect, and obtaining an excellent exchange bias effect, laying the foundation for the industrial application of the exchange bias effect in spin valves, magnetic recording media and spintronic devices.

[0032] In some embodiments, the substrate includes but is not limited to a wafer with an orientation or Si, Al2O3 or NaCl without an orientation.

[0033] In some embodiments, the substrate is ultrasonically cleaned with acetone, ethanol, and / or water for 10 minutes before use. When the substrate is NaCl, ethanol is used instead of deionized water for cleaning to prevent the NaCl substrate from dissolving in the deionized water.

[0034] In some embodiments, the purity of metallic Co is ≥99.95%.

[0035] In another aspect, the present invention provides a Co-CoO single-layer amorphous-nanocrystalline exchange-biased thin film. The Co-CoO single-layer amorphous-nanocrystalline thin film sample prepared by the present invention exhibits excellent exchange bias performance, surpassing the limitations of traditional ferromagnetic / antiferromagnetic bilayer or particle composite systems. The maximum exchange bias field is 5.29 kOe, providing insights into the design of thin films with coexisting amorphous-nanocrystalline structures and the regulation of exchange bias behavior.

[0036] The following is further described through specific examples.

[0037] Example 1 A method for preparing a Co-CoO single-layer amorphous-nanocrystalline exchange bias film comprises the following steps: Step 1: Provide a Si substrate and ultrasonically clean the Si substrate with acetone, ethanol, and deionized water for ten minutes to remove impurities and oil on the substrate surface. Then, place a Co target with a purity of 99.95% and the pretreated substrate into the sputtering chamber of the magnetron sputtering equipment. After closing the chamber, first use a mechanical pump to evacuate the sputtering chamber to below 10 Pa, then open the solenoid valve and molecular pump in sequence to evacuate the background vacuum of the magnetron sputtering equipment to 2.5×10 -5 Below Pa.

[0038] Step 2: After connecting the thermocouple loop, turn on the heating power supply, set the heating temperature to 300K, and heat the Si substrate to 300K. When the temperature sensor reaches the specified temperature, stabilize it for 30 minutes to ensure that the substrate temperature remains consistent with the temperature sensor.

[0039] In step 3, argon gas is introduced into the sputtering chamber, followed by oxygen as the reaction gas, with the oxygen partial pressure controlled to 0.02% of the total gas pressure. The molecular pump gate valve is adjusted to control the pressure in the sputtering chamber to 2 Pa. A DC power supply is connected to the Co target, and the Co target is glowed with a DC power of 20 W. A 10-minute pre-sputtering is performed to clean the Co target and wait for the glow to stabilize. In the argon-oxygen mixed atmosphere, the sputtering pressure is adjusted to 0.8 Pa using the molecular pump gate valve. The baffle position is adjusted to align the substrate with the Co target. A Co-CoO monolayer thin film is deposited on the substrate with a DC power of 20 W for 100 seconds. After the sputtering deposition is completed, the sample is cooled to room temperature before being removed from the magnetron sputtering equipment to prevent further oxidation of the sample, thereby obtaining a Co-CoO monolayer amorphous-nanocrystalline exchange bias thin film.

[0040] Example 2 A method for preparing a Co-CoO single-layer amorphous-nanocrystalline exchange bias film comprises the following steps: Step 1: Provide a Si substrate and ultrasonically clean the Si substrate with acetone, ethanol, and deionized water for ten minutes to remove impurities and oil on the substrate surface. Then, place a Co target with a purity of 99.95% and the pretreated substrate into the sputtering chamber of the magnetron sputtering equipment. After closing the chamber, first use a mechanical pump to evacuate the sputtering chamber to below 10 Pa, then open the solenoid valve and molecular pump in sequence to evacuate the background vacuum of the magnetron sputtering equipment to 2.5×10 -5 Below Pa.

[0041] Step 2: After connecting the thermocouple loop, turn on the heating power supply, set the heating temperature to 373K, and heat the Si substrate to 373K. When the temperature sensor reaches the specified temperature, stabilize it for 30 minutes to keep the substrate temperature consistent with the temperature sensor.

[0042] In step 3, argon gas is introduced into the sputtering chamber, followed by oxygen as the reaction gas, with the oxygen partial pressure controlled to 0.02% of the total gas pressure. The molecular pump gate valve is adjusted to control the pressure in the sputtering chamber to 2 Pa. A DC power supply is connected to the Co target, and the Co target is glowed with a DC power of 20 W. A 10-minute pre-sputtering is performed to clean the Co target and wait for the glow to stabilize. In the argon-oxygen mixed atmosphere, the sputtering pressure is adjusted to 0.8 Pa using the molecular pump gate valve. The baffle position is adjusted to align the substrate with the Co target. A Co-CoO monolayer thin film is deposited on the substrate with a DC power of 20 W for 100 seconds. After the sputtering deposition is completed, the sample is cooled to room temperature before being removed from the magnetron sputtering equipment to prevent further oxidation of the sample, thereby obtaining a Co-CoO monolayer amorphous-nanocrystalline exchange bias thin film.

[0043] Example 3 A method for preparing a Co-CoO single-layer amorphous-nanocrystalline exchange bias film comprises the following steps: Step 1: Provide a Si substrate and ultrasonically clean the Si substrate with acetone, ethanol, and deionized water for ten minutes to remove impurities and oil on the substrate surface. Then, place a Co target with a purity of 99.95% and the pretreated substrate into the sputtering chamber of the magnetron sputtering equipment. After closing the chamber, first use a mechanical pump to evacuate the sputtering chamber to below 10 Pa, then open the solenoid valve and molecular pump in sequence to evacuate the background vacuum of the magnetron sputtering equipment to 2.5×10 -5 Below Pa.

[0044] Step 2: After connecting the thermocouple loop, turn on the heating power supply, set the heating temperature to 473K, and heat the Si substrate to 473K. When the temperature sensor reaches the specified temperature, stabilize it for 30 minutes to ensure that the substrate temperature remains consistent with the temperature sensor.

[0045] In step 3, argon gas is introduced into the sputtering chamber, followed by oxygen as the reaction gas, with the oxygen partial pressure controlled to 0.02% of the total gas pressure. The molecular pump gate valve is adjusted to control the pressure in the sputtering chamber to 2 Pa. A DC power supply is connected to the Co target, and the Co target is glowed with a DC power of 20 W. A 10-minute pre-sputtering is performed to clean the Co target and wait for the glow to stabilize. In the argon-oxygen mixed atmosphere, the sputtering pressure is adjusted to 0.8 Pa using the molecular pump gate valve. The baffle position is adjusted to align the substrate with the Co target. A Co-CoO monolayer thin film is deposited on the substrate with a DC power of 20 W for 100 seconds. After the sputtering deposition is completed, the sample is cooled to room temperature before being removed from the magnetron sputtering equipment to prevent further oxidation of the sample, thereby obtaining a Co-CoO monolayer amorphous-nanocrystalline exchange bias thin film.

[0046] Example 4 A method for preparing a Co-CoO single-layer amorphous-nanocrystalline exchange bias film comprises the following steps: Step 1: Provide a Si substrate and ultrasonically clean the Si substrate with acetone, ethanol, and deionized water for ten minutes to remove impurities and oil on the substrate surface. Then, place a Co target with a purity of 99.95% and the pretreated substrate into the sputtering chamber of the magnetron sputtering equipment. After closing the chamber, first use a mechanical pump to evacuate the sputtering chamber to below 10 Pa, then open the solenoid valve and molecular pump in sequence to evacuate the background vacuum of the magnetron sputtering equipment to 2.5×10 -5 Below Pa.

[0047] Step 2: After connecting the thermocouple loop, turn on the heating power supply and set the heating temperature to 573K. Heat the Si substrate to 573K. When the temperature sensor reaches the specified temperature, stabilize it for 30 minutes to keep the substrate temperature consistent with the temperature sensor.

[0048] In step 3, argon gas is introduced into the sputtering chamber, followed by oxygen as the reaction gas, with the oxygen partial pressure controlled to 0.02% of the total gas pressure. The molecular pump gate valve is adjusted to control the pressure in the sputtering chamber to 2 Pa. A DC power supply is connected to the Co target, and the Co target is glowed with a DC power of 20 W. A 10-minute pre-sputtering is performed to clean the Co target and wait for the glow to stabilize. In the argon-oxygen mixed atmosphere, the sputtering pressure is adjusted to 0.8 Pa using the molecular pump gate valve. The baffle position is adjusted to align the substrate with the Co target. A Co-CoO monolayer thin film is deposited on the substrate with a DC power of 20 W for 100 seconds. After the sputtering deposition is completed, the sample is cooled to room temperature before being removed from the magnetron sputtering equipment to prevent further oxidation of the sample, thereby obtaining a Co-CoO monolayer amorphous-nanocrystalline exchange bias thin film.

[0049] Example 5 A method for preparing a Co-CoO single-layer amorphous-nanocrystalline exchange bias film comprises the following steps: Step 1: Provide a Si substrate and ultrasonically clean the Si substrate with acetone, ethanol, and deionized water for ten minutes to remove impurities and oil on the substrate surface. Then, place a Co target with a purity of 99.95% and the pretreated substrate into the sputtering chamber of the magnetron sputtering equipment. After closing the chamber, first use a mechanical pump to evacuate the sputtering chamber to below 10 Pa, then open the solenoid valve and molecular pump in sequence to evacuate the background vacuum of the magnetron sputtering equipment to 2.5×10 -5 Below Pa.

[0050] Step 2: After connecting the thermocouple loop, turn on the heating power supply, set the heating temperature to 300K, and then heat the Si substrate to 300K. When the temperature sensor reaches the specified temperature, stabilize it for 30 minutes to ensure that the substrate temperature remains consistent with the temperature sensor.

[0051] In step 3, argon gas is introduced into the sputtering chamber, followed by oxygen as the reaction gas, with the oxygen partial pressure controlled to 0.02% of the total gas pressure. The molecular pump gate valve is adjusted to control the pressure in the sputtering chamber to 2.5 Pa. A DC power supply is connected to the Co target, and the Co target is glowed at a DC power of 30 W. A 10-minute pre-sputtering is performed to clean the Co target and wait for the glow to stabilize. In the argon-oxygen mixed atmosphere, the sputtering pressure is adjusted to 1.4 Pa using the molecular pump gate valve. The baffle position is adjusted to align the substrate with the Co target. A Co-CoO monolayer thin film is deposited on the substrate at a DC power of 30 W for 100 seconds. After the sputtering deposition is completed, the sample is cooled to room temperature before being removed from the magnetron sputtering equipment to prevent further oxidation of the sample, thereby obtaining a Co-CoO monolayer amorphous-nanocrystalline exchange bias thin film.

[0052] Example 6 A method for preparing a Co-CoO single-layer amorphous-nanocrystalline exchange bias film comprises the following steps: Step 1: Provide a Si substrate and ultrasonically clean the Si substrate with acetone, ethanol, and deionized water for ten minutes to remove impurities and oil on the substrate surface. Then, place a Co target with a purity of 99.95% and the pretreated substrate into the sputtering chamber of the magnetron sputtering equipment. After closing the chamber, first use a mechanical pump to evacuate the sputtering chamber to below 10 Pa, then open the solenoid valve and molecular pump in sequence to evacuate the background vacuum of the magnetron sputtering equipment to 2.5×10 -5 Below Pa.

[0053] Step 2: After connecting the thermocouple loop, turn on the heating power supply, set the heating temperature to 300K, and then heat the Si substrate to 300K. When the temperature sensor reaches the specified temperature, stabilize it for 30 minutes to ensure that the substrate temperature remains consistent with the temperature sensor.

[0054] In step 3, argon gas is introduced into the sputtering chamber, followed by oxygen as the reaction gas, with the oxygen partial pressure controlled to 0.02% of the total gas pressure. The molecular pump gate valve is adjusted to control the pressure in the sputtering chamber to 2.5 Pa. A DC power supply is connected to the Co target, and the Co target is glowed at a DC power of 30 W. A 10-minute pre-sputtering is performed to clean the Co target and wait for the glow to stabilize. In the argon-oxygen mixed atmosphere, the sputtering pressure is adjusted to 1.4 Pa using the molecular pump gate valve. The baffle position is adjusted to align the substrate with the Co target. A Co-CoO monolayer thin film is deposited on the substrate at a DC power of 40 W for 100 seconds. After the sputtering deposition is completed, the sample is cooled to room temperature before being removed from the magnetron sputtering equipment to prevent further oxidation of the sample, thereby obtaining a Co-CoO monolayer amorphous-nanocrystalline exchange bias thin film.

[0055] Example 7 A method for preparing a Co-CoO single-layer amorphous-nanocrystalline exchange bias film comprises the following steps: Step 1: Provide a Si substrate and ultrasonically clean the Si substrate with acetone, ethanol, and deionized water for ten minutes to remove impurities and oil on the substrate surface. Then, place a Co target with a purity of 99.95% and the pretreated substrate into the sputtering chamber of the magnetron sputtering equipment. After closing the chamber, first use a mechanical pump to evacuate the sputtering chamber to below 10 Pa, then open the solenoid valve and molecular pump in sequence to evacuate the background vacuum of the magnetron sputtering equipment to 2.5×10 -5 Below Pa.

[0056] Step 2: After connecting the thermocouple loop, turn on the heating power supply, set the heating temperature to 300K, and heat the Si substrate to 300K. When the temperature sensor reaches the specified temperature, stabilize it for 30 minutes to ensure that the substrate temperature remains consistent with the temperature sensor.

[0057] Step 3: Argon is introduced into the sputtering chamber as a sputtering gas, followed by oxygen as a reaction gas, with the oxygen partial pressure controlled to 0.02% of the total gas pressure. The molecular pump gate valve is adjusted to control the pressure in the sputtering chamber to 2.5 Pa. A DC power supply is connected to the Co target, and the Co target is ignited with a DC power of 30 W. A 10-minute pre-sputtering is performed to clean the Co target and wait for the glow to stabilize. In the argon-oxygen mixed atmosphere, the sputtering pressure is adjusted to 1.4 Pa using the molecular pump gate valve. The baffle position is adjusted to align the substrate with the Co target. A Co-CoO monolayer thin film is deposited on the substrate with a DC power of 50 W for 100 seconds. After the sputtering deposition is completed, the sample is cooled to room temperature before being removed from the magnetron sputtering equipment to prevent further oxidation of the sample, thereby obtaining a Co-CoO monolayer amorphous-nanocrystalline exchange bias thin film.

[0058] Example 8 A method for preparing a Co-CoO single-layer amorphous-nanocrystalline exchange bias film comprises the following steps: Step 1: Provide a Si substrate and ultrasonically clean the Si substrate with acetone, ethanol, and deionized water for ten minutes to remove impurities and oil on the substrate surface. Then, place a Co target with a purity of 99.95% and the pretreated substrate into the sputtering chamber of the magnetron sputtering equipment. After closing the chamber, first use a mechanical pump to evacuate the sputtering chamber to below 10 Pa, then open the solenoid valve and molecular pump in sequence to evacuate the background vacuum of the magnetron sputtering equipment to 2.5×10 -5 Below Pa.

[0059] Step 2: After connecting the thermocouple loop, turn on the heating power supply, set the heating temperature to 300K, and heat the Si substrate to 300K. When the temperature sensor reaches the specified temperature, stabilize it for 30 minutes to ensure that the substrate temperature remains consistent with the temperature sensor.

[0060] Step 3: Argon is introduced into the sputtering chamber as a sputtering gas, followed by oxygen as a reaction gas, with the oxygen partial pressure controlled to 0.02% of the total gas pressure. The molecular pump gate valve is adjusted to control the pressure in the sputtering chamber to 2.5 Pa. A DC power supply is connected to the Co target, and the Co target is ignited with a DC power of 30 W. A 10-minute pre-sputtering is performed to clean the Co target and wait for the glow to stabilize. In the argon-oxygen mixed atmosphere, the sputtering pressure is adjusted to 1.4 Pa using the molecular pump gate valve. The baffle position is adjusted to align the substrate with the Co target. A Co-CoO monolayer thin film is deposited on the substrate with a DC power of 60 W for 100 seconds. After the sputtering deposition is completed, the sample is cooled to room temperature before being removed from the magnetron sputtering equipment to prevent further oxidation of the sample, thereby obtaining a Co-CoO monolayer amorphous-nanocrystalline exchange bias thin film.

[0061] The structure and performance of the Co-CoO single-layer amorphous-nanocrystalline exchange bias films prepared in Examples 1 to 8 were tested. The results are as follows:

[0062] Figure 2 This is a high-resolution transmission microscope image of the Co-CoO single-layer amorphous-nanocrystalline exchange bias film prepared in Examples 1 to 4 of the present invention. Figure 2 (a) is Example 1, (b) is Example 2, (c) is Example 3, and (d) is Example 4. Figure 2 As shown in the figure, the coexistence of amorphous and nanocrystals exists in the Co-CoO films deposited at substrate temperatures of 300K, 373K, 473K and 573K. With the increase of substrate temperature, the degree of nanocrystals in the film gradually increases. Compared with Co, CoO can form nanocrystals at lower substrate temperatures.

[0063] The Co—CoO single-layer amorphous-nanocrystalline exchange bias films prepared in Examples 1 to 4 were magnetically characterized using an MPMS-3 magnetic measurement system developed and produced by Quantum Design, Inc., USA. The samples were placed in the magnetic measurement system and evacuated. Under the action of a 10 kOe cooling field, the temperature was lowered to 10 K at a cooling rate of 30 K / min, and then the hysteresis loops were measured. Figure 3 hysteresis loop diagram of the Co-CoO single-layer amorphous-nanocrystalline exchange bias film prepared in Examples 1 to 4 of the present invention, Figure 3 (a) is Example 1, (b) is Example 2, (c) is Example 3, and (d) is Example 4. Figure 4 Statistical diagram of the hysteresis loop of the Co-CoO single-layer amorphous-nanocrystalline exchange bias film prepared in Examples 1 to 4 of the present invention. Figure 3 and Figure 4 As shown in the figure, the exchange bias effect is present in Co-CoO amorphous-nanocrystalline films at substrate temperatures of 300K, 373K, 473K, and 573K, and the exchange bias field first increases and then decreases with increasing substrate temperature. The exchange bias field reaches its highest value of 5.29 kOe at a substrate temperature of 373K, indicating that the synergistic effect between the amorphous-nanocrystalline interface is optimal at this temperature.

[0064] The Co—CoO single-layer amorphous-nanocrystalline exchange bias film prepared in Example 2 was magnetically characterized using an MPMS-3 magnetic measurement system developed and produced by Quantum Design, Inc. in the United States. The sample was placed in the magnetic measurement system and evacuated. The temperature was lowered to 10 K at a cooling rate of 30 K / min under different cooling fields. The hysteresis loop was measured and the exchange bias field was calculated. The cooling fields selected for the test were 0.05 kOe, 0.1 kOe, 0.3 kOe, 0.5 kOe, 1 kOe, 5 kOe, 10 kOe, 30 kOe, and 50 kOe, respectively. Figure 5 This is a statistical diagram of the exchange bias field of the Co-CoO single-layer amorphous-nanocrystalline exchange bias film prepared in Example 2 of the present invention as a function of the cooling field. Figure 5 As shown in the figure, the exchange bias field of a Co-CoO monolayer amorphous-nanocrystalline film at a substrate temperature of 373K first increases and then decreases with increasing cooling field. A large exchange bias field of 4.54kOe is achieved at a small cooling field of 0.05kOe, and the exchange bias field reaches an optimal value of 5.29kOe at a cooling field of 10kOe. The cooling field of 10kOe can be regarded as the depinning threshold field. As the cooling field increases further, the antiferromagnetic region is insufficient to pin the ferromagnetic spins, resulting in a decrease in the exchange bias field.

[0065] The Co—CoO single-layer amorphous-nanocrystalline exchange bias films prepared in Examples 5 to 8 were magnetically characterized using an MPMS-3 magnetic measurement system developed and produced by Quantum Design, Inc., USA. The samples were placed in the magnetic measurement system and evacuated. Under the action of a 10 kOe cooling field, the temperature was lowered to 10 K at a cooling rate of 30 K / min, and then the hysteresis loops were measured. Figure 6 hysteresis loop diagram of the Co-CoO single-layer amorphous-nanocrystalline exchange bias film prepared in Examples 5 to 8 of the present invention, Figure 6 Among them, (a) is Example 5, (b) is Example 6, (c) is Example 7, and (d) is Example 8. Figure 6 As shown in the graph, when the sputtering power is 30W, 40W, 50W and 60W, the exchange bias effect exists in the prepared Co-CoO amorphous-nanocrystalline films, and the exchange bias fields are 1.5kOe, 1.08kOe, 0.86kOe and 0.69kOe, respectively.

[0066] It should be noted that when numerical ranges are mentioned in the present invention, it should be understood that both endpoints of each numerical range and any value between the two endpoints may be selected. Since the steps and methods used are the same as those in the embodiments, in order to avoid redundancy, the present invention describes preferred embodiments. Although preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they understand the basic inventive concepts. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0067] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

Claims

1. A method for preparing a Co-CoO single-layer amorphous-nanocrystalline exchange bias film, characterized in that: The following steps are involved: A substrate is provided; the substrate is heated at a heating temperature of 300K to 573K; and a Co-CoO single-layer amorphous-nanocrystalline exchange bias film is formed on the substrate by sputtering deposition using metal Co as a target by magnetron sputtering.

2. The method for preparing a Co-CoO single-layer amorphous-nanocrystalline exchange bias thin film according to claim 1, characterized in that: During the sputtering deposition process, a mixed gas containing reactive gas and protective gas is introduced, pre-sputtering is performed first, and then sputtering deposition is performed. The gas pressure of pre-sputtering is 2Pa~3Pa, the sputtering power is 20W~30W, and the sputtering gas pressure of sputtering deposition is 0.8Pa~1.4Pa, and the sputtering power is 20W~60W.

3. The method for preparing a Co-CoO single-layer amorphous-nanocrystalline exchange bias thin film according to claim 2, characterized in that: The mixed gas is oxygen and argon, and the oxygen partial pressure is 0.02%~0.5% of the total gas pressure of the mixed gas.

4. The method for preparing a Co-CoO single-layer amorphous-nanocrystalline exchange bias thin film according to claim 1, characterized in that: The sputtering deposition time is 10s to 1000s.

5. The method for preparing a Co-CoO single-layer amorphous-nanocrystalline exchange bias thin film according to claim 1, characterized in that: The vacuum degree during sputtering deposition is less than 2.5×10 -5 Pa.

6. The method for preparing a Co-CoO single-layer amorphous-nanocrystalline exchange bias thin film according to claim 1, characterized in that: The substrate is a wafer with crystal orientation or Si, Al2O3 or NaCl without crystal orientation.

7. The method for preparing a Co-CoO single-layer amorphous-nanocrystalline exchange bias thin film according to claim 1, characterized in that: Before use, the substrate was ultrasonically cleaned with acetone, ethanol and / or water in sequence.

8. The method for preparing a Co-CoO single-layer amorphous-nanocrystalline exchange bias thin film according to claim 1, characterized in that: The purity of metallic Co is ≥99.95%.

9. A Co-CoO single-layer amorphous-nanocrystalline exchange bias film, characterized in that: The preparation method is described in any one of claims 1 to 8.

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