Perpendicular magnetic anisotropy energy regulation and control method and application

Abstract

The invention discloses a vertical magnetic anisotropy energy regulation and control method and application, and the method comprises the steps: simulating sunlight with different illumination frequencies through employing simulated sunlight and adjusting the distance from a light source to a metal film and the current of the light source; depositing a plurality of layers of metal films on a pre-cleaned substrate to form a ferromagnetic heterogeneous film; simulated sunlight is vertically incident on the ferromagnetic heterogeneous film, then a magnetic field perpendicular to the surface of the sample is applied, and the magnetism of the ferromagnetic heterogeneous film is regulated and controlled by changing the sizes of the applied magnetic field and the simulated sunlight field. According to the invention, the energy consumption is reduced, and the PN Si which is easy to integrate has higher photovoltaic conversion efficiency and chemical stability than an organic photovoltaic composite material.

Description

Technical Field

[0001] The present invention belongs to the technical field of magnetic materials, and particularly relates to a method for regulating perpendicular magnetic anisotropy energy and its application. Background Art

[0002] Manipulating ferromagnetism at low power is crucial for spintronic devices, such as magnetic random access memories (MRAMs). Spin-polarized currents, originating from spin-transfer torque (STT) in spin valves and magnetic tunnel junctions (MTJs), or spin-orbit torque (SOT) at ferromagnetic (FM) / heavy-metal (HM) interfaces, are widely used to achieve deterministic magnetization switching, ultrafast ferromagnetic domain wall motion, and gigahertz ferromagnetic oscillations in various ferromagnetic heterojunctions. Considerable efforts have been made by researchers to develop new spin-polarized current generators, such as two-dimensional materials, topological insulators, etc., and optimize their interfaces to increase the rate of charge conversion to spin and reduce energy consumption. However, the relatively high current density generates local heating problems and limits the storage density and magnetization switching speed. Summary of the Invention

[0003] The purpose of the present invention is to provide a method for regulating perpendicular magnetic anisotropy energy and its application to solve the above problems.

[0004] To achieve the above purpose, the present invention adopts the following technical solutions: A method for regulating perpendicular magnetic anisotropy energy, comprising: Using simulated sunlight, and simulating sunlight with different illumination frequencies by adjusting the distance between the light source and the metal film and the magnitude of the current of the light source; Depositing a multi-layer metal film on a pre-cleaned substrate to form a ferromagnetic heterostructure film; Vertically irradiating the simulated sunlight onto the ferromagnetic heterostructure film, and then applying a magnetic field perpendicular to the surface of the sample, and regulating the magnetism of the ferromagnetic heterostructure film by changing the magnitudes of the applied magnetic field and the simulated sunlight optical field.

[0005] Further, a xenon lamp solar simulator is used to simulate sunlight.

[0006] Further, the device is illuminated with AM1.5G and a light intensity of 100 mW / cm² using a xenon lamp solar simulator.

[0007] Further, the depositing the multi-layer metal film on a pre-cleaned substrate includes: Selecting a Pt / Co / Pt three-layer film and depositing it on a pre-cleaned PN-Si substrate in sequence.

[0008] Further, the specific deposition process is: Substrate preparation: Prepare a single-crystalline silicon substrate and perform pre-cleaning to ensure its surface is clean and smooth; Loading the substrate: Mount the single-crystalline silicon substrate onto the sample holder of the thin-film deposition system; Vacuum pumping by the vacuum pump: Start the vacuum pump of the deposition system and pump the system to a high-vacuum state; Deposition of the bottom-layer thin film: Deposit the first metal Pt layer to ensure the thin film uniformly covers the entire surface of the substrate; Deposition of the intermediate-layer thin film: Deposit a Co thin film on the first metal Pt layer; Deposition of the top-layer thin film: Deposit the second metal Pt layer on the Co thin film to form a multi-layer thin-film structure.

[0009] Furthermore, the pre-cleaning of the single-crystalline silicon substrate includes: completely immersing the substrate in acetone with a concentration of 99% and cleaning it in an ultrasonic oscillator at a power of 85 - 95 w for 9 - 12 min; then completely immersing it in alcohol with a concentration of 99% and cleaning it in an ultrasonic oscillator at a power of 85 - 95 w for 9 - 12 min; finally, completely immersing it in deionized water and cleaning it in an ultrasonic oscillator at a power of 85 - 95 w for 9 - 12 min, and drying it with an air gun.

[0010] Furthermore, the thickness of the first metal Pt layer is 0.5 - 3.0 nm respectively. When depositing, set the sputtering power to 10 - 200 w and the working gas pressure to 3 mT.

[0011] Furthermore, the thickness of the Co thin film is 0.5 - 1.2 nm. When depositing, set the sputtering power to 10 - 200 w and the working gas pressure to 3 - 10 mT.

[0012] Furthermore, the thickness of the second metal Pt layer is 1.0 - 5.0 nm. When depositing, set the sputtering power to 30 - 200 w and the working gas pressure to 3 mT. An application of a method for regulating perpendicular magnetic anisotropy energy for regulating the current or voltage of a photovoltaic spintronic device.

[0013] Compared with the prior art, the present invention has the following technical effects: The object of the present invention is to provide a method for manipulating the magnetic change of a low-power natural light field in a Pt / Co / Pt trilayer ferromagnetic thin film. This method is energy-saving: Generally, spins are regulated by spin-polarized currents or voltages in different ferromagnetic heterostructures, but their energy consumption is relatively high. This design proposes an energy-saving structure for sunlight-regulated perpendicular magnetic anisotropy based on a Pt(0.8 nm) / Co(0.65 nm) / Pt(2.5 nm) / PN Si heterojunction. Under sunlight illumination, the coercivity decreases from 261 Oe to 95 Oe (a change amplitude of 64%). Combined with a magnetic bias of 140 Oe, a nearly 180-degree deterministic reversible magnetization reversal is achieved. Photoelectrons induce a redistribution of the orbital magnetic moment and spin magnetic moment during the Co magnetization process. By changing the Fermi level position, it enhances the in-plane spin-orbit coupling effect field at the Co / Pt interface, resulting in a weakening of the perpendicular magnetic anisotropy, a decrease in coercivity, and the corresponding magnetization reversal, thereby reducing the Joule heat generated by high switching currents. In this experiment, we achieved a nearly 180° magnetization switching in the Pt / Co / Pt / PN Si heterostructure under the assistance of a magnetic field under simulated sunlight illumination. Pt / Co / Pt is selected because it has perpendicular magnetic anisotropy and is widely used in magnetic storage due to its high storage density. At the same time, the easily integrated PN Si has a higher photovoltaic conversion efficiency and chemical stability than organic photovoltaic composite materials. Description of the Drawings

[0014] Figure 1 Hysteresis loops in the Pt (0.8 nm) / Co (0.65 nm) / Pt (2.5 nm) / PN Si heterostructure in the on and off states of the light Figure 2 In a, the Hc of the Pt (0.8 nm) / Co (x nm) / Pt (2.75 nm) / PN Si sample depends on the Co thickness. Here, x represents the Co thickness; in b, the Hc of the Pt (0.8 nm) / Co (0.65 nm) / Pt (y nm) / PN-Si sample depends on the Pt thickness. Here, y represents the Pt thickness. Detailed Embodiment

[0015] The present invention will be further described below in conjunction with the drawings.

[0016] Embodiment 1. The present invention provides a method for regulating the perpendicular magnetic anisotropy energy, including: Using simulated sunlight, by adjusting the distance from the light source to the metal thin film and the current magnitude of the light source, simulate sunlight with different illumination frequencies; Deposit a multilayer metal thin film on a pre-cleaned substrate to form a ferromagnetic heterostructure thin film; Vertically irradiate simulated sunlight onto the ferromagnetic heterostructure thin film, and then apply a magnetic field perpendicular to the sample surface to control the magnetism of the ferromagnetic heterostructure thin film by changing the magnitudes of the applied magnetic field and the simulated sunlight optical field.

[0017] Example 2. The present invention provides a method for controlling perpendicular magnetic anisotropy energy, and the method comprises the following steps: S1. Preparation of the thin film: Deposit a multilayer thin film with a Pt / Co / Pt structure on a pre-cleaned PN-Si substrate, with the base vacuum degree lower than 1×10-7 Torr, and no further in-situ annealing treatment is performed; S2. Preparation of the simulated light source in the control system: Use a xenon lamp solar simulator to simulate sunlight, and adjust the size of the light source by adjusting the distance between the light source and the thin film and the current magnitude of the light source to simulate sunlight with different illumination frequencies.

[0018] S3. Control the magnetism of the metal thin film: Control the magnetism of the metal thin film by changing the light power magnitude of the xenon lamp solar simulator.

[0019] In the method as described above, in step S1, the substrate is: a Si substrate with a size of 5mm*5mm and a square shape.

[0020] In the method as described above, in step S1, the thin film structure is: Pt (0.8 nm) / Co (0.65nm) / Pt (2.5nm).

[0021] In the method as described above, in step S1, the substrate used needs to be completely immersed in acetone with a concentration of 99% and cleaned in an ultrasonic oscillator at a power of 90w for 10min; then completely immersed in alcohol with a concentration of 99% and cleaned in an ultrasonic oscillator at a power of 90w for 10min; finally, completely immersed in deionized water and cleaned in an ultrasonic oscillator at a power of 90w for 10min and dried with an air gun to ensure the cleanliness of the substrate.

[0022] In the method as described above, in step S1, when depositing a 0.8nm Pt film, set the sputtering power to 20w, the working gas pressure to 3mT, and the sputtering time to 25s.

[0023] In the method as described above, in step S1, when depositing a 0.65nm Co film, set the sputtering power to 30w, the working gas pressure to 3mT, and the sputtering time to 90s.

[0024] In the method as described above, in step S1, when depositing a 2.5nm Pt film, set the sputtering power to 20w, the working gas pressure to 3mT, and the sputtering time to 78s.

[0025] For the method described above, in step S3, under the condition that the thin film is not affected by external light sources after the light source is applied, magnetic testing is performed to confirm the regulation effect.

[0026] Specific implementation method: Preparation and characterization of photovoltaic spintronic devices: A PN-Si wafer was used as the light absorption medium. By using magnetron sputtering, a multilayer film with a Pt / Co / Pt structure was deposited on the pre-cleaned PN-Si wafer at room temperature, and the base pressure was below 1×10-7 Torr. No further in-situ annealing was performed. The sunlight-dependent measurement of the optical hysteresis loop was carried out by using a vibrating sample magnetometer (Lakeshore 7400). Under a PL-XQ500W xenon lamp solar simulator, the test was performed at an irradiation intensity of AM1.5G (100mW / cm 2 ).

[0027] In-situ measurement of magnetic properties: In-situ magnetic anisotropy modification was carried out in a VSM (Lakeshore 7404) and an ESR spectrometer (JES-FA200, JEOL RESONANCE Inc.). The rotator could show the angle between the film plane and the applied magnetic field. The microwave power of the TE011 mode provided by the microwave unit was 9200 MHz. Under a PL-XQ500W xenon lamp solar simulator, the test was performed at an irradiation intensity of AM1.5G (100 mW / cm 2 ). The standard sunlight irradiation intensity was 100 mW / cm 2 (1 sun).

[0028] XMCD measurement: XMCD measurement was carried out on the "XMCD-A" beamline of the National Synchrotron Radiation Laboratory (NSRL) in China. The "XMCD-A" experimental station was equipped with an octupole vector electromagnet that could apply a magnetic field of 0 to 8000 Oe in any direction. The intensity of the X-ray absorption spectrum (XAS) was recorded in the total electron yield mode at the Co edge. In the XMCD measurement, a magnetic field of 1000 Oe was applied along the normal direction of the sample, which was sufficient to magnetize the Co layer in the sample to saturation. All XMCD measurements were performed at room temperature.

[0029] Implementation steps: (1) Substrate preparation: Prepare a single-crystalline silicon (Si) substrate to ensure that its surface is clean and smooth. This will be the growth substrate for the multilayer film.

[0030] (2) Loading the substrate: Mount the Si substrate on the sample holder of the thin film deposition system to ensure that it can be exposed to the deposition environment.

[0031] (3) Vacuum pumping by the vacuum pump: Start the vacuum pump of the deposition system and pump the system to a high vacuum state. (4)Bottom film deposition: Deposit the first metal Pt layer. Before deposition, set the deposition parameters. Set the sputtering power to 20 w, the working gas pressure to 3 mT, and the sputtering time to 25 s. Ensure that the film uniformly covers the entire substrate surface.

[0032] (5)Intermediate layer film deposition: Deposit the Co film. Set the sputtering power to 20 w, the working gas pressure to 3 mT, and the sputtering time to 78 s. To ensure the required film structure.

[0033] (6)Top layer film deposition: Deposit the second metal layer (Pt) to complete the multi-layer film structure. Set the sputtering power to 20 w, the working gas pressure to 3 mT, and the sputtering time to 78 s.

[0034] (7)Set the light parameters: Use the control panel of the simulator to set the light parameters. In this experiment, the light intensity is set to AM1.5G (100 mW / cm 2 ).

[0035] (8)Adjust the sample position: Place the sample holder and the multi-layer film in a suitable position to ensure that the sample is perpendicular to the light source.

[0036] (9)According to the experimental content, the ferromagnetic films were irradiated with light of different times and intensities, and then the irradiated ferromagnetic films were tested. First, elemental-resolved X-ray absorption spectroscopy (XAS) and XMCD measurements were performed to reveal the effects of sunlight irradiation on the chemical state and intrinsic ferromagnetism of the PMA heterostructure, and then VSM tests were carried out.

[0037] Under sunlight irradiation, the hysteresis loop (M-H loop) was measured by a vibrating sample magnetometer (VSM). When the thickness and composition of the three-layer film were Pt (0.8 nm) / Co (0.65 nm) / Pt (2.5 nm), the maximum magnetic field strength change (-156 Oe) was achieved. The external magnetic field was applied along the direction perpendicular to the film plane. As Figure 1 shown.

[0038] The control experiment is as Figure 2 shown, to find the optimal thickness of the Co and Pt nanolayers, Figure 2 shown the sunlight-induced tunability of different Co and Pt thicknesses, where under 1 sun illumination, the maximum Hc shift of -156 Oe was obtained with 0.65 nm of Co and 2.5 nm of Pt.

[0039] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: it is still possible to modify the specific implementation manners of the present invention or make equivalent replacements, and any modification or equivalent replacement that does not depart from the spirit and scope of the present invention shall be covered by the protection scope of the claims of the present invention.

Claims

1. A method for regulating perpendicular magnetic anisotropy energy, characterized in that, Including: Using simulated sunlight, by adjusting the distance from the light source to the metal thin film and the current magnitude of the light source, to simulate sunlight with different illumination frequencies; Depositing a multi-layer metal thin film on a pre-cleaned substrate to form a ferromagnetic hetero-thin film; Vertically incident the simulated sunlight on the ferromagnetic hetero-thin film, then apply a magnetic field perpendicular to the sample surface, and regulate the magnetism of the ferromagnetic hetero-thin film by changing the magnitudes of the applied magnetic field and the simulated sunlight optical field.

2. A method for controlling perpendicular magnetic anisotropy energy according to claim 1, characterized in that, Using a xenon lamp solar simulator to simulate sunlight.

3. A method for regulating perpendicular magnetic anisotropy energy according to claim 1, characterized in that Using a xenon lamp solar simulator to illuminate the device with AM1.5G and a light intensity of 100 mW / cm².

4. A method for regulating perpendicular magnetic anisotropy energy according to claim 1, characterized in that The depositing the multi-layer metal thin film on a pre-cleaned substrate includes: Selecting a Pt / Co / Pt three-layer film and depositing it sequentially on a pre-cleaned PN-Si substrate.

5. A method for regulating perpendicular magnetic anisotropy energy according to claim 4, characterized in that The specific deposition process is as follows: Substrate preparation: Prepare a single-crystalline silicon substrate, perform pre-cleaning to ensure its surface is clean and smooth; Loading the substrate: Mount the single-crystalline silicon substrate on the sample holder of the thin film deposition system; Vacuum pump evacuation: Start the vacuum pump of the deposition system and evacuate the system to a high vacuum state; Depositing the bottom thin film: Deposit the first metal Pt layer to ensure the thin film uniformly covers the entire substrate surface; Depositing the intermediate thin film: Deposit a Co thin film on the first metal Pt layer; Depositing the top thin film: Deposit the second metal Pt layer on the Co thin film to form a multi-layer thin film structure.

6. A method for regulating perpendicular magnetic anisotropy energy according to claim 5, characterized in that, The pre-cleaning of the single-crystalline silicon substrate includes: Completely immerse the substrate in acetone with a concentration of 99% and clean it in an ultrasonic oscillator at a power of 85 - 95 w for 9 - 12 min; then completely immerse it in alcohol with a concentration of 99% and clean it in an ultrasonic oscillator at a power of 85 - 95 w for 9 - 12 min; finally, completely immerse it in deionized water and clean it in an ultrasonic oscillator at a power of 85 - 95 w for 9 - 12 min, and dry it with an air gun.

7. A method for regulating perpendicular magnetic anisotropy energy according to claim 5, characterized in that, The thickness of the first metal Pt layer is 0.5 - 3.0 nm, and when depositing, set the sputtering power to 10 - 200 w and the working gas pressure to 3 mT.

8. A method for regulating perpendicular magnetic anisotropy energy according to claim 5, characterized in that The thickness of the Co thin film is 0.5 - 1.2 nm, and when depositing, set the sputtering power to 10 - 200 w and the working gas pressure to 3 - 10 mT.

9. A method for regulating perpendicular magnetic anisotropy energy according to claim 5, characterized in that The thickness of the second metal Pt layer is 1.0 - 5.0 nm, and when depositing, set the sputtering power to 30 - 200 w and the working gas pressure to 3 mT.

10. Application of a method for regulating perpendicular magnetic anisotropy energy, characterized in that, A method for regulating perpendicular magnetic anisotropy energy according to any one of claims 1 to 9, for regulating the current or voltage of a photovoltaic spintronic device.

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