Method for forming magnetic skyrmions based on femtosecond laser pulse control and writing device

Abstract

The application discloses a method for forming a magnetic skyrmion based on femtosecond laser pulse regulation and a writing device, and the method comprises the following steps: obtaining a CoFeB nanodisk and placing the CoFeB nanodisk in a sample placement area of a magneto-optical Kerr effect microscope; performing pulse excitation on the CoFeB nanodisk by adjusting a femtosecond laser thermal pulse, controlling the generation and annihilation of skyrmions of the CoFeB nanodisk in a preset area, and obtaining the number and position of the skyrmions; and performing data writing and reading according to the generation and annihilation of the skyrmions and the number and position of the skyrmions. The device comprises a femtosecond laser pulser, a CoFeB nanodisk and a temperature sensor. The embodiment of the application can reduce energy consumption, avoid the interference of external noise, and further improve the accurate control ability of the number and position of the skyrmions. The application can be widely applied in the technical field of spin electronics.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of spintronics, and in particular to a method for forming magnetic skyrmions based on femtosecond laser pulse regulation and a writing device. BACKGROUND

[0002] Skyrmions are a kind of spin structure with topological protection characteristics, which exhibit unique quasi-particle properties in magnetic materials. Due to the advantages of high stability, small size and insensitivity to external interference, skyrmions have broad application potential in high-density data storage, logic operation and brain-like computing devices. Spintronic devices based on skyrmions have significant advantages in power consumption, speed and density compared to traditional storage and computing devices, and thus have become a research hotspot in the fields of spintronics and nanotechnology. CoFeB (cobalt iron boron) is a kind of magnetic material widely used in the study of skyrmion characteristics. Its excellent perpendicular magnetic anisotropy and stability make the generation and control of skyrmions more efficient. However, the generation and stability of skyrmions are highly dependent on the thickness of the material layer, interface effects (such as Dzyaloshinskii-Moriya interaction, DMI effect) and other external excitations. However, the current methods for controlling skyrmions mainly include current injection and external magnetic field. However, these methods have the problem of high power consumption of current or magnetic field, and the movement or annihilation process of skyrmions is easily disturbed by external noise, making it difficult to achieve ideal control precision.

[0003] In summary, the technical problems in the related art need to be improved. SUMMARY

[0004] The main purpose of the embodiments of the present application is to provide a method for forming magnetic skyrmions based on femtosecond laser pulse regulation and a writing device, which can reduce energy consumption and avoid the interference of external noise, thereby improving the precision control ability of the number and position of skyrmions.

[0005] To achieve the above-mentioned purpose, one aspect of the embodiments of the present application provides a method for forming magnetic skyrmions based on femtosecond laser pulse regulation, which comprises the following steps:

[0006] Obtain a CoFeB nanodisk and place it in the sample placement area of a magneto-optical Kerr effect microscope;

[0007] Pulse excite the CoFeB nanodisk by adjusting the femtosecond laser thermal pulse, control the generation and annihilation of skyrmions in the CoFeB nanodisk in a predetermined area, and obtain the number and position of skyrmions;

[0008] According to the generation and annihilation of the skyrmions and the number and position of the skyrmions, data writing and reading are performed.

[0009] In some embodiments, the CoFeB nanodisk is pulsed excited by adjusting the femtosecond laser thermal pulse, the generation and annihilation of the skyrmions in the preset region of the CoFeB nanodisk are controlled, and the number and position of the skyrmions are obtained, including:

[0010] According to the preset thermal excitation condition, the femtosecond laser thermal pulse is adjusted;

[0011] According to the preset thermal excitation condition, the femtosecond laser thermal pulse is adjusted;

[0012] According to the generation and annihilation of the skyrmions, the number and position of the skyrmions are determined.

[0013] In some embodiments, the preset thermal excitation condition includes a pulse temperature range, a pulse duration and a pulse number, wherein:

[0014] The pulse temperature range is used to control the generation and annihilation of the skyrmions in the preset region of the CoFeB nanodisk;

[0015] The pulse duration and the pulse number are used to realize the response and control of the skyrmions in the preset region of the CoFeB nanodisk.

[0016] In some embodiments, the pulse temperature range includes a first preset pulse temperature range and a second preset pulse temperature range, the first preset pulse temperature range is greater than the second preset pulse temperature range, wherein:

[0017] The first preset pulse temperature range is used to control the generation of the skyrmions in the preset region of the CoFeB nanodisk;

[0018] The second preset pulse temperature range is used to control the annihilation of the skyrmions in the preset region of the CoFeB nanodisk.

[0019] In some embodiments, the femtosecond laser thermal pulse transmits heat to the preset region of the CoFeB nanodisk by an optical method, and the spatial range of the femtosecond laser thermal pulse is equal to the spatial range of the preset region of the CoFeB nanodisk.

[0020] In some embodiments, the data writing and reading are performed according to the generation and annihilation of the skyrmions and the number and position of the skyrmions, including:

[0021] writing data by the generation and annihilation of the skyrmions;

[0022] reading data by the number and position of the skyrmions.

[0023] To achieve the above object, another aspect of the embodiment of the present application proposes a magnetic skyrmion writing device based on femtosecond laser pulse control, which comprises a femtosecond laser pulse generator, a CoFeB nanodisk and a temperature sensor, the central axis of the femtosecond laser pulse generator is in line with the center of the CoFeB nanodisk, and the temperature sensor is connected to the CoFeB nanodisk in a non-contact manner, wherein:

[0024] The femtosecond laser pulse generator is used to emit a femtosecond laser thermal pulse;

[0025] The CoFeB nanodisk is used to control the generation and annihilation of skyrmions according to the femtosecond laser thermal pulse;

[0026] The temperature sensor is used to detect the temperature of the femtosecond laser thermal pulse.

[0027] In some embodiments, the femtosecond laser pulse generator comprises a femtosecond laser, a first lens, an aperture, a second lens, a polarizer, a third lens and an objective lens, the first lens, the aperture, the second lens, the polarizer, the third lens and the objective lens are placed in sequence along the direction of the femtosecond laser thermal pulse emitted by the femtosecond laser, wherein:

[0028] The femtosecond laser is used to generate the femtosecond laser thermal pulse;

[0029] The first lens is used to collimate and focus the femtosecond laser thermal pulse to obtain a focused femtosecond laser thermal pulse;

[0030] The aperture is used to adjust the cross-sectional diameter and shape of the focused femtosecond laser thermal pulse to obtain an adjusted femtosecond laser thermal pulse;

[0031] The second lens is used to optimize the beam energy density distribution of the adjusted femtosecond laser thermal pulse to obtain an optimized femtosecond laser thermal pulse;

[0032] The polarizer is used to filter the optimized femtosecond laser thermal pulse to obtain a filtered femtosecond laser thermal pulse;

[0033] The third lens is used to adjust the shape, diameter and optical axis direction of the filtered femtosecond laser thermal pulse to obtain an adjusted femtosecond laser thermal pulse;

[0034] The objective lens is used for converging the beam energy of the adjusted femtosecond laser thermal pulse to obtain a converged femtosecond laser thermal pulse.

[0035] In some embodiments, the CoFeB nanodisk includes a top layer, a free layer and a tunnel barrier layer, an upper surface of the free layer is covered by the top layer, and a lower surface of the free layer is covered by the tunnel barrier layer, wherein:

[0036] The top layer is used for generating electron spin polarization and optimizing magnetic anisotropy;

[0037] The free layer is used for forming and controlling magnetic skyrmions;

[0038] The tunnel barrier layer is used for enhancing electron spin polarization.

[0039] In some embodiments, the temperature sensor is an infrared temperature sensor, which detects the temperature of a preset region of the CoFeB nanodisk in a non-contact manner.

[0040] The embodiments of the present application at least have the following beneficial effects: the present application provides a magnetic skyrmion formation method and writing device based on femtosecond laser pulse regulation, which places the CoFeB nanodisk in the sample placement area of the magneto-optical Kerr effect microscope, and then adjusts the femtosecond laser thermal pulse to pulse excite the CoFeB nanodisk, controls the generation and annihilation of skyrmions in the CoFeB nanodisk in a preset region, adjusts the state and number of skyrmions in the CoFeB nanodisk through local femtosecond laser thermal pulse, can control the generation, annihilation and movement of skyrmions by changing the parameters of the femtosecond laser thermal pulse according to different application requirements, thereby reducing energy consumption, avoiding the interference of external noise, and improving the accurate control ability of the number and position of skyrmions. BRIEF DESCRIPTION OF DRAWINGS

[0041] Figure 1 is a flowchart of the magnetic skyrmion formation method based on femtosecond laser pulse regulation provided by the embodiments of the present application;

[0042] Figure 2 is a schematic diagram of initial skyrmions in the CoFeB nanodisk provided by the embodiments of the present application;

[0043] Figure 3 is a schematic diagram of the change of skyrmion configuration after the application of the femtosecond laser thermal pulse provided by the embodiments of the present application;

[0044] Figure 4 is a schematic diagram of the multi-layer film structure of the nanodisk provided by the embodiments of the present application;

[0045] Figure 5Figure 1 is a structural schematic diagram of a femtosecond laser pulse device provided by an embodiment of the present application.

[0046] Reference numeral 1, femtosecond laser; 2, first lens; 3, aperture; 4, second lens; 5, polarizer; 6, third lens; 7, objective lens; 8, nanodisk. DETAILED DESCRIPTION

[0047] In order to make the purposes, technical solutions and advantages of the present application clearer, the present application is further described in detail below in combination with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application. When the following description refers to the drawings, the same numbers in different drawings represent the same or similar elements unless otherwise indicated. The implementation described in the following exemplary embodiments does not represent all the implementations consistent with the embodiments of the present application, but is only an example of systems and methods consistent with some aspects of the embodiments of the present application as detailed in the appended claims.

[0048] It can be understood that the terms "first", "second", and the like used in the present application can be used herein to describe various concepts, but unless specifically stated, these concepts are not limited by these terms. These terms are only used to distinguish one concept from another. For example, without departing from the scope of the embodiments of the present application, the first information can also be referred to as the second information, and similarly, the second information can also be referred to as the first information. Depending on the context, the word "if" as used herein can be interpreted as "when" or "when" or "in response to determining".

[0049] The terms "at least one", "multiple", "each", "any" and the like used in the present application include one, two or more than two, multiple includes two or more than two, each refers to each of the corresponding multiple, and any refers to any one of the multiple.

[0050] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as understood by those skilled in the art to which the present application belongs. The terms used herein are only for the purpose of describing the embodiments of the present application and are not intended to limit the present application.

[0051] Reference Figure 1 , Figure 1 A flowchart of a method for forming magnetic skyrmions based on femtosecond laser pulse regulation provided by an embodiment of the present application is shown in Figure 2. Figure 1 The method comprises the following steps:

[0052] S100, obtaining a CoFeB nanodisk and placing it in the sample placement area of a magneto-optical Kerr effect microscope;

[0053] S200, controlling the generation and annihilation of the skyrmions in the preset region of the CoFeB nanodisk by adjusting the femtosecond laser thermal pulse to pulse excite the CoFeB nanodisk, and obtaining the number and position of the skyrmions;

[0054] In some embodiments, the step S200 can include: S210, adjusting the femtosecond laser thermal pulse according to the preset thermal excitation condition; S220, pulse exciting the preset region of the CoFeB nanodisk according to the adjusted femtosecond laser thermal pulse to control the generation and annihilation of the skyrmions in the preset region of the CoFeB nanodisk; S230, determining the number and position of the skyrmions according to the generation and annihilation of the skyrmions.

[0055] Further, it needs to be explained that in some specific embodiments, the preset thermal excitation condition includes a pulse temperature range, a pulse duration and a pulse number, wherein the pulse temperature range is used to control the generation and annihilation of the skyrmions in the preset region of the CoFeB nanodisk; the pulse duration and the pulse number are used to realize the response and control of the skyrmions in the preset region of the CoFeB nanodisk.

[0056] Wherein, the femtosecond laser thermal pulse generator is a laser heat source for transmitting heat to a specific region of the CoFeB nanodisk by optical method, the peak temperature range of the femtosecond laser thermal pulse is 300k to 2000k to adapt to the needs of different skyrmion generation and annihilation, the duration of the femtosecond laser thermal pulse is 10 picoseconds to realize the rapid response and accurate control of the skyrmions, and the spatial range of the local thermal pulse is the specific region of the CoFeB nanodisk to ensure the generation or annihilation of the skyrmions at the specified position.

[0057] Further, it also needs to be explained that the pulse temperature range includes a first preset pulse temperature range and a second preset pulse temperature range, the first preset pulse temperature range is greater than the second preset pulse temperature range, wherein the first preset pulse temperature range is used to control the generation of the skyrmions in the preset region of the CoFeB nanodisk; the second preset pulse temperature range is used to control the annihilation of the skyrmions in the preset region of the CoFeB nanodisk.

[0058] Wherein, the number and distribution of the skyrmions are controlled by adjusting the peak temperature and duration of the femtosecond laser thermal pulse. High temperature pulse (400k to 2000k) i.e. the first preset pulse temperature range is used to generate the skyrmions, and low temperature pulse (300k to 400k) i.e. the second preset pulse temperature range is used to annihilate the skyrmions.

[0059] S300, writing and reading data according to the generation and annihilation of the skyrmions and the number and position of the skyrmions;

[0060] It should be noted that in some embodiments, when writing data, heat pulses of different temperatures and durations are applied in the CoFeB nanodisk to change the generation or annihilation of skyrmions in a specific region, so as to adjust the distribution and number of skyrmions in the nanodisk; when reading data, the storage state is identified by detecting the number and position of skyrmions.

[0061] In summary, the embodiment of the application first selects a Ta / CoFeB / MgO multilayer film as a sample, further places the sample in a sample placement area of a magneto-optical Kerr effect microscope, as shown in Figure 2 The femtosecond laser pulse source is connected, and the output power, pulse frequency and duration of the laser are adjusted to generate controllable heating pulses, wherein the peak temperature and duration range of the laser are set to ensure that different temperatures and heating durations can be applied in the experiment. Specifically, the temperature range (from 300k to 2000K) of the femtosecond laser pulse is set by software. Different pulse durations are set to 10 picoseconds, and the pulse number is set to 50 times to simulate different thermal excitation conditions. After each pulse is applied, the changes in the number, shape and distribution of skyrmions are observed in real time, and all experimental parameters, including laser pulse conditions, skyrmion number, magnetic domain changes, etc., are recorded for subsequent data analysis. According to different application requirements, the generation, annihilation and movement of skyrmions are controlled by changing the parameters of the femtosecond laser heat pulse, as shown in Figure 3 The application mode and parameters of the femtosecond laser heat pulse can realize precise regulation of the skyrmion state in the CoFeB nanodisk.

[0062] The embodiment of the application also provides a magnetic skyrmion writing device based on femtosecond laser pulse regulation, which can realize the above-mentioned magnetic skyrmion formation method based on femtosecond laser pulse regulation. The device comprises a femtosecond laser pulse generator, a CoFeB nanodisk and a temperature sensor. The central axis of the femtosecond laser pulse generator is in the same straight line as the center of the CoFeB nanodisk. The temperature sensor is connected to the CoFeB nanodisk in a non-contact manner, wherein:

[0063] The femtosecond laser pulse generator is used to emit a femtosecond laser heat pulse;

[0064] Specifically, the femtosecond laser pulse generator comprises a femtosecond laser, a first lens, an aperture, a second lens, a polarizer, a third lens and an objective lens, the first lens, the aperture, the second lens, the polarizer, the third lens and the objective lens are sequentially arranged along the direction of the femtosecond laser thermal pulse emitted by the femtosecond laser, wherein the femtosecond laser is used to generate the femtosecond laser thermal pulse; the first lens is used to collimate and focus the femtosecond laser thermal pulse to obtain a focused femtosecond laser thermal pulse; the aperture is used to adjust the cross-sectional diameter and shape of the focused femtosecond laser thermal pulse to obtain an adjusted femtosecond laser thermal pulse; the second lens is used to optimize the beam energy density distribution of the adjusted femtosecond laser thermal pulse to obtain an optimized femtosecond laser thermal pulse; the polarizer is used to filter the optimized femtosecond laser thermal pulse to obtain a filtered femtosecond laser thermal pulse; the third lens is used to adjust the shape, diameter and optical axis direction of the filtered femtosecond laser thermal pulse to obtain an adjusted femtosecond laser thermal pulse; and the objective lens is used to converge the beam energy of the adjusted femtosecond laser thermal pulse to obtain a converged femtosecond laser thermal pulse.

[0065] In the embodiment, the femtosecond laser thermal pulse generator is used to apply a thermal pulse to a specific region in a CoFeB nanodisk of a Ta / CoFeB / MgO multilayer film structure; and the laser emitted by the femtosecond laser thermal pulse generator is emitted to the CoFeB nanodisk, and the temperature peak and duration of the thermal pulse are adjusted to control the number and state of the skyrmions.

[0066] More specifically, as shown in Figure 5 The femtosecond laser 1 is used to generate a femtosecond pulse light source. The pulse width of the light source is usually between tens of femtoseconds and hundreds of femtoseconds, which provides a light source with high peak power and high coherence, and is suitable for studying ultrafast dynamic processes and nonlinear optical effects. High transient energy density can instantaneously trigger material non-equilibrium processes such as electronic excitation, local heating, non-thermal electron dynamics, etc. The output light usually has a wide spectrum, and the center wavelength is in the near-infrared (such as 800 nm) or other ranges. The laser directly outputs pulse light, and the light beam is processed by subsequent optical systems, including spatial shaping, energy regulation, focusing, etc.

[0067] The first lens 2 is used to collimate or preliminarily focus the light beam output from the laser, to ensure the effective use of subsequent optical devices. If the light beam diverges, the lens can collimate the light beam to make it parallel. If it is necessary to adjust the spot size, the lens can preliminarily change the diameter of the light beam to optimize the subsequent energy distribution. The lens material needs to match the laser wavelength, and materials with high transmittance (such as fused quartz) are usually selected. The curvature radius and focal length are accurately selected according to the specific laser parameters and device design. The collimated or focused light beam enters the aperture for further screening of the light beam.

[0068] The aperture 3 is used to limit the spatial range of the light beam, control the cross-sectional diameter and shape of the light beam. Function: eliminate low-quality light at the edge of the laser beam, improve the uniformity of the light beam. Ensure that the size of the light beam matches the size of the subsequent optical elements (such as lenses and polarizers); the shape of the aperture (such as circular, square) can be selected according to the experimental requirements, and an adjustable aperture is often used to flexibly adjust the diameter.

[0069] The second lens 4 is used to further expand or focus the light beam after the aperture, and optimize the energy density distribution of the light beam. Change the diameter of the light beam to adjust the light intensity distribution. Modify the wavefront of the light beam to provide higher quality light for the action of the polarizer. Configure and design in cooperation with Lens 1, considering the overall optical path length and light beam shape requirements. The adjusted light beam is transmitted to the polarizer for polarization control.

[0070] The polarizer 5 is used to selectively filter the polarization state of the light beam, and optimize the polarization direction to adapt to the subsequent experimental requirements. Output linearly polarized light, and adjust the polarization direction to enhance the interaction effect of the laser and the material. Improve the directionality and coherence of the light beam, and reduce optical noise. The material of the polarizer is usually selected from high-transparency and high-polarization-selectivity materials (such as polarizing film or prism), and the position and angle need to be accurately adjusted to match the requirements of the objective lens and the sample. The adjusted polarized light beam is transmitted to the objective lens for final focusing.

[0071] The third lens 6 is used to adjust the light beam shape, diameter and optical axis direction, to ensure that the laser beam is uniformly and accurately transmitted to the objective lens, and to achieve the best focusing effect.

[0072] The objective lens 7 is used to focus the laser beam, and the light beam energy is concentrated on the target area (such as the surface of the nanodisk). Provide extremely high energy density, and the focused spot is usually smaller than microns, to achieve ultra-high spatial resolution energy transmission. Induce thermal effects, electron excitation or magnetic changes on the surface of the target material. High numerical aperture (NA) lenses are often used to achieve the smallest focused spot. The lens surface needs to have an anti-reflection coating to reduce the loss of laser energy. The focused laser directly acts on the target sample (nanodisk).

[0073] Nanodisk 8, select Ta / CoTeB / MgO multilayer film structure as the target material for laser action, study the physical processes of laser-induced thermal effects and magnetic regulation. Femtosecond laser generates local heating and ultrafast dynamic effects in a small area of the nanodisk. May trigger magnetic domain wall motion, formation or annihilation of Sgmin, and other complex magnetic changes.

[0074] CoFeB nanodisk is used to control the generation and annihilation of Sgmin according to the thermal pulse of femtosecond laser;

[0075] Specifically, the CoFeB nanodisk includes a top layer, a free layer, and a tunnel barrier layer, the upper surface of the free layer is covered with the top layer, and the lower surface of the free layer is covered with the tunnel barrier layer, wherein the top layer is used to generate electron spin polarization and optimize magnetic anisotropy; the free layer is used to form and control magnetic skyrmions; and the tunnel barrier layer is used to enhance electron spin polarization.

[0076] In the embodiment, as shown in Figure 4 The top layer Ta is used as a protective layer to prevent the CoFeB layer from oxidizing and enhance the structural stability due to its high stability and oxidation resistance. Tantalum plays a key role in the interface quality between the magnetic layer (such as CoFeB) and the non-magnetic layer, optimizing the magnetic properties such as spin polarization and magnetic anisotropy.

[0077] The intermediate layer, CoFeB (cobalt iron boron), is the free layer, which is used to form and control magnetic skyrmions. Its magnetic properties can be precisely adjusted by external stimuli (such as laser, temperature field). It has high saturation magnetization (Ms) and low magnetic anisotropy, making it suitable for use as a working layer in nanomagnetic devices. CoFeB is a magnetic material commonly used in spintronic MRAM, which can support the transmission of spin-polarized current. By adjusting the thickness or interface quality, the anisotropy of the magnetic layer can be controlled, thereby affecting the stability of the magnetic state. CoFeB is sensitive to femtosecond laser-induced thermal effects, making it an ideal material for studying temperature-regulated magnetic properties. The CoFeB / MgO interface can generate strong interface DMI, which is beneficial to the formation of stable skyrmion nanostructures, i.e., the magnetic material is a CoFeB thin film with perpendicular magnetic anisotropy, which supports the formation and control of skyrmions through its spin structure properties.

[0078] The bottom layer, MgO (magnesium oxide), serves as a tunnel barrier layer, providing an enhancement of interface electron spin polarization for magnetic tunnel junctions (MTJ). In addition, it supports perpendicular magnetic anisotropy (PMA), stabilizing the formation of skyrmions. It is an electrical insulator with high thermal stability and can be well matched with CoFeB to form an interface effect.

[0079] The temperature sensor is used to detect the temperature of the femtosecond laser thermal pulse.

[0080] The temperature sensor is an infrared temperature sensor that detects the temperature of a predetermined area of the CoFeB nanodisk in a non-contact manner.

[0081] In the embodiment, the temperature sensor is placed in the vicinity of the CoFeB nanodisk to monitor the temperature of the femtosecond laser thermal pulse area in real time, ensuring the stability and control accuracy of the skyrmions.

[0082] To sum up, the Ta / CoFeB / MgO film in the embodiment of the application is deposited on a substrate by a magnetron sputtering technology. During the sputtering process, parameters such as atmosphere, temperature and power are controlled to make the film have perpendicular magnetic anisotropy so as to support the formation of a SQUID. After the film deposition is completed, the CoFeB film is patterned by using an electron beam lithography technology, and then an ion beam etching is performed to form a disc structure with a diameter of 100 nanometers to 1 micrometer, so as to ensure the structure precision. After the disc structure is prepared, a thermal pulse control device is installed in place. The device includes a laser heat source and a temperature monitoring module. The laser is used to generate a local thermal pulse, and the temperature sensor is used for real-time monitoring to ensure the stability of the temperature.

[0083] It can be understood that the content in the method embodiment is applicable to the system embodiment, the system embodiment specifically implements the same functions as the method embodiment, and achieves the same beneficial effects as the method embodiment.

[0084] The preferred embodiments of the application are described above with reference to the drawings, and the scope of the application is not limited by this. Any modification, equivalent replacement and improvement made by those skilled in the art without departing from the scope and essence of the application should be within the scope of the application.

Claims

1. A method for forming magnetic skyrmions based on femtosecond laser pulse control, characterized in that, The method comprises the following steps: Obtaining a CoFeB nanodisk and placing it in a sample placement area of a magneto-optical Kerr effect microscope; the CoFeB nanodisk comprises a top layer, a free layer and a tunnel barrier layer, the upper surface of the free layer is covered with the top layer, and the lower surface of the free layer is covered with the tunnel barrier layer; the free layer is made of CoFeB, and the magnetic properties of the free layer are adjusted by external stimulation; Controlling the generation and annihilation of skyrmions in the CoFeB nanodisk in a preset area by adjusting the femtosecond laser thermal pulse to pulse excite the CoFeB nanodisk, and obtaining the number and position of the skyrmions; According to the generation and annihilation of the skyrmions and the number and position of the skyrmions, data writing and reading are performed; Wherein, the femtosecond laser thermal pulse is adjusted according to the preset thermal excitation condition; the preset thermal excitation condition includes pulse temperature range, pulse duration and pulse number; the pulse temperature range is 300k to 2000k; According to the preset area of the CoFeB nanodisk, the pulse excitation is performed by adjusting the femtosecond laser thermal pulse, and the generation and annihilation of skyrmions in the CoFeB nanodisk in the preset area are controlled; According to the generation and annihilation of the skyrmions, the number and position of the skyrmions are determined. The pulse temperature range is used to control the generation and annihilation of skyrmions in the CoFeB nanodisk in the preset area; 2. The method of claim 1, wherein, The pulse duration and the pulse number are used to realize the response and control of the skyrmions in the CoFeB nanodisk in the preset area. The pulse temperature range includes a first preset pulse temperature range and a second preset pulse temperature range, the first preset pulse temperature range is greater than the second preset pulse temperature range, wherein:

3. The method of claim 2, wherein, The first preset pulse temperature range is used to control the generation of skyrmions in the CoFeB nanodisk in the preset area; The second preset pulse temperature range is used to control the annihilation of skyrmions in the CoFeB nanodisk in the preset area. The femtosecond laser thermal pulse transmits heat to the preset area of the CoFeB nanodisk by optical method, and the spatial range of the femtosecond laser thermal pulse is equal to the spatial range of the preset area of the CoFeB nanodisk.

4. The method of claim 1, wherein, According to the generation and annihilation of the skyrmions and the number and position of the skyrmions, data writing and reading are performed, comprising:

5. The method of claim 1, wherein, Data writing is performed by the generation and annihilation of the skyrmions; Data reading is performed by the number and position of the skyrmions. ​ 6. A device for writing magnetic skyrmions based on femtosecond laser pulse control, characterized in that, The writing device is applied to the forming method in any one of claims 1-5, and the device comprises a femtosecond laser pulser, a CoFeB nanodisk and a temperature sensor, a central axis of the femtosecond laser pulser is in a same straight line with a center of the CoFeB nanodisk, and the temperature sensor is connected with the CoFeB nanodisk in a non-contact manner, wherein: The femtosecond laser pulser is used for emitting a femtosecond laser thermal pulse. The CoFeB nanodisk is used for controlling generation and annihilation of a skyrmion according to the femtosecond laser thermal pulse. The temperature sensor is used for detecting a temperature of the femtosecond laser thermal pulse.

7. The apparatus of claim 6, wherein, The femtosecond laser pulser comprises a femtosecond laser, a first lens, an aperture, a second lens, a polarizer, a third lens and an objective lens, the first lens, the aperture, the second lens, the polarizer, the third lens and the objective lens are placed in sequence along a direction of a femtosecond laser thermal pulse emitted by the femtosecond laser, wherein: The femtosecond laser is used for generating the femtosecond laser thermal pulse. The first lens is used for collimating and focusing the femtosecond laser thermal pulse to obtain a focused femtosecond laser thermal pulse. The aperture is used for adjusting a cross-sectional diameter and shape of the focused femtosecond laser thermal pulse to obtain an adjusted femtosecond laser thermal pulse. The second lens is used for optimizing a beam energy density distribution of the adjusted femtosecond laser thermal pulse to obtain an optimized femtosecond laser thermal pulse. The polarizer is used for filtering the optimized femtosecond laser thermal pulse to obtain a filtered femtosecond laser thermal pulse. The third lens is used for adjusting a shape, a diameter and an optical axis direction of the filtered femtosecond laser thermal pulse to obtain an adjusted femtosecond laser thermal pulse. The objective lens is used for converging a beam energy of the adjusted femtosecond laser thermal pulse to obtain a converged femtosecond laser thermal pulse.

8. The apparatus of claim 6, wherein, The top layer is used for generating electron spin polarization and optimizing magnetic anisotropy. The free layer is used for forming and controlling a magnetic skyrmion. The tunnel barrier layer is used for enhancing electron spin polarization.

9. The apparatus of claim 6, wherein, The temperature sensor is an infrared temperature sensor, and the temperature sensor detects a temperature of a preset region of the CoFeB nanodisk in a non-contact manner.

Images