CN108535671B - A method for measuring magnetization dynamics at the nanoscale - Google Patents

Abstract

The invention relates to the field of material surface magnetism measurement, in particular to a method for measuring nanoscale magnetization dynamics, wherein a measuring device comprises a pulse laser, a time delay device, an 1/4 wave plate, a concave lens, a convex lens I, a plane mirror, a polaroid, a beam splitter, a convex lens II, a lens platform, an atomic force microscope I, a probe I, a lens seat, an objective lens, a sample, a waveguide, a sample platform, a signal generator, an oscilloscope, a detector, a bias tee joint, an amplifier I, a mixer, an amplifier II, an analog-to-digital converter, a computer, an atomic force microscope II, a probe II and a phase sensitive detector, can measure a single nanostructure, can achieve submicron-order spatial resolution for measuring the magnetization dynamics of the surface of the sample, and adopts two different atomic force microscope tips to respectively carry out contact-mode atomic force microscope scanning and near-field time resolution magneto-optic effect experiments, and a frequency domain method is adopted to detect the magnetization dynamics of a GHz frequency band on the surface of the sample, so that the method has high sensitivity.

Description

A method for measuring magnetization dynamics at the nanoscale

technical field

The invention relates to the field of material surface magnetic measurement, in particular to a nanoscale magnetization dynamic measurement method capable of measuring the high-frequency dynamic magnetization of a single nanostructure on the material surface.

Background technique

The magneto-optical Kerr effect measurement device is an important method in the study of material surface magnetism. Its working principle is based on the magneto-optical Kerr effect caused by the interaction between light and magnetized media. It has important applications in the study of magnetic order, magnetic anisotropy, interlayer coupling and phase transition behavior of magnetic ultra-thin films. The magneto-optical Kerr effect measurement device mainly observes the magnetization of the sample surface by detecting the light intensity change caused by the polarization state change of a beam of linearly polarized light reflected on the material surface. There are technical defects 1: the spatial resolution of the traditional focusing Kerr microscope using microscope objective is determined by the optical diffraction limit, so the dynamic characteristics of magnetization at the nanoscale cannot be obtained; The magnetization dynamic information, the method for measuring the nano-scale magnetization dynamic can solve the problem.

SUMMARY OF THE INVENTION

In order to solve the above problems, the present invention provides a method for measuring the nanoscale magnetization dynamics. The measuring device adopts a high-precision positioning device to obtain the magnetization information of the nanoscale sample surface, and adopts the frequency domain method to detect the magnetization dynamics of the sample surface in the GHz frequency band. .

The technical scheme adopted in the present invention is:

The measuring device mainly includes pulsed laser, delay device, 1/4 wave plate, concave lens, convex lens I, plane mirror, polarizer, beam splitter, convex lens II, lens stage, atomic force microscope I, probe I, lens holder, objective lens, Sample, Waveguide, Sample Stage, Signal Generator, Oscilloscope, Optical Bridge Detector, Bias Tee, Amplifier I, Mixer, Amplifier II, A/D Converter, Computer, AFM II, Probe II, Phase Sensitive Detector, sinusoidal signal generator, incident light path and reflected light path, the input end of the optical bridge detector has a polarizer with an angle of 45 degrees, the atomic force microscope II has the same structure as the atomic force microscope I, and the probe I is located at The lower end of the atomic force microscope I, the probe II is located at the lower end of the atomic force microscope II, the objective lens is located at the lower end of the lens holder, the pulsed laser, the signal generator, the waveguide, and the oscilloscope are connected by cables in sequence, and the optical bridge detector, offset three Amplifier I, mixer, amplifier II, analog-to-digital converter, and computer are connected with cables in sequence, and the laser beam emitted by the pulsed laser passes through the delay device, 1/4 wave plate, concave lens, convex lens I, plane mirror, polarization Sheet, beam splitter, convex lens II, lens stage, atomic force microscope I, probe I, thereby forming an incident light path, and the reflected light generated by the laser beam irradiating the surface of the sample passes through probe I, atomic force microscope I, lens stage, Convex lens II, beam splitter, thus forming a reflected light path, the reflected light is deflected by the beam splitter to the optical bridge detector, the lens stage is a light-transmitting disk and has a central axis, the atomic force microscope I, lens The seat and AFM II are located under the lens stage respectively, and can be fine-tuned relative to the position of the lens stage. When the lens stage is rotated around its central axis, the AFM I or the lens seat or AFM II can be placed on the sample (15) ) directly above, the probe II is a contact-type atomic force microscope probe, the waveguide is located on the sample stage, and the sample is directly contacted on the upper surface of the waveguide by the magnetron sputtering method, and the probe I and probe II are The atomic force microscope probes of the same external dimensions have a circular truncated shape, the axis of the truncated truncated cone is perpendicular to the horizontal plane, and the probe I has a truncated truncated through hole; The diameter of the upper bottom surface is 3 micrometers, the diameter of the lower bottom surface is 2 micrometers, the diameter of the upper opening of the frustum-shaped through hole in the probe 1 is 500 nanometers, the diameter of the lower opening is 900 nanometers, and the diameter of the lens stage is ten centimeters ; The waveguide length is 80 microns, the width is 50 microns, the thickness is 150 nanometers, and the characteristic impedance is 50 ohms; the sample length is 10 microns, the width is 9 microns, and the thickness is 50 nanometers.

其中I₀是反射光到达所述偏振器时的光强，θ_k是克尔角。所述混频器具有输入端I和输入端II的两个信号输入端。当反射光强对样品磁化的依赖关系是线性的，能够估计光桥探测器中的由样品磁化导致的电流的交流分量δI≈I_DCθ_K0δm_z，其中θ_K0是样品在磁化饱和条件下的克尔角，δm_z是面外磁化的变化，I_DC是光桥探测器中的电流的直流分量。The output end of the optical bridge detector is connected to the input end of a phase sensitive detector, the reference frequency of the phase sensitive detector is set to be consistent with the output frequency of the signal generator, and the output end of the phase sensitive detector is connected to the offset three. The output terminal of the sine signal generator is connected to the input terminal II of the mixer. The input end of the optical bridge detector has a polarizer with an angle of 45 degrees. After the reflected light passes through the polarizer, the light intensity is

where I ₀ is the light intensity of the reflected light when it reaches the polarizer, and θ _k is the Kerr angle. The mixer has two signal inputs, input I and input II. When the dependence of the reflected light intensity on the sample magnetization is linear, it is possible to estimate the AC component of the current in the optical bridge detector caused by the sample magnetization δI≈I _DC θ _K0 δm _z , where θ _K0 is the sample at the magnetization saturation condition The Kerr angle, δm _z is the change in out-of-plane magnetization, and I _DC is the DC component of the current in the optical bridge detector.

The measurement device uses a high-precision positioning device to obtain the magnetization information of the nanoscale sample surface, that is, two different atomic force microscope tips are used to conduct contact mode atomic force microscope scanning and near-field time-resolved magneto-optical Kerr effect experiments, and use frequency domain. The method to detect the magnetization dynamics of the sample surface in the GHz frequency band has the advantages of higher spatial sensitivity, faster testing speed, simple device structure and long service life of the probe.

The steps of the method for measuring the nanoscale magnetization dynamics are as follows:

1. Rotate the lens stage so that the atomic force microscope II is directly above the sample, and use the probe II to scan the area containing the sample on the waveguide to obtain the surface topography image, and preliminarily determine the position of the sample. When the probe II is located at the edge of the sample, let The probe II is retracted, and the position parameters of the atomic force microscope II are recorded;

2. Rotating the lens stage makes atomic force microscope 1 be positioned directly above the sample, and input each position parameter recorded in step 1 into atomic force microscope 1;

3. Approach probe I to the surface of the sample, and then use probe I to scan the area where the sample is located at a scanning speed of 2 nm/s. Once the surface of the sample is detected, the approach is stopped, and the distance is retracted upwards by 100 nm, and the atomic force microscope is turned off at the same time. I scan feedback;

4. Adjust the plane mirror position so that the laser beam is projected onto the probe 1 through the lens stage and the atomic force microscope 1;

5. The pulse laser generates pulsed laser, the period is less than 100fs, the repetition rate is 50MHz, the wavelength is 700nm, and the trigger waveform of the signal generator is synchronized with the laser repetition rate;

6. The signal generator generates an RF current with a frequency f of 1GHz and outputs it to the waveguide for exciting the sample;

7. In the state of turning off the scanning feedback of the atomic force microscope 1, set the probe 1 to scan;

8. The light beam reflected from the sample surface passes through the probe I, atomic force microscope I, lens stage, convex lens II, and beam splitter in sequence and then enters the optical bridge detector, and the phase-sensitive detector will enter the signal of the optical bridge detector. The polar Kerr signal of 1GHz frequency is separated and output in the form of current;

9. After the AC component of the current output by the phase sensitive detector is amplified by 30dB through the amplifier I, it is input to the input end I of the mixer;

10. The sinusoidal signal generator is frequency-locked to the signal generator to generate a reference signal with a frequency of f-Δf, Δf ₌ 3KHz, and the reference signal is input to the input terminal II of the mixer;

11. The frequency of the mixing signal output by the mixer is Δf, the mixing signal is continuously amplified by the amplifier II, and finally sampled by the analog-to-digital converter;

12. The computer records the signal output by the analog-to-digital converter, performs fast Fourier transform on the signal at the Δf frequency, and correlates it with the sample position data collected by the atomic force microscope 1, thereby obtaining a magnetic resonance image of the sample surface.

The beneficial effects of the present invention are:

The invention can measure a single nanostructure, and can measure the magnetization dynamics of the sample surface to reach the spatial resolution of sub-micron level, has high spatial sensitivity, simple device and fast test speed. The probe I and probe II are atomic force microscope probes with the same outer edge size, which are respectively used for contact mode AFM scanning and near-field time-resolved magneto-optical Kerr effect experiments. The advantage is that there is no need to use probe I to scan a large area. The surface of the sample will not cause damage to the nano-scale pore size in the probe I and affect the experimental accuracy.

Description of drawings

Further illustrate below in conjunction with the graphics of the present invention:

Figure 1 is a schematic diagram of the present invention.

FIG. 2 is a bottom view of the lens stage.

In the figure, 1. Pulse laser, 2. Delayer, 3.1/4 wave plate, 4. Concave lens, 5. Convex lens I, 6. Flat mirror, 7. Polarizer, 8. Beam splitter, 9. Convex lens II, 10 .Lens stage, 11. AFM I, 12. Probe I, 13. Lens holder, 14. Objective lens, 15. Sample, 16. Waveguide, 17. Sample stage, 18. Signal generator, 19. Oscilloscope, 20. Optical Bridge Detector, 21. Bias Tee, 22. Amplifier I, 23. Mixer, 24. Amplifier II, 25. Analog-to-Digital Converter, 26. Computer, 27. Atomic Force Microscope II, 28. Probe II .

Detailed ways

1 is a schematic diagram of the present invention, the pulsed laser 1, the signal generator 18, the waveguide 16, and the oscilloscope 19 are connected by cables in sequence, the optical bridge detector 20, the bias tee 21, the amplifier I22, the mixer 23, The amplifier II24, the analog-to-digital converter 25, and the computer 26 are connected with cables in sequence, and the laser beam emitted by the pulsed laser 1 passes through the delay device 2, the 1/4 wave plate 3, the concave lens 4, the convex lens I5, the plane mirror 6, and the polarizer 7 in turn. , beam splitter 8, convex lens II9, lens stage 10, atomic force microscope I11, probe I12, thereby forming an incident light path, and the reflected light generated by the laser beam irradiating the surface of the sample 15 passes through the probe I12, atomic force microscope I11, lens in turn Stage 10, convex lens II9, beam splitter 8, thereby forming a reflected light path, the reflected light is deflected by beam splitter 8 to the optical bridge detector 20, the probe II28 is a contact-type atomic force microscope probe, and the waveguide 16 On the sample stage 17, the sample 15 is prepared in direct contact with the upper surface of the waveguide 16 by the magnetron sputtering method, the probe I12 and the probe II28 are atomic force microscope probes with the same external dimensions, and the external shapes are both circular truncated, The axis of the frustum is perpendicular to the horizontal plane, and the probe I12 has a frustum-shaped through hole; the diameter of the upper bottom surface of the outer frustum of the probe I12 and the probe II28 is 3 microns, and the diameter of the lower bottom surface is 2 microns, so The diameter of the upper opening of the frustum-shaped through hole in the probe I12 is 500 nanometers, the diameter of the lower opening is 900 nanometers, the diameter of the lens stage 10 is ten centimeters; the length of the waveguide 16 is 80 micrometers, and the width is 50 micrometers , the thickness is 150 nanometers, and the characteristic impedance is 50 ohms; the sample 15 is 10 micrometers long, 9 micrometers wide, and 50 nanometers thick.

2 is a bottom view of the lens stage, the atomic force microscope II27 has the same structure as the atomic force microscope I11, the probe I12 is located at the lower end of the atomic force microscope I11, the probe II28 is located at the lower end of the atomic force microscope II27, and the objective lens 14 is located at the lens seat 13 at the lower end, the probe I12 and the probe II28 are atomic force microscope probes with the same external dimensions, the lens stage 10 is a light-transmitting disc and has a central axis, the atomic force microscope I11, the lens holder 13, the atomic force microscope II27 They are respectively located under the lens stage 10 and can be fine-tuned relative to the position of the lens stage 10. When the lens stage 10 is rotated around its central axis, the atomic force microscope I11 or the lens holder 13 or the atomic force microscope II27 can be placed directly above the sample 15. .

The measuring device mainly includes a pulsed laser 1, a delay device 2, a quarter wave plate 3, a concave lens 4, a convex lens I5, a plane mirror 6, a polarizer 7, a beam splitter 8, a convex lens II9, a lens stage 10, an atomic force microscope I11, a probe Needle I12, Lens Holder 13, Objective Lens 14, Sample 15, Waveguide 16, Sample Stage 17, Signal Generator 18, Oscilloscope 19, Optical Bridge Detector 20, Bias Tee 21, Amplifier I22, Mixer 23, Amplifier II24 , analog-to-digital converter 25, computer 26, atomic force microscope II27, probe II28, phase sensitive detector, sinusoidal signal generator, incident light path and reflected light path, the input end of the optical bridge detector 20 has a 45-degree angle Polarizer, the atomic force microscope II27 has the same structure as the atomic force microscope I11, the probe I12 is located at the lower end of the atomic force microscope I11, the probe II28 is located at the lower end of the atomic force microscope II27, the objective lens 14 is located at the lower end of the lens holder 13, the pulse The laser 1, the signal generator 18, the waveguide 16, and the oscilloscope 19 are connected by cables in sequence. The optical bridge detector 20, the bias tee 21, the amplifier I22, the mixer 23, the amplifier II24, the analog-to-digital converter 25, and the computer 26 The cables are connected in sequence, and the laser beam emitted by the pulsed laser 1 passes through the delay device 2, the 1/4 wave plate 3, the concave lens 4, the convex lens I5, the plane mirror 6, the polarizer 7, the beam splitter 8, the convex lens II9, and the lens stage. 10. Atomic force microscope I11 and probe I12, thereby forming an incident light path, and the reflected light generated by the laser beam irradiating the surface of the sample 15 passes through the probe I12, the atomic force microscope I11, the lens stage 10, the convex lens II9, and the beam splitter 8 in sequence, Thus, a reflected light path is formed, the reflected light is deflected by the beam splitter 8 to the optical bridge detector 20, the lens stage 10 is a light-transmitting disc and has a central axis, the atomic force microscope I11, the lens holder 13, the atomic force The microscope II27 is located under the lens stage 10, and can be fine-tuned relative to the position of the lens stage 10. When the lens stage 10 is rotated around its central axis, the atomic force microscope I11 or the lens holder 13 or the atomic force microscope II27 can be placed on the sample 15 respectively. Right above, the probe II28 is a contact-type atomic force microscope probe, the waveguide 16 is located on the sample stage 17, and the sample 15 is prepared directly on the upper surface of the waveguide 16 by magnetron sputtering. The needle II28 is an atomic force microscope probe with the same external dimensions, and the external shape is a circular truncated cone, the axis of the circular truncated cone is perpendicular to the horizontal plane, and the probe I12 has a circular truncated through hole; the probe I12 and the probe II28 have the The diameter of the upper bottom surface of the outer frustum is 3 micrometers, the diameter of the lower bottom surface is 2 micrometers, the diameter of the upper opening of the frustum-shaped through hole in the probe I12 is 500 nanometers, and the diameter of the lower opening is 900 nanometers, and the lens stage 10 The diameter is ten centimeters; the length of the waveguide 16 is 80 microns, the width is 50 microns, the thickness is 150 nanometers, and the characteristic impedance is 5 0 ohm; the sample 15 is 10 microns long, 9 microns wide, and 50 nanometers thick.

其中I₀是反射光到达所述偏振器时的光强，θ_k是克尔角。所述混频器23具有输入端I和输入端II的两个信号输入端。当反射光强对样品磁化的依赖关系是线性的，能够估计光桥探测器20中的由样品磁化导致的电流的交流分量δI≈I_DCθ_K0δm_z，其中θ_K0是样品在磁化饱和条件下的克尔角，δm_z是面外磁化的变化，I_DC是光桥探测器中的电流的直流分量。The output end of the optical bridge detector 20 is connected to the input end of a phase sensitive detector, the reference frequency of the phase sensitive detector is set to be consistent with the output frequency of the signal generator 18, and the output end of the phase sensitive detector is connected to the offset. Set the tee, and the output terminal of the sine signal generator is connected to the input terminal II of the mixer. The input end of the optical bridge detector 20 has a polarizer with an angle of 45 degrees. After the reflected light passes through the polarizer, the light intensity is

where I ₀ is the light intensity of the reflected light when it reaches the polarizer, and θ _k is the Kerr angle. The mixer 23 has two signal input terminals, input terminal I and input terminal II. When the dependence of the reflected light intensity on the sample magnetization is linear, it is possible to estimate the AC component of the current in the optical bridge detector 20 caused by the sample magnetization δI≈I _DC θ _K0 δm _z , where θ _K0 is the sample at the magnetization saturation condition The Kerr angle below, δm _z is the change in out-of-plane magnetization, and I _DC is the DC component of the current in the optical bridge detector.

The steps of the method for measuring the nanoscale magnetization dynamics are as follows:

1. Rotate the lens stage 10 so that the atomic force microscope II27 is located directly above the sample 15, use the probe II28 to scan the area containing the sample 15 on the waveguide 16 to obtain a surface topography image, and preliminarily determine the position of the sample. When the probe II28 is located at the sample When the edge is 15, retract the probe II28, and record the position parameters of the atomic force microscope II27;

2. Rotate the lens stage 10 so that the atomic force microscope I11 is directly above the sample 15, and input the position parameters recorded in the step 1 into the atomic force microscope I11;

3. Approach the surface of the sample 15 with the probe I12, and then use the probe I12 to scan the area where the sample 15 is located at a scanning speed of 2 nm/s. Once the surface of the sample is detected, the approach is stopped, and the distance is retracted upward by 100 nm, and the Scanning feedback of AFM I11;

4. Adjust the position of the plane mirror 6 so that the laser beam passes through the lens stage 10 and the atomic force microscope I11 and hits the probe I12:

5. The pulse laser 1 generates pulsed laser light, the period is less than 100fs, the repetition rate is 50MHz, the wavelength is 700nm, and the trigger waveform of the signal generator 18 is synchronized with the laser repetition rate;

6. The signal generator 18 generates an RF current with a frequency f of 1 GHz and outputs it to the waveguide 16 for exciting the sample;

7. In the state of turning off the scanning feedback of the atomic force microscope I11, set the probe I12 to scan;

8. The light beam reflected from the surface of the sample 15 passes through the probe I12, the atomic force microscope I11, the lens stage 10, the convex lens II9, and the beam splitter 8 in sequence, and then enters the optical bridge detector 20, and the phase-sensitive detector will enter the optical bridge detector. The polar Kerr signal of 1GHz frequency in the signal of 20 is separated and output in the form of current;

9. After the AC component of the current output by the phase sensitive detector is amplified by 30dB through the amplifier I22, it is input to the input end I of the mixer 23;

10. The sinusoidal signal generator is frequency-locked to the signal generator 18 to generate a reference signal with a frequency of f-Δf, Δf ₌ 3KHz, and the reference signal is input to the input terminal II of the mixer 23;

11. The frequency of the mixed signal output by the mixer 23 is Δf, and the mixed signal is continuously amplified by the amplifier II24, and finally sampled by the analog-to-digital converter 25;

12. The computer 26 records the signal output by the analog-to-digital converter 25, performs fast Fourier transform on the signal at the Δf frequency, and correlates it with the sample position data collected by the atomic force microscope I11, thereby obtaining the magnetic resonance of the sample surface image.

The measurement device uses a high-precision positioning device to obtain the magnetization information of the nanoscale sample surface, that is, two different atomic force microscope tips are used to conduct contact mode atomic force microscope scanning and near-field time-resolved magneto-optical Kerr effect experiments, and use frequency domain. The method to detect the magnetization dynamics of the sample surface in the GHz frequency band has the advantages of higher spatial sensitivity, faster testing speed, simple device structure and long service life of the probe. The invention can measure a single nanostructure, and can measure the magnetization dynamics of the sample surface to reach the spatial resolution of sub-micron level, has high spatial sensitivity, simple device and fast test speed.

Claims (1)

1. A method for measuring nanoscale magnetization dynamics, the measuring device mainly includes a pulsed laser, a delay device, a 1/4 wave plate, a concave lens, a convex lens I, a plane mirror, a polarizer, a beam splitter, a convex lens II, a lens stage, an atomic force Microscope I, Probe I, Lens Holder, Objective Lens, Sample, Waveguide, Sample Stage, Signal Generator, Oscilloscope, Optical Bridge Detector, Bias Tee, Amplifier I, Mixer, Amplifier II, A/D Converter, Computer, atomic force microscope II, probe II, phase sensitive detector, sinusoidal signal generator, incident light path and reflected light path, the input end of the optical bridge detector has a polarizer with an angle of 45 degrees, and the mixer has Input end I and input end II, the atomic force microscope II has the same structure as the atomic force microscope I, the probe I is located at the lower end of the atomic force microscope I, the probe II is located at the lower end of the atomic force microscope II, the objective lens is located at the lower end of the lens seat, The pulsed laser, the signal generator, the waveguide, and the oscilloscope are connected by cables in sequence, and the optical bridge detector, bias tee, amplifier I, mixer, amplifier II, analog-to-digital converter, and computer are connected by cables in sequence. The laser beam emitted by the pulsed laser passes through the delayer, 1/4 wave plate, concave lens, convex lens I, plane mirror, polarizer, beam splitter, convex lens II, lens stage, atomic force microscope I, and probe I in turn to form an incident optical path. , the reflected light generated by the laser beam irradiating the sample surface passes through the probe I, the atomic force microscope I, the lens stage, the convex lens II, and the beam splitter in sequence to form a reflected light path, and the reflected light is deflected by the beam splitter to the Optical bridge detector, the lens stage is a light-transmitting disc and has a central axis, the AFM I, the lens holder, and the AFM II are respectively located under the lens stage, and can be fine-tuned relative to the position of the lens stage, when the lens When the stage rotates around its central axis, the AFM I or the lens holder or the AFM II can be placed directly above the sample, respectively. The probe II is a contact-type AFM probe, and the waveguide is located on the sample stage. The sample is prepared in direct contact with the upper surface of the waveguide, the probe I and the probe II are atomic force microscope probes with the same external dimensions, and the shapes are both circular truncated cones, the axis of the circular truncated cone is perpendicular to the horizontal plane, and the probes There is a frustum-shaped through hole in the probe I and the outer frustum of the probe I and the probe II. The diameter of the upper bottom surface is 3 microns, and the diameter of the lower bottom surface is 2 microns. The frustum shaped through hole in the probe I The diameter of the upper opening is 500 nanometers, the diameter of the lower opening is 900 nanometers, the diameter of the lens stage is ten centimeters, the length of the waveguide is 80 micrometers, the width is 50 micrometers, the thickness is 150 nanometers, and the characteristic impedance is 50 ohms. The length of the sample is 10 microns, the width is 9 microns, and the thickness is 50 nanometers. The output end of the optical bridge detector is connected to the input end of the phase-sensitive detector, and the reference frequency of the phase-sensitive detector is set to be the same as that of the signal generator. The output frequency of the phase sensitive detector is the same, the output end of the phase sensitive detector is connected to the bias tee, the output end of the sine signal generator is connected to the input end II of the mixer, and the reflected light passes through the bias tee. The light intensity after the vibrator is

where I ₀ is the light intensity of the reflected light when it reaches the polarizer, and θ _k is the Kerr angle. When the dependence of the reflected light intensity on the sample magnetization is linear, it is possible to estimate the optical bridge detector caused by the sample magnetization. The AC component of the current δI≈I _DC θ _K0 δm _z , where θ _K0 is the Kerr angle of the sample at magnetization saturation, δm _z is the change in out-of-plane magnetization, and I _DC is the DC component of the current in the optical bridge detector , It is characterized in that, the steps of the method for measuring the nanoscale magnetization dynamics are as follows: 1. Rotate the lens stage so that the atomic force microscope II is directly above the sample, and use the probe II to scan the area containing the sample on the waveguide to obtain the surface topography image, and preliminarily determine the position of the sample. When the probe II is located at the edge of the sample, let The probe II is retracted, and the position parameters of the atomic force microscope II are recorded; 2. Rotating the lens stage makes atomic force microscope 1 be positioned directly above the sample, and input each position parameter recorded in step 1 into atomic force microscope 1; 3. Approach probe I to the surface of the sample, and then use probe I to scan the area where the sample is located at a scanning speed of 2 nm/s. Once the surface of the sample is detected, the approach is stopped, and the distance is retracted upwards by 100 nm, and the atomic force microscope is turned off at the same time. I scan feedback; 4. Adjust the plane mirror position so that the laser beam is projected onto the probe 1 through the lens stage and the atomic force microscope 1; 5. The pulse laser generates pulsed laser, the period is less than 100fs, the repetition rate is 50MHz, the wavelength is 700nm, and the trigger waveform of the signal generator is synchronized with the laser repetition rate; 6. The signal generator generates an RF current with a frequency f of 1GHz and outputs it to the waveguide for exciting the sample; 7. In the state of turning off the scanning feedback of the atomic force microscope 1, set the probe 1 to scan; 8. The light beam reflected from the sample surface passes through the probe I, atomic force microscope I, lens stage, convex lens II, and beam splitter in sequence and then enters the optical bridge detector, and the phase-sensitive detector will enter the signal of the optical bridge detector. The polar Kerr signal of 1GHz frequency is separated and output in the form of current; 9. After the AC component of the current output by the phase sensitive detector is amplified by 30dB through the amplifier I, it is input to the input end I of the mixer; 10. The sinusoidal signal generator is frequency-locked to the signal generator to generate a reference signal with a frequency of f-Δf, Δf ₌ 3KHz, and the reference signal is input to the input terminal II of the mixer; 11. The frequency of the mixing signal output by the mixer is Δf, the mixing signal is continuously amplified by the amplifier II, and finally sampled by the analog-to-digital converter; 12. The computer records the signal output by the analog-to-digital converter, performs fast Fourier transform on the signal at the Δf frequency, and correlates it with the sample position data collected by the atomic force microscope 1, thereby obtaining a magnetic resonance image of the sample surface.

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