System and Method for Comprehensive Testing and Analysis of Micro-area Magneto-optic Parameters, Optical Constants and Magnetic Domains

Abstract

This invention discloses a comprehensive testing and analysis system and method for micro-area magneto-optical parameters, optical constants, and magnetic domains, belonging to the field of magnetic material testing and analysis technology. The system includes: a light source module for emitting a parallel beam; a beam homogenization and shaping module for compensating the incident parallel beam and outputting a uniform parallel beam; a polarization modulation module for deflecting the uniform parallel beam to generate linearly polarized light and modulating the polarization state of the linearly polarized light to generate approximately linearly polarized light with a high polarization state and performing polarization detection; an electromagnet sample stage for placing the sample to be tested and controlling the magnetic field environment of the sample; an imaging detection module for acquiring the light intensity signal after being acted upon by the sample and converting it into image data; and a control and analysis module for controlling the operation of each module, calculating the optical constants and magneto-optical parameters of the sample to be tested, and dynamically observing changes in magnetic domains based on the acquired light intensity signal and image data.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of magnetic material testing and analysis, and particularly relates to a micro-area magneto-optical parameter, optical constant and magnetic domain comprehensive testing and analysis system and method. BACKGROUND

[0002] In the design and application field of magnetic materials, the accurate determination of magneto-optical parameters and optical constants is crucial, and the parameters have a decisive influence on the characterization of material performance, function implementation and technical application. However, in the micro-area testing field of magnetic materials, the traditional testing method has certain limitations: the testing of magneto-optical parameters mainly relies on the magneto-optical Kerr system, and the testing of optical constants is mainly realized by an ellipsometer, and the two testing means are respectively for different physical properties, so in actual operation, if the two types of parameters are to be measured, two tests need to be performed by changing the testing equipment, which is complex and costly. Therefore, the present application proposes a spectral magneto-optical ellipsometry device using a rotating compensator, which can obtain the magneto-optical parameters and optical constants of the magnetic thin film material through one test.

[0003] Magnetic domain refers to a small magnetization area with different directions produced by the differentiation of magnetic materials in the process of spontaneous magnetization to reduce static magnetic energy, and the size and structure of the magnetic domain directly affect the magnetization behavior or characteristics of the magnetic material. For example, the size of the magnetic domain can affect the coercivity and magnetization process of the material, and therefore, accurate analysis of the magnetic domain size and the moving speed of the magnetic domain wall is very important for the design and application of magnetic materials. For this characteristic of magnetic domain, a specific device with straight incidence is currently used for observation. Due to the differences in devices, structures and principles, the existing magnetic domain observation device cannot be directly integrated with other devices such as the above-mentioned spectral magneto-optical ellipsometry device, and it is impossible to realize the comprehensive testing of optical constants and magnetic parameters while observing the dynamic magnetic domain. If synchronous observation of these magnetic material characteristics is required, two or even multiple tests need to be performed, which is complex and costly, and the multiple testing operations can easily cause the test micro-area to deviate, thereby making it difficult to provide effective data support for the correlation analysis between different property parameters of the magnetic material. SUMMARY

[0004] In view of the deficiencies of the prior art, the present application provides a micro-area magneto-optical parameter, optical constant and magnetic domain comprehensive testing and analysis system and method, which can realize the synchronous comprehensive testing and analysis of magneto-optical parameters and ellipsometric parameters and the dynamic observation of magnetic domains in the same micro-area through one test of the magneto-optical parameters, optical constants and dynamic observation of magnetic domains of the magnetic material in the same micro-area, thereby establishing a bridge between the optical properties and magnetic properties of the material, and avoiding the drawbacks of complex operation and high cost caused by the need for multiple devices and multiple measurements to obtain multiple material property parameters.

[0005] To achieve the above object, one or more embodiments of the present application provide the following technical solutions:

[0006] The first aspect of the present application provides a micro-area magneto-optical parameter, optical constant and magnetic domain comprehensive test and analysis system.

[0007] A micro-area magneto-optical parameter, optical constant and magnetic domain comprehensive test and analysis system comprises:

[0008] A light source module is configured to emit parallel light beams.

[0009] A homogenization and shaping module is configured to compensate for the incident parallel light beams and output uniform parallel light beams.

[0010] A polarization modulation module is configured to deflect the uniform parallel light beams to generate linearly polarized light, modulate the polarization state of the linearly polarized light, generate approximately linearly polarized light with a high polarization state, and detect the polarization.

[0011] An electromagnet sample stage is configured to place a sample to be tested and regulate the magnetic field environment in which the sample to be tested is located.

[0012] An imaging and detection module is configured to collect light intensity signals after the sample to be tested and convert the light intensity signals into image data.

[0013] A control and analysis module is configured to control the operation of each module, calculate the optical constant, magneto-optical parameter and dynamic observation of magnetic domain changes of the sample to be tested according to the collected light intensity signals and image data.

[0014] Further technical solutions, the light source module comprises a light source, a monochromator, a fiber adapter, an incident optical fiber and a first collimating lens arranged in sequence.

[0015] The light outlet of the light source is aligned with the light inlet of the monochromator, the divergent light beam output by the light source is incident into the monochromator, and the monochromator generates a monochromatic light beam with a set wavelength.

[0016] The fiber adapter is installed at the light outlet of the monochromator, the fiber adapter is connected to the light receiving end of the incident optical fiber, and a lens pair is installed in the fiber adapter. The divergent monochromatic light beam generated by the monochromator is converged to the light receiving end of the incident optical fiber through the lens pair.

[0017] The light output end of the incident optical fiber is connected to the collimating lens, the divergent light output by the incident optical fiber is collimated through the first collimating lens, and the collimated parallel light beam is incident into the homogenization and shaping module.

[0018] Further technical solutions, the angle and position between the light outlet of the light source and the light inlet of the monochromator are adjusted to be:

[0019] At the end of the entire system polarization detection end, a light power meter and a spectrum analyzer are arranged.

[0020] The power of the received light intensity signal is measured using an optical power meter. The distance between the light outlet of the light source and the light inlet of the monochromator is continuously adjusted to maximize the power of the light intensity signal measured by the optical power meter.

[0021] By analyzing the received light intensity signal using a spectrometer, the angle between the light source's output port and the monochromator's input port is continuously adjusted to ensure that the light intensity signal analyzed by the spectrometer has optimal monochromaticity.

[0022] In a further technical solution, the light-shaping module includes a first integrating lens, a second integrating lens, and a condensing lens arranged sequentially; wherein the second integrating lens is located at the rear focal plane of the first integrating lens;

[0023] The incident parallel beam is divided into multiple secondary sources by the first integrating lens array. The secondary sources are then superimposed by the second integrating lens array and the condenser lens to compensate for the inhomogeneity of the secondary sources located in symmetrical positions, and a uniform beam is output.

[0024] A further technical solution involves a polarization modulation module comprising a second collimating lens, a polarizer, a compensator, and an analyzer arranged sequentially; wherein the polarizer and analyzer are Glan prisms, each mounted on a miniature rotating motor; the compensator is a 1 / 4" prism. A waveplate, installed in a push-pull device and connected to a motor;

[0025] The incident uniform beam is first collimated by a second collimating lens, then deflected by a polarizer to become linearly polarized light. The linearly polarized light then passes through a 1 / 4 section acting as a compensator. The waveplate modulates the polarization state, generating two polarization components with perpendicular vibration directions. The phase delay of 2 / 2 is combined and emitted as elliptically polarized light, which is then incident on the analyzer for polarization analysis.

[0026] In a further technical solution, an electromagnet sample stage is provided between the compensator and the analyzer. The electromagnet sample stage includes a monopole electromagnet and a sample stage. The sample stage is used to place the sample to be tested, and the monopole electromagnet is used to adjust the magnitude of the magnetic field of the sample to be tested.

[0027] The imaging detection module includes a microscopic imaging unit and a CMOS camera, which are respectively positioned before and after the analyzer. The microscopic imaging unit is used to amplify the light intensity signal. This unit includes a microscope objective and an imaging lens. The microscope objective has a long working distance and achromaticity, and the imaging lens has achromaticity. The CMOS camera is used to detect the light intensity signal and convert it into image data.

[0028] The second aspect of this invention provides a method for comprehensive testing and analysis of micro-area magneto-optical parameters, optical constants, and magnetic domains.

[0029] A comprehensive testing and analysis method for micro-area magneto-optical parameters, optical constants, and magnetic domains is proposed. Based on the comprehensive testing and analysis system for micro-area magneto-optical parameters, optical constants, and magnetic domains proposed in the first aspect, it enables dynamic observation of changes in optical constants, magneto-optical parameters, and magnetic domains in the same micro-area during subsequent tests. The testing process for optical constants is as follows:

[0030] Adjust the polarizer angle to 0° and the analyzer angle to 0°;

[0031] The drive push-pull device pushes the compensator in, controls the compensator to rotate at a set speed along the optical axis, and controls the monochromator to change the wavelength of the incident beam according to the set step size.

[0032] Each pixel of the CMOS camera is considered as a micro-region. The light intensity signal of each micro-region is detected, and the ellipticity parameters of the sample under test are obtained by Fourier analysis. Then, the ellipticity parameters are inverted and fitted to obtain the optical constants of the sample under test.

[0033] A further technical solution involves the following testing process for magneto-optical parameters:

[0034] The drive push-pull device pushes out the compensator, controls the polarizer angle to be adjusted to 90°, observes the CMOS camera image and rotates the polarizer to adjust the light intensity signal to the minimum, and records the initial polarizer angle X.

[0035] Adjust the magnitude of the electromagnet's magnetic field to saturate the positive magnetic field of the sample under test;

[0036] Centered on the initial polarizer angle X, the polarizer is rotated gradually within a set range according to a set step progress. At each angle, the analyzer is controlled to rotate accordingly according to the set step progress, and the angles of the polarizer and analyzer are recorded. and And record the light intensity value I+ of CMOS additive detection at each deflection angle;

[0037] Adjust the magnitude of the electromagnet's magnetic field to saturate the reverse magnetic field of the sample under test, repeat the deflection steps of the polarizer and analyzer, and record the light intensity value I- detected by CMOS at each deflection angle.

[0038] Based on the Jones matrix detected by the polarizer, analyzer, and CMOS camera, the relationship between light intensity and deflection angle is analyzed. Based on the light intensity values ​​at multiple deflection angles obtained by measurement, the reflection coefficient and magneto-optical reflection coefficient are obtained by inversion fitting, and the magneto-optical coupling coefficient is calculated.

[0039] A further technical solution involves the following process for observing magnetic domains:

[0040] Adjust the analyzer angle to 0°, observe the CMOS camera image and rotate the polarizer to minimize the light intensity signal, and record the initial polarizer angle Y.

[0041] Based on the set deviation angle, adjust the initial polarizer angle Y, adjust the electromagnet to adjust the magnetic field strength to the initial magnetization magnetic field strength, and observe the complete process of the sample being magnetized in the CMOS camera.

[0042] Further technical solutions involve preparatory work before simultaneously testing optical constants and magneto-optical parameters and dynamically observing changes in magnetic domains, including:

[0043] Preheating the electromagnet;

[0044] Turn on the power to the light source, monochromator, control and analysis module, and CMOS camera;

[0045] Adjust the incident angle of the support, which is the angle between the incident ray and the normal of the sample to be tested;

[0046] Place the sample to be tested on the electromagnet sample stage, adjust the position of the sample so that the upper surface of the sample is located at the center of the electromagnet poles, and the reflected light enters from the center of the support and is coaxial with the polarization analyzer module.

[0047] The microscopic imaging unit is moved back and forth along the optical axis, and the working distance is adjusted so that the CMOS camera can detect a clear image. At the same time, the power of the light source is adjusted to avoid saturation of the CMOS camera.

[0048] The above one or more technical solutions have the following beneficial effects:

[0049] (1) In order to solve the problem that the testing of magneto-optical parameters and optical constants and the observation of magnetic domains in the existing schemes require different equipment, the testing process is complicated and costly, and the test micro-area is easily shifted during the equipment replacement process, thus making it impossible to guarantee the accurate spatial correlation between parameters, this invention proposes a comprehensive testing and analysis system and method for micro-area magneto-optical parameters, optical constants and magnetic domains. Through integrated optical path design, the optical constant test, magneto-optical parameter test and magnetic domain dynamic observation can be completed simultaneously in the same micro-area without moving the sample or sample stage. This not only saves the cumbersome process of equipment replacement and sample repositioning, greatly shortens the testing time, but also ensures that all parameters originate from the same test area, providing accurate spatial matching data for establishing the intrinsic correlation between the optical and magnetic properties of materials, and can significantly improve the scientificity and reliability of the test results.

[0050] (2) The present invention optimizes the polarization modulation module and the imaging detection module. By designing a push-pull compensator, only one action of pushing out / pushing in the compensator is needed to switch between optical constant testing and magneto-optical parameter and magnetic domain observation testing, while keeping the positions of other optical components such as polarizer, microscope objective and electromagnet sample stage fixed, ensuring that the test conditions of the same micro-area remain unchanged, avoiding micro-area shift that affects subsequent data analysis, improving the correlation of test data, and completing three tests in a single sample loading, greatly improving test efficiency. Compared with the traditional magnetic domain observation using the direct incidence method which cannot simultaneously detect other property parameters, the present invention uses the oblique incidence optical path. When the oblique incidence light is reflected on the surface of the magnetic material, the difference in magnetic moment at the magnetic domain boundary will lead to enhanced light intensity contrast. Combined with the fine adjustment of the extinction position, the difference in light intensity signal in the magnetic domain area is further amplified. Combined with a high-resolution CMOS camera, the details of light intensity distribution within the micro-area are captured, realizing dynamic magnetic domain observation, and simultaneously realizing the detection of magneto-optical parameters and optical constants in the same micro-area, laying the foundation for realizing comprehensive testing and analysis of micro-area magneto-optical parameters, optical constants and magnetic domains.

[0051] (3) Considering that the non-uniformity of the light source will directly affect the detection accuracy of weak magneto-optical response, traditional test systems often cause parameter measurement deviations due to non-uniform light spots. Therefore, this invention introduces an integrating lens array homogenizing module composed of a first integrating lens, a second integrating lens and a condensing lens. By decomposing the incident light into multiple secondary wave sources and superimposing compensation, the flat-top factor of the light source is effectively improved. After homogenization, the test errors of ellipticity parameter and Kerr deflection angle are significantly reduced, especially the detection stability of weak signals is significantly improved, providing a reliable light source guarantee for high-precision parameter testing.

[0052] (4) This invention treats each pixel of the CMOS camera as an independent micro-region, thereby achieving accurate measurement of the optical constants and magneto-optical parameters of any micro-region on the sample surface. At the same time, the high-resolution imaging capability ensures that the details of the magnetic domains are clearly visible, enabling the device to be applied to the performance characterization of micro-devices such as nanoscale magnetic thin films and magnetic heterojunctions, effectively expanding the application range of testing technology. A dedicated monopole electromagnet is set up to support the free adjustment of the incident angle, so that the magnetic field strength is stable and continuously adjustable within the effective range, and the magnetic pole can move flexibly in the x-axis and z-axis directions, which can adapt to the testing requirements of different magnetic materials (such as perpendicular magnetic anisotropic thin films, multilayer magnetic thin films, etc.). The design of the push-pull compensator realizes the rapid switching of testing functions. Combined with the software-controlled polarization device angle adjustment, the system can flexibly select test parameters according to the sample characteristics, improving the compatibility with diverse samples. Attached Figure Description

[0053] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0054] Figure 1 This is a schematic diagram of the structure of the comprehensive testing and analysis system for micro-area magneto-optical parameters, optical constants, and magnetic domains in an embodiment of the present invention;

[0055] Figure 2 This is a schematic diagram of the electromagnet sample stage in an embodiment of the present invention;

[0056] Figure 3 This is a schematic diagram of the light intensity distribution of the light source before and after homogenization in an embodiment of the present invention; wherein, (a) is the light intensity distribution of the incident ideal Gaussian beam and the uniform beam after homogenization, and (b) is a schematic diagram of the flat-top factor of the light source before and after homogenization.

[0057] Figure 4 This is a schematic diagram showing the distribution of the absolute value of measurement error before and after homogenization in an embodiment of the present invention; where (a), (b), and (c) are the absolute values ​​of error obtained by subtracting the Gaussian light source measurement results from the noise-free ideal results. , as well as Spatial distribution; (d), (e), and (f) are the absolute values ​​of the test error of the light source after homogenization and shaping. , as well as Spatial distribution;

[0058] Figure 5 This is a schematic diagram of the continuous change pattern of magnetic domains in a Co-based magnetic heterojunction in an embodiment of the present invention; wherein (a) to (h) are images continuously acquired under the condition of continuous change of magnetic field.

[0059] The components include: 1. Light source; 2. Monochromator; 3. First collimating lens; 4. Beam homogenizing and shaping module; 4-1. First integrating lens; 4-2. Second integrating lens; 4-3. Condensing lens; 5. Second collimating lens; 6. Polarizer; 7. Compensator; 8. Electromagnetic sample stage; 9. Microscope objective; 10. Imaging lens; 11. Analyzer; and 12. CMOS camera. Detailed Implementation

[0060] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0061] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0062] Example 1

[0063] To address the limitations of existing methods in repeatedly measuring optical constants, magneto-optical parameters, and dynamically observing magnetic domains within the same micro-region, as well as the issue of light source uniformity, this embodiment proposes a comprehensive testing and analysis system for micro-region magneto-optical parameters, optical constants, and magnetic domains. Figure 1 As shown, it specifically includes:

[0064] The light source module is used to emit a parallel beam of light;

[0065] The beam shaping module is used to compensate for the incident parallel beam and output a uniform parallel beam.

[0066] The polarization modulation module is used to deflect a uniform parallel beam to generate linearly polarized light, and modulate the polarization state of the linearly polarized light to generate approximately linearly polarized light with a high polarization state and perform polarization detection to meet the testing requirements of different parameters.

[0067] An electromagnet sample stage is used to place the sample to be tested and to control the magnetic field environment of the sample to meet the requirements of different magnetic materials for magnetic field and incident angle under different test conditions.

[0068] The imaging detection module is used to collect the light intensity signal after it has been acted upon by the sample and convert it into image data.

[0069] The control and analysis module is used to control the operation of each module, calculate the optical constants, magneto-optical parameters, and dynamically observe the changes in magnetic domains of the sample under test based on the collected light intensity signals and image data.

[0070] The following content provides a more detailed introduction to the comprehensive testing and analysis system for micro-area magneto-optical parameters, optical constants, and magnetic domains proposed in this embodiment.

[0071] (1) Light source module

[0072] The light source module is responsible for providing the entire system with incident light that is monochromatic, stable, and powerful. This module includes a light source 1, a monochromator 2, an optical fiber adapter, an incident optical fiber, and a first collimating lens 3, arranged sequentially. Specifically, the output port of the light source 1 is aligned with the input port of the monochromator 2. The divergent beam output by the light source enters the monochromator 2, which generates a monochromatic beam of a set wavelength. An optical fiber adapter is installed at the output port of the monochromator 2. The optical fiber adapter is connected to the optical receiving end of the incident optical fiber. A lens pair is installed in the optical fiber adapter, which focuses the divergent monochromatic beam generated by the monochromator to the optical receiving end of the incident optical fiber. The optical output end of the incident optical fiber is connected to the collimating lens 3. The first collimating lens 3 collimates the divergent light output from the incident optical fiber, and the collimated parallel beam enters the uniform beam shaping module.

[0073] In this embodiment, the CEL-S500 xenon lamp light source from Zhongjiao Jinyuan is selected as the output light source. The output divergent beam is incident on a monochromator, which is used in conjunction with the light source to generate the desired monochromatic light. During the test, the output wavelength of the light source is selected through the monochromator, thereby achieving spectral measurement. When selecting a monochromator, monochromaticity, positioning accuracy, and wavelength repeatability must be considered simultaneously. In this embodiment, the SBP300 monochromator from Zhuoli Hanguang is selected. The light outlet of the xenon lamp light source is aligned with the light inlet of the monochromator. The desired output wavelength is selected through the monochromator control software, thereby outputting a monochromatic beam of the set wavelength, such as monochromatic light in the range of 400~700 nm. A fiber optic adapter is installed at the output port of the monochromator to export monochromatic light. In this embodiment, the BFC-441 fiber optic adapter from Zolix Optoelectronics is selected. This adapter is compatible with the SBP300 monochromator and is suitable for Φ10 mm cylindrical interface type optical fibers or fiber bundles. Furthermore, a lens pair is installed in the fiber optic adapter. The lens pair can focus the diverging light emitted by the monochromator onto the light receiving end of the incident fiber, thereby obtaining higher light intensity efficiency. The incident fiber is the FLG-407 fiber from Zolix Optoelectronics' FLG series, with a working wavelength range of 200~1100nm. The A-end interface is a Φ10 mm cylindrical interface connected to the fiber optic adapter, and the B-end interface is an SMA905, which is connected to the first collimating lens.

[0074] As one implementation method, considering that the light emitted from the optical fiber is divergent, while parallel light is required in the measurement process of this system, a collimating lens is needed to collimate the divergent light. In this embodiment, a first collimating lens is provided. The monochromatic beam converged by the fiber optic adapter is collimated by the first collimating lens before being incident on the homogenizing and shaping module. To prevent the coupling efficiency from decreasing due to chromatic aberration at different wavelengths, the selected collimating lens also needs to have achromatic characteristics in the 400~700nm band. Therefore, an Edmund achromatic lens is used in this system, and it is coated with an antireflection coating for the visible to near-infrared band.

[0075] Preferably, to ensure that the light emitted by the light source module has the best monochromaticity and maximum light intensity, the angle and position between the xenon lamp light source's output port and the monochromator's input port need to be adjusted. The adjustment process is as follows: At the very end of the entire system's polarization end (i.e., after the polarizer and in front of the CMOS camera), place an optical power meter and a spectrum analyzer. Use the optical power meter to measure the power of the received light intensity signal, and continuously adjust the distance between the xenon lamp light source's output port and the monochromator's input port to maximize the power of the light intensity signal measured by the optical power meter. Use Ocean Optics' STS-VIS spectrum analyzer to analyze the received light intensity signal, and continuously adjust the angle between the light source's output port and the monochromator's input port to ensure that the light intensity signal analyzed by the spectrum analyzer has optimal monochromaticity. At this point, determine the angle between the xenon lamp light source's output port and the monochromator's input port.

[0076] (2) Uniform light shaping module

[0077] Considering that the non-uniformity of the light source itself, the slight positional error of optical devices, the unavoidable dust on the lens, and the speckle in laser illumination can all lead to non-uniformity of the final illumination light, which will directly affect the accuracy of detection, especially for the detection of weak magneto-optical responses, this embodiment also adds a uniform light shaping module 4. After comprehensively considering the uniform light effect and the wavelength of the illumination light, an integrating lens array is selected as the uniform light shaping module in the imaging magneto-optical ellipsometric. The uniform light shaping module includes three components, namely a first integrating lens 4-1, a second integrating lens 4-2, and a condenser lens 4-3 arranged in sequence. The second microlens array is located near the back focal plane of the first microlens array. Specifically, the incident parallel beam is divided into multiple secondary sources by the first integrating lens array, and the uniformity of each secondary source is optimized. Then, the decomposed secondary sources are superimposed by the second integrating lens array and the condenser lens, and the non-uniformity of the secondary sources located in symmetrical positions is further compensated, and finally a uniform beam is output. Preferably, in this embodiment, the integrating lens is selected from Soleber's MLA1, and the condensing lens is selected from Soleber's AC254 030-A-ML.

[0078] (3) Polarization modulation module

[0079] The polarization modulation module includes a second collimating lens 5, a polarizer 6, a compensator 7, and an analyzer 11 arranged sequentially; wherein the polarizer and analyzer are Glan prisms, respectively mounted on a miniature rotary motor; the compensator is a 1 / 4" prism. A waveplate is installed in a push-pull system and connected to a motor. Specifically, the incident uniform beam is first collimated by a second collimating lens, then deflected by a polarizer to produce linearly polarized light. The linearly polarized light then passes through a 1 / 4 section acting as a compensator. The waveplate modulates the polarization state, generating two polarization components with perpendicular vibration directions. The phase delay of 2 / 2 is combined and emitted as elliptically polarized light, which is then incident on the analyzer for polarization analysis.

[0080] To generate approximately linearly polarized light with a high polarization state, a polarizer with a high extinction ratio is required. Therefore, this embodiment uses Union Optic's Glan prism PGT5008 as both the polarizer and analyzer. This Glan prism is made of Iceland spar and operates in the 350–2300 nm wavelength range, including the required testing wavelength range of 400–700 nm. Furthermore, to more accurately determine the angles of the polarizer and analyzer, they are mounted on a miniature rotary motor, allowing for precise control of their rotation via computer software.

[0081] To measure magneto-optical parameters and optical constants within the same micro-region, it is necessary to modulate the polarization state of the polarized light. Therefore, in this embodiment, 1 / 4 A waveplate, used as a compensator, employs specific materials and thicknesses to generate two polarization components with perpendicular vibration directions after linearly polarized light passes through it. A phase delay of 1 / 2 results in elliptically polarized light synthesized under this phase difference, and 1 / 4 Waveplates can be used to isolate reflected light. Furthermore, a push-in, quick-release compensator is connected to a motor to achieve rotation at a specific speed, thereby modulating the polarization state of the polarized light.

[0082] (4) Electromagnet sample stage

[0083] An electromagnet sample stage 8 is positioned between the polarizer and the analyzer, and includes a monopole electromagnet and a sample stage; the sample stage is used to place the sample to be tested, and the monopole electromagnet is used to adjust the magnitude of the magnetic field around the sample to be tested.

[0084] Specifically, based on the testing principle of poloidal magneto-optical ellipsometrics, the electromagnet is required to provide an out-of-plane magnetic field sufficient to saturate the sample, and the pole size must be suitable for fixing the sample. When the incident angle is large or small, the electromagnet coil should not affect the optical path. To meet the testing requirements of poloidal magneto-optical ellipsometrics and achieve a larger adjustable range of incident angles and a more average and stable out-of-plane magnetic field, this embodiment designs a dedicated monopole electromagnet, such as... Figure 2As shown, a corresponding regulated power supply and water cooling system are also configured to achieve a stable and continuously adjustable magnetic field within the range of 0-3200 Oe. Furthermore, the magnetic pole center is integrated with the sample stage, and the monopole structure ensures that the light incident angle can be arbitrarily selected within the range of 0° to 90°. The magnetic pole diameter is 50 mm, and the magnetic head end face diameter is 20 mm. To facilitate adjustment of the optical path and sample position, the magnetic field strength of the electromagnet is controlled by software. The electromagnet's magnetic poles can be continuously adjusted within a range of 20 mm in the z-axis direction and within a range of 50 mm in the x-axis direction. With the magnetic poles extending 20 mm, the maximum central magnetic field can reach 2500 Oe, which can meet the requirements for poloidal magneto-optical ellipsometric testing of most perpendicular magnetic anisotropic samples.

[0085] (5) Imaging detection module

[0086] The imaging detection module includes a microscopic imaging unit and a CMOS camera 12, which are respectively positioned before and after the analyzer. The microscopic imaging unit is used to amplify the light intensity signal. This unit includes a microscope objective 9 and an imaging lens 10. The microscope objective has a long working distance and achromaticity, and the imaging lens has achromaticity. The CMOS camera is used to detect the light intensity signal and convert it into image data.

[0087] Furthermore, the microscope objective and the imaging lens together constitute the microscope imaging unit of the system, which determines the system's resolution and magnification. Since the system uses oblique incidence, to avoid structural interference between the sample stage and the microscope objective, this embodiment employs a microscope objective with a long working distance. Similarly, to avoid a decrease in coupling efficiency due to chromatic aberration, both the microscope objective and the imaging lens need to be achromatic. For example, the microscope objective is a Mitutoyo 378-803-3 model with a long working distance, and the imaging lens is a Thorlabs AC254-100-A-ML model achromatic cemented doublet lens.

[0088] In addition, considering that the system needs to measure the entire sample area during the measurement process and the micro-area is small, the camera needs to have high resolution and a large field of view. CMOS industrial cameras have the advantages of high performance and high-quality imaging, and can meet the requirements for extracting light intensity in ellipsometric measurements. Therefore, this embodiment selects a CMOS camera as the data acquisition device. For example, the GS3-U3-23S6C-C camera from Teledyne FLIR's Grasshopper3 USB3 series can be used. This camera is small in size, lightweight, and highly flexible, and can be directly integrated into the system.

[0089] Example 2

[0090] This embodiment proposes a comprehensive testing and analysis method for micro-area magneto-optical parameters, optical constants, and magnetic domains. Based on the comprehensive testing and analysis system for micro-area magneto-optical parameters, optical constants, and magnetic domains proposed in the first aspect, it enables dynamic observation of changes in optical constants, magneto-optical parameters, and magnetic domains in the same micro-area during subsequent tests. Furthermore, it does not require moving the sample or sample stage when performing multiple testing functions, thus ensuring the accuracy of testing the same micro-area.

[0091] Specifically, the following preparations should be made before the test:

[0092] 1) Turn on the electromagnet control system to preheat the electromagnet.

[0093] 2) Turn on the power to the xenon lamp light source, monochromator, CMOS camera, and control and analysis module (including motor control module and computer).

[0094] 3) Rotate the supports of the polarization arm and the polarization detection arm of the support to select the incident angle φ. Here, the incident angle φ is the angle between the incident ray and the sample normal.

[0095] 4) Place the sample to be tested (i.e. the thin film sample to be tested) on the electromagnet sample stage and adjust the sample position so that the upper surface of the sample is located at the center of the electromagnet pole. At this time, the reflected light enters from the center of the support and is on the same optical axis as the polarization analyzer module.

[0096] 5) Move the microscopic imaging unit back and forth along the optical axis to adjust the working distance so that the CMOS camera can obtain a clear image. At the same time, adjust the power of the xenon lamp source to avoid saturation of the CMOS camera.

[0097] The testing process for each function will be explained in detail below.

[0098] A. Testing of optical constants.

[0099] 1) Adjust the polarizer angle to 0° using motor control. The 0° position of the polarizer is the position when the polarizer's transmission vibration direction is perpendicular to the incident surface; adjust the analyzer angle to 0°.

[0100] 2) Push the compensator in, turn on the power to the compensator motor, and make it rotate at a constant speed along the optical axis at a specific speed.

[0101] 3) Use a computer-controlled monochromator to change the wavelength of the incident beam in a certain step size and obtain the light intensity signal through CMOS.

[0102] 4) Because the compensator rotates periodically, the light intensity signal detected by the CMOS camera also exhibits periodic changes. Using the CMOS camera as the detector, the detected light intensity *i* over time *t* can be expressed as:

[0103] ;

[0104] in, i(t) The light intensity measurement value of the harmonic signal. This represents the DC component of the light intensity harmonic signal. and The Fourier coefficients represent the normalized Fourier coefficients of the measured light intensity signal. ω is the initial azimuth angle of the compensator, and ω is the angular frequency of the continuous rotation of the hollow motor that drives the compensator.

[0105] 5) By performing Fourier analysis on the measured light intensity signal, the relationship between the measured Fourier coefficients and the normalized Fourier coefficients can be obtained. By analyzing these Fourier coefficients, the ellipsometric parameters of the sample can be solved, which can be expressed as:

[0106] ;

[0107] ;

[0108] ;

[0109] ;

[0110] In the above formula, P is the angle between the polarizer's transmission direction and the incident plane; A is the angle between the analyzer's transmission direction and the incident plane; Ψ and Δ are ellipticity parameters. The incident angle is the angle between the incident polarized light and the sample normal, as mentioned above.

[0111] 6) The ellipsometric parameters Ψ and Δ of the sample under test can be obtained through the above analysis. Then, by inverting and fitting the ellipsometric parameters, the optical constants of the sample can be obtained. The inversion and fitting process is as follows: a theoretical model is established based on the sample structure, including the refractive index of the substrate and each thin film layer, as well as the thickness of the thin film; the theoretical ellipsometric parameters corresponding to different parameters in the model are calculated using optical theories (such as the Fresnel equation); the parameters in the model are adjusted using optimization algorithms (such as the least squares method) to minimize the difference between the theoretical and experimentally measured ellipsometric parameters. This process needs to be iterated until the optimal fitting parameters are found, and the accuracy of the model is evaluated by calculating the fitting residuals.

[0112] 7) Treat each pixel of the CMOS camera as a micro-region, and repeat the above processing on the detected light intensity to obtain the optical constant of any micro-region of the sample.

[0113] B. Testing of magneto-optical parameters.

[0114] 1) Push out the compensator and the motor that controls the rotation of the compensator.

[0115] 2) By controlling the motor, adjust the polarizer angle to 90°. By observing the CMOS camera and rotating the polarizer, the light intensity is reduced to the minimum. This is the extinction position. Record the polarizer angle as X at this time.

[0116] 3) Use software to control the magnitude of the electromagnet's magnetic field so that the sample's positive magnetic field is saturated.

[0117] 4) Controlled by a motor, the polarizer is rotated incrementally around center X, within the range of X-10 degrees and X+10 degrees, in 1° increments. At each angle, the analyzer is controlled to rotate from 80° to 100°, in 1-degree increments. The angles between the polarizer and analyzer are denoted as follows: and The light intensity value detected by CMOS is recorded at each set of polarizer and analyzer angles, and the light intensity value at each set of angles is denoted as I+. The step interval of the polarizer and analyzer can be 3°, 1° or 0.5°, etc., and an appropriate sampling interval can be selected according to the magnitude of the magneto-optical signal of the sample.

[0118] 5) Use software to control the magnitude of the electromagnet's magnetic field, saturating the sample's reverse magnetic field. Repeat the previous step, recording the light intensity value I- at each angle.

[0119] 6) Based on the Jones matrices of the polarizer, analyzer, and detector, and neglecting the second-order terms of all magneto-optical coupling coefficients, the light intensity detected by the detector can be expressed as:

[0120] ;

[0121] To simplify the expression, the following definition is made:

[0122] ;

[0123] ;

[0124] ;

[0125] ;

[0126] ;

[0127] ;

[0128] ;

[0129] ;

[0130] ;

[0131] ;

[0132] ;

[0133] In the above formula, r p The normalized p-complex reflectance, For coefficients, , , Let represent the magnetostrictive reflection coefficients caused by the transverse, longitudinal, and poloidal Kerr effects, respectively. The reflection coefficient of the material in its unmagnetized state; Indicates taking the real part, This indicates taking the transpose of the matrix.

[0134] 7) The rate of change of light intensity can be expressed as:

[0135] ;

[0136] 8) As shown in the above equation, the rate of change of light intensity is a function of θ1 and θ2. Therefore, by changing θ1 and θ2 multiple times and measuring multiple sets of ΔI, the parameters B1-B8 can be solved through inversion fitting, and thus the reflectance coefficient can be obtained. and magneto-reflection coefficient , , The magneto-optical coupling coefficient Q can then be calculated using the following formula:

[0137] ;

[0138] ;

[0139] ;

[0140] ;

[0141] When the material being measured is a magnetic material, then:

[0142] ;

[0143] When the material being measured is a thin film material with one and only one magnetic layer, then:

[0144] ;

[0145] Among them, N0, N i N sub They are air, the first i The refractive index of the thin film and the substrate; d i Let be the thickness of the i-th thin film; φ0 and φ i Let be the angle of incidence of light and the angle of refraction when the light enters the i-th layer; This represents the magneto-reflection coefficient caused by the poloidal Kerr effect; The reflection coefficient of the material in its unmagnetized state; The reflection coefficient is the ratio of the incident S-ray to the reflected S-ray. Let be the magneto-optical coupling coefficient of the i-th thin film.

[0146] When the material being measured is a thin film material with multiple magnetic layers, fitting is required to solve it.

[0147] 9) In the process of solving Q, there will be two mutually conjugate solutions. At this time, it is necessary to select the solution that conforms to the physical reality based on the basic properties of the sample.

[0148] C. Magnetic domain observation.

[0149] 1) Push out the compensator and the motor that controls the rotation of the compensator.

[0150] 2) By controlling the motor, adjust the analyzer angle to 0°. By observing the CMOS camera and rotating the polarizer, the light intensity is reduced to the minimum. This is the extinction position, denoted as Y.

[0151] 3) Adjust the polarizer angle slightly off the Y position using motor control. Typically, a suitable adjustment angle needs to be selected based on the magnitude of the sample's reflected signal; in this embodiment, an adjustment of 0.1 degrees is chosen.

[0152] 4) By controlling the electromagnet with software, the magnetic field strength can be adjusted to the magnetic field strength at the beginning of magnetization, and the process of magnetization of the sample can be observed in CMOS.

[0153] The above methods are used for measurement and analysis to further verify the superiority of the proposed solution in this embodiment.

[0154] First, the incident light source is set as an ideal Gaussian beam, and the homogenization effect of the homogenization and shaping module and its impact on the ellipticity test results are compared. For example... Figure 3 The intensity distributions of the incident ideal Gaussian beam and the uniform beam after homogenization shown in (a) are used to more intuitively compare the differences in uniformity between the two light sources. The flat-top factor is calculated as an evaluation parameter. Figure 3 As shown in (b), the flat-top factors before and after light homogenization of the light source are 0.4463 and 0.8780, respectively, which further demonstrates that the optimized light source has better uniformity.

[0155] Secondly, simulation calculation Figure 3The ellipticity parameters and Kerr deflection angles were measured under two different light source illumination conditions. The simulated material was a 200 nm thick Fe thin film grown on a silicon substrate, with a wavelength range of 400-700 nm. In the simulation, it was assumed that the average magnitude of all noise was 1% of the maximum irradiance. Under this condition, the signal-to-noise ratio (SNR) of Gaussian illumination varied between 13 and 20 dB, while the SNR of uniform irradiance obtained through an integrating lens array was mostly greater than 19 dB. The simulation results of the sample test error and the noise-free ideal value at a wavelength of 650 nm are shown below. Figure 4 As shown, Ψ and Δ are elliptic deflection parameters. The rotation angle is deg, which represents degrees, and mrad, which represents milliradians. Clearly, the spatial distribution of the absolute value of the test error is better after the light source passes through the uniform light shaping module.

[0156] Finally, as Figure 5 As shown in (a) to (h), images of the continuous changes in a strip-shaped magnetic domain in a Co-based magnetic heterostructure were obtained through continuous data acquisition under continuously changing magnetic field conditions. The field of view was 1 mm × 1 mm, and the acquisition time was 4 seconds. To highlight the magnetic domain pattern, the images were colored after data processing, with red representing the magnetization direction facing outward and cyan representing the magnetization direction facing inward. This method enables effective observation and analysis of magnetic domain changes.

[0157] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. A micro-region magneto-optical parameter, optical constant and magnetic domain comprehensive testing and analyzing system, characterized in that, The application relates to a kind of systems and methods for measuring magnetic domain changes of sample, comprising: A light source module for emitting parallel light beams; A homogenizing shaping module for compensating incident parallel light beams and outputting uniform parallel light beams; A polarization modulation module for deflecting uniform parallel light beams to generate linearly polarized light, and modulating the polarization state of linearly polarized light to generate approximately linearly polarized light with high polarization state and detect polarization; An electromagnet sample stage for placing a sample to be tested and adjusting the magnetic field environment of the sample to be tested; An imaging detection module for collecting light intensity signals after the sample to be tested and converting them into image data; A control and analysis module for controlling the operation of each module, calculating the optical constants, magneto-optical parameters and dynamic observation of magnetic domain changes of the sample to be tested according to the collected light intensity signals and image data.

2. The micro-magnetic-optical parameter, optical constant and magnetic domain comprehensive testing and analyzing system of claim 1, wherein, The light source module comprises a light source, a monochromator, a fiber adapter, an incident fiber and a first collimating lens arranged in sequence; The light outlet of the light source is aligned with the light inlet of the monochromator, the divergent light beam output by the light source is incident into the monochromator to generate monochromatic light beams with a set wavelength; The light outlet of the monochromator is provided with the fiber adapter, the fiber adapter is connected with the light receiving end of the incident fiber, and a lens pair is installed in the fiber adapter to converge the divergent monochromatic light beams generated by the monochromator to the light receiving end of the incident fiber; The light output end of the incident fiber is connected with the collimating lens, the divergent light output by the incident fiber is collimated through the first collimating lens, and the collimated parallel light beams are incident into the homogenizing shaping module.

3. The micro-magnetic-optical parameter, optical constant and magnetic domain comprehensive testing and analyzing system of claim 2, wherein, The angle and position between the light outlet of the light source and the light inlet of the monochromator are adjusted, so that: At the end of the system, a light power meter and a spectrum analyzer are arranged; The power of the received light intensity signal is measured by the light power meter, the distance between the light outlet of the light source and the light inlet of the monochromator is continuously adjusted, and the power of the light intensity signal measured by the light power meter is maximized; The light intensity signal is analyzed by the spectrum analyzer, the angle between the light outlet of the light source and the light inlet of the monochromator is continuously adjusted, and the light intensity signal analyzed by the spectrum analyzer has optimal monochromaticity.

4. The micro-magnetic-optical parameter, optical constant and magnetic domain comprehensive testing and analyzing system of claim 1, wherein, The homogenizing shaping module comprises a first integrating lens, a second integrating lens and a condenser lens arranged in sequence, and the second integrating lens is located at the back focal plane of the first integrating lens; The incident parallel light beams are divided into a plurality of secondary wave sources by the first integrating lens array, and the secondary wave sources are superimposed by the second integrating lens array and the condenser lens to compensate for the non-uniformity of the secondary wave sources at the symmetrical positions, and uniform light beams are output.

5. The micro-magnetic-optical parameter, optical constant and magnetic domain comprehensive testing and analyzing system of claim 1, wherein, The polarization modulation module comprises a second collimating lens, a polarizer, a compensator and an analyzer arranged in sequence; wherein the polarizer and the analyzer are both Glauber prisms and are respectively installed on a micro rotary motor; the compensator is a 1 / 4 wave plate installed in a push-pull device and connected with the motor; ​ The incident uniform light beam is first collimated by a second collimating lens, and then deflected by a polarizer to emit linearly polarized light. The linearly polarized light is subjected to polarization state modulation by a 1 / 4 wave plate serving as a compensator, and two polarization components perpendicular to each other in vibration direction are subjected to phase delay of 1 / 2 and combined into elliptically polarized light. The elliptically polarized light is then incident on an analyzer to be analyzed. ​ 6. The micro-magnetic-optical parameter, optical constant and magnetic domain comprehensive testing and analyzing system of claim 5, wherein, An electromagnet sample stage is arranged between the compensator and the polarizer, and the electromagnet sample stage comprises a single-pole electromagnet and a sample stage; the sample stage is used for placing a sample to be tested, and the single-pole electromagnet is used for adjusting the size of the magnetic field in which the sample to be tested is located. The imaging detection module comprises a microscopic imaging unit and a CMOS camera, and the microscopic imaging unit and the CMOS camera are arranged before and after the polarizer respectively; the microscopic imaging unit is used for amplifying light intensity signals, and the unit comprises a microscopic objective lens and an imaging lens, the microscopic objective lens has a long working distance and achromaticity, and the imaging lens has achromaticity; the CMOS camera is used for detecting light intensity signals and converting them into image data.

7. A method for comprehensive testing and analysis of micro-region magneto-optical parameters, optical constants and magnetic domains, characterized in that, The micro-region magneto-optical parameter, optical constant and magnetic domain comprehensive test analysis system based on any one of claims 1-6 realizes dynamic observation of optical constant, magneto-optical parameter and magnetic domain change in the same micro-region in the next test; wherein the test process of the optical constant is: The polarizer angle is controlled to 0°, and the analyzer angle is controlled to 0°; The push-pull device is driven to push the compensator, the compensator is controlled to rotate at a set speed along the optical axis, and the monochromator is controlled to change the wavelength of the incident light beam according to a set step; Each pixel of the CMOS camera is taken as a micro-region, the light intensity signal of each micro-region is detected, the ellipsometric parameters of the sample to be measured are obtained by Fourier analysis, and the optical constants of the sample to be measured are obtained by inversion fitting of the ellipsometric parameters.

8. The method of claim 7, wherein the micro-magnetic-optical parameters, optical constants and magnetic domain are integrated and analyzed. The test process of the magneto-optical parameter is: ​ The push-pull device is driven to push the compensator out, the analyzer angle is controlled to 90°, the light intensity signal is adjusted to the minimum by observing the imaging of the CMOS camera and rotating the polarizer, and the initial polarizer angle X is recorded; The magnetic field size of the electromagnet is adjusted to saturate the forward magnetic field of the sample to be measured; With the initial polarizer angle X as the center, the polarizer is rotated step by step in a set range according to a set step, and at each angle, the control analyzer is rotated according to a set step, and the polarizer and analyzer angles are recorded as and and the light intensity value I+ detected by the CMOS is recorded at each group of deflection angles. The magnetic field size of the electromagnet is adjusted to saturate the reverse magnetic field of the sample to be measured, the deflection steps of the polarizer and the analyzer are repeated, and the light intensity value I- detected by the CMOS camera is recorded under each deflection angle; According to the Jones matrix detected by the polarizer, the analyzer and the CMOS camera, the relationship between the light intensity and the deflection angle is analyzed, the reflection coefficient and the magnetic reflection coefficient are obtained by inversion fitting according to the light intensity values measured under multiple deflection angles, and the magneto-optical coupling coefficient is calculated.

9. The method for comprehensive testing and analysis of micro-area magneto-optical parameters, optical constants, and magnetic domains as described in claim 7, characterized in that, The process of observing the magnetic domain is: The analyzer angle is controlled to 0°, the light intensity signal is adjusted to the minimum by observing the imaging of the CMOS camera and rotating the polarizer, and the initial polarizer angle Y is recorded; According to the set deflection angle, the initial polarizer angle Y is adjusted, the magnetic field size of the electromagnet is adjusted to the initial magnetization magnetic field strength, and the magnetization process of the sample to be measured is observed in the CMOS camera.

10. The method for comprehensive testing and analysis of micro-area magneto-optical parameters, optical constants, and magnetic domains as described in claim 7, characterized in that, Before synchronously testing the optical constant and the magneto-optical parameter and dynamically observing the magnetic domain change, the preparation work is carried out in advance, including: Preheat the electromagnet; Turn on the power supply of the light source, the monochromator, the control and analysis module and the CMOS camera; Adjust the incident angle of the support, which is the included angle between the incident light and the normal line of the sample to be measured; Place the sample to be measured on the electromagnet sample table, adjust the position of the sample to be measured so that the upper surface of the sample is located at the center of the electromagnet magnetic pole, and the reflected light is incident from the center of the support and is coaxial with the analyzer module; Move the microscopic imaging unit forward and backward along the optical axis, adjust the working distance so that the CMOS camera can detect a clear image, and adjust the power of the light source to avoid saturation of the CMOS camera.

Images