Multifunctional micro-area magneto-optical system based on inserted rod type superconducting magnet and test method

Abstract

The invention discloses a multifunctional micro-area magneto-optical system based on an inserted rod type superconducting magnet and a test method. The system comprises the inserted rod type superconducting magnet (10); the mechanical supporting module is used for bearing the insertion rod type superconducting magnet (10), the MOKE and RMCD module (7), the ultra-long-distance inverted microscopic imaging module (8) and the low-temperature sample rod and light path coupling module (9); an ultra-long distance inverted microscopic imaging module (8); one end of the low-temperature sample rod and light path coupling module (9) extends into the inserted rod type superconducting magnet (10) to bear a sample to be tested, and the other end of the low-temperature sample rod and light path coupling module (9) is respectively in light path connection with the MOKE and RMCD module (7) and the ultra-long-distance inverted microscopic imaging module (8); and an electric control and software control module. According to the invention, synchronous measurement of MOKE and RMCD under a strong magnetic field is realized, functions of PL, Raman and the like can be expanded, micro-area magneto-optical automatic in-situ comprehensive test under a 1.5-300K variable-temperature environment with a spatial resolution of 1 [mu] m is achieved, and key technical support is provided for research on spin characteristics of magnetic materials.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of micro-area photoelectric testing under low-temperature magnetic field, and more particularly to a multifunctional micro-area magneto-optical system based on a pole-inserted superconducting magnet and a testing method. BACKGROUND

[0002] The multifunctional micro-area magneto-optical system based on a pole-inserted superconducting magnet is an advanced scientific research instrument integrating a strong magnetic field environment and high-precision optical detection. The system core adopts a pole-inserted superconducting magnet as a magnetic field generating device, which can generate a strong steady magnetic field of up to 16 tesla. Through a specially designed pole structure and an integrated optical measurement module, synchronous measurement of magneto-optical Kerr effect (MOKE) and reflective magnetic circular dichroism (RMCD) with micron-level spatial resolution is realized. At the same time, the system can expand micro-area magneto-optical measurement functions such as photoluminescence (PL), fluorescence lifetime imaging microscopy (FLIM), Raman spectroscopy (Raman), and second harmonic generation (SHG).

[0003] MOKE and RMCD describe that when linearly polarized light irradiates the surface of a magnetic material, due to the difference in propagation rate and absorption rate of right circularly polarized light and left circularly polarized light in the magnetic sample, a phase difference and amplitude difference are generated, and the outgoing light is elliptically polarized light with angular polarization conversion. By monitoring the change of the angle (MOKE) and the elliptical polarization degree (RMCD) signal with the magnetic field, the magnetic hysteresis loop can be measured. It can be used to observe and measure the Kerr rotation angle, the coercive field, the Curie temperature, the exchange bias field, and other information of the sample, and can also be used to observe the magnetic domain and magnetization process of the sample. The pole-inserted superconducting magnet system can further expand the functions of PL, FLIM, Raman, and SHG, and can comprehensively analyze the electronic energy level structure, luminescence lifetime, lattice vibration, and symmetry of materials in a strong magnetic field environment, realizing precise measurement of micro-area magnetic field-optical- low-temperature multi-physical field coupling.

[0004] In the current technical background, with the in-depth research of nanotechnology and low-dimensional materials, researchers have an increasing demand for characterization of magnetic properties at micro-nano scale. Traditional magneto-optical measurement systems mainly use electromagnets or permanent magnets, but their magnetic field strength is usually limited to below 2 Tesla, and it is difficult to integrate with low-temperature environment. Superconducting magnets can provide strong magnetic fields, but traditional wet superconducting magnets have problems such as large consumption of liquid helium and high vibration noise. The plug-in rod type dry superconducting magnet has become the mainstream technical solution, which integrates optical components and low-temperature sample rods that can be inserted into the interior of the magnet, realizing a strong magnetic field micro-optical measurement system. Commercial integrated measurement systems such as Quantum Design's PPMS system have realized the integration of Raman and photoluminescence measurement functions with variable temperature magnetic fields, but the micro-space resolution and multi-mode optical measurement capability still need to be improved, and the function expansion lacks modularization and standardization interface. Therefore, developing an integrated system based on plug-in rod type superconducting magnet with high strength magnetic field, high spatial resolution and multi-mode optical measurement capability is one of the important technical problems to be solved in the field of magnetic measurement. SUMMARY

[0005] In view of the above defects or improvement needs of the prior art, the present application is a multifunctional micro-region magneto-optical system based on a plug-in rod type superconducting magnet and a test method. By using a plug-in rod type superconducting magnet, integrating MOKE and RMCD modules, ultra-long distance inverted microscopic imaging modules, low-temperature sample rods and optical coupling modules, and matching multi-channel control power supply, piezoelectric scanning table and other electric control components with full-automatic control software, synchronous measurement of MOKE and RMCD under strong magnetic field is realized, PL, Raman and other functions can be expanded, 1 μm level spatial resolution, 1.5K-300K variable temperature environment micro-region magneto-optical automatic in-situ comprehensive test is achieved, and key technical support is provided for spin characteristic research of magnetic materials.

[0006] In order to achieve the above purpose, according to the first aspect of the present application, a multifunctional micro-region magneto-optical system based on a plug-in rod type superconducting magnet is provided, comprising: The plug-in rod type superconducting magnet is used for providing a strong magnetic field test environment for a sample to be tested; the mechanical support module is used for bearing the plug-in rod type superconducting magnet, the MOKE and RMCD module, the ultra-long distance inverted microscopic imaging module and the low-temperature sample rod and optical path coupling module; the MOKE and RMCD module is used for synchronously measuring a magneto-optical Kerr effect (MOKE) signal and a reflective magneto-optical circular dichroism (RMCD) signal of the sample; the ultra-long distance inverted microscopic imaging module is used for sample real space imaging and positioning; the low-temperature sample rod and optical path coupling module has one end extending into the plug-in rod type superconducting magnet to bear the sample to be tested and the other end respectively forming optical path connection with the MOKE and RMCD module and the ultra-long distance inverted microscopic imaging module; the electric control and software control module is electrically connected with each module to realize full-process automation of sample positioning, magnetic field adjustment, temperature control, optical path switching and data acquisition and analysis, and the micro-area optical path light spot does not deviate in the optical path switching process.

[0007] Further, the mechanical support module comprises adjustable rubber shock-absorbing foot cups, a bottom plate, bottom stainless steel support columns, a support panel, stainless steel support columns and a breadboard; the adjustable rubber shock-absorbing foot cups are arranged at the bottom of the bottom plate; one end of the bottom stainless steel support columns is fixedly connected with the bottom plate, and the other end is fixedly connected with the support panel; one end of the stainless steel support columns is fixedly connected with the support panel, and the other end is fixedly connected with the breadboard; the MOKE and RMCD module and the ultra-long distance inverted microscopic imaging module are arranged on the breadboard.

[0008] Further, the MOKE and RMCD module comprises a laser light source, a first achromatic lens, a mirror, a second achromatic lens, a polarization beam splitter prism, a first 1 / 2 wave plate, a first Glan-Tomson prism, a second 1 / 2 wave plate, a beam splitting element, a third mirror, a photoelastic modulator, a chopper, a first electric switching motor and a mirror, a second Glan-Tomson prism, a third achromatic lens, a balanced amplifier, a lock-in amplifier and a spectrometer, wherein: the first achromatic lens and the second achromatic lens constitute an expansion beam assembly, which expands the laser light exiting the free optical path by three times and reduces the divergence angle thereof, so that the laser light is focused to the spot size reaching the diffraction limit when focused on the sample, thereby enhancing the spatial resolution of the micro-area two-dimensional scanning test; the first Glan-Tomson prism and the second Glan-Tomson prism have a high extinction ratio of 100000:1, which significantly reduces the interference of stray light and background noise and improves the signal-to-noise ratio of weak signals, and the system can detect a Kerr angle resolution of 1 mdeg; the first Glan-Tomson prism is incident at an angle of 45° with respect to the optical axis of the photoelastic modulator, and the light is modulated into a sinusoidal wave of 50 MHz, so that the linearly polarized light changes in the linear-left-handed-linear-right-handed-linear polarization state in a very short period, the chopper modulates the light into a rectangular wave of hundreds of hertz, the signal light is focused on the balanced amplifier through the second Glan-Tomson prism and the third achromatic lens to be converted into a voltage signal, and the photoelastic modulator, the chopper and the balanced amplifier are all connected with the lock-in amplifier; the signal of the chopper frequency is the light intensity change information, and the signal of the photoelastic modulator frequency carries the information of the light intensity and polarization change, and the two divided by each other can obtain the pure MOKE and RMCD signals; the first electric switching motor and the mirror cooperate with the mirror and the spectrometer to realize various photoelectric tests under the low-temperature magnetic field based on the plug-in superconducting magnet, including but not limited to the micro-area photoelectric tests such as PL, Raman and SHG under the low-temperature magnetic field.

[0009] Further, the super-long distance inverted microscopic imaging module comprises an LED white light source, a fourth achromatic lens, a fifth mirror, a fifth achromatic lens, a second electric switching motor and a beam splitter, a sixth achromatic lens and a CMOS camera; the illumination light source passes through the beam splitter, passes through the low-temperature sample rod and the optical path coupling module, the low-temperature sample rod and the optical path coupling module comprise a relay lens, and the length of the micro-area Kohler illumination light path system is extended, the imaging area of the long-distance Kohler illumination system is about 120 um, and the piezoelectric module of the sample rod can quickly realize the micro-area electric sample finding under the low-temperature magnetic field; when the target sample is found, the electric switching motor and the beam splitter cut into the light path to realize the simultaneous observation of the laser spot and the micro-area sample, and when the test is performed, the electric switching motor and the beam splitter cut out of the light path and the spot does not deviate, thereby ensuring the high efficiency of the sample signal collection.

[0010] Further, the low-temperature sample rod and the optical path coupling module are internally provided with a relay lens, which is used to extend the length of the Kohler illumination system in the ultra-long distance inverted microscopic imaging module, and realize long-distance optical path transmission.

[0011] Further, the electric control and software control unit comprises a multi-path control power supply, a variable speed handle, an XYZ axis piezoelectric scanning table, an electric switching motor, an electric rotating motor, a temperature controller and a PWM signal generator; the XYZ axis piezoelectric scanning table is arranged on the low-temperature sample rod and the optical path coupling module, and is used to drive the sample to be tested to realize micro-area scanning; the temperature controller is used to control the temperature of the low-temperature sample rod and the optical path coupling module, so as to realize the temperature change environment of the sample to be tested; the multi-path control power supply is used to provide excitation current for the plug-in rod type superconducting magnet, and adjust the magnetic field strength; the software control module realizes one-key switching of the optical path mode through a preset program.

[0012] Further, the plug-in rod type superconducting magnet can generate a maximum steady-state magnetic field strength of 16 tesla; the temperature controller in the electric control and software control unit has a temperature control range of 1.5K-300K, and can realize temperature regulation of the sample to be tested from low temperature to room temperature.

[0013] Further, the XYZ axis piezoelectric scanning table in the electric control and software control unit cooperates with the MOKE and RMCD modules to realize micron-level micro-area magnetic domain scanning of the sample to be tested, and the system has a spatial resolution of about 1μm; the system has a Kerr angle resolution of 1mdeg, and can detect weak magneto-optical signals.

[0014] Further, the spectrometer cooperates with the first electric switching motor and the reflector to realize micro-area photoelectric testing of photoluminescence (PL), Raman and second harmonic generation (SHG) of the sample to be tested.

[0015] According to the second aspect of the present application, a kind of magnetic material micro-area magnetism and extended photoelectric characteristic step-by-step testing method is provided, and it is realized by the multifunctional micro-area magneto-optical system based on plug-in rod type superconducting magnet, comprising: S100: check system core component connection and state, load the magnetic sample of adaptive size and fix alignment, pre-check microscopic imaging and detection link unobstructed; S200: start superconducting magnet refrigeration and stabilize to target temperature, initialize magnetic field to required value, adjust laser light path and start photoelastic modulator and other detection modules to complete calibration; S300: start microscopic imaging mode, move sample by two-dimensional piezoelectric table to select target micro-area, fine-tune to ensure that laser spot covers target area, then cut out beam splitter to avoid optical path interference; S400: set MOKE and RMCD test parameters in control software, collect signals with standard sample with known magnetism parameters and calculate calibration coefficient; S500: Adjust the magnetic field by a set magnetic field step to synchronously collect the MOKE and RMCD signals, and complete the micro-region magnetic domain scanning and record data by driving the sample through the two-dimensional piezoelectric stage under multiple fixed magnetic fields; S600: Switch the light path to the PL / Raman mode through software, adjust the spectrometer parameters, and collect the extended spectrum signals of the sample under different magnetic fields and temperatures; S700: Save the test data and generate the results through the analysis module, gradually demagnetize, turn off the power supply of each module of the system, take out the sample, clean the components, and make a good record of the use of the equipment.

[0016] Overall, compared with the prior art, the above technical solutions conceived by the present application can achieve the following beneficial effects: 1. The system of the present application combines high magnetic field and high spatial resolution to realize multifunctional synchronous measurement. The system uses a plug-in rod type superconducting magnet to provide a strong and stable magnetic field of up to 16 tesla, and can synchronously obtain MOKE and RMCD signals under magnetic field scanning. It can realize micron-level high spatial resolution magnetic domain scanning by fixing different magnetic fields, analyze the spin characteristics of magnetic materials from multiple angles, including but not limited to temperature, electric field and stress control methods, and provide key technical support for the study of multi-dimensional controlled magnetic domain structure and dynamics at micro / nano scale.

[0017] 2. The system of the present application has high compatibility and automatic operation characteristics. Through modular design, the system has good functional expandability and can be compatible with multiple optical measurement modes: including but not limited to PL, Raman, SHG and magneto-optical Kerr microscope under low temperature magnetic field, supporting in-situ and synchronous comprehensive analysis of the magnetic, optical and electronic characteristics of materials under strong magnetic field and variable temperature (1.5K-300K) environment, greatly improving the research efficiency and data correlation. Combined with fully automatic control software, the whole process automation from sample positioning, data acquisition to analysis is realized, including but not limited to electric piezoelectric stage, light source control, light path electric switching, temperature control, magnetic field control, data acquisition and analysis, etc., which significantly reduces the operation difficulty, improves the repeatability and reliability of the measurement. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 Fig. 1 is a structural schematic diagram of a multifunctional micro-region magneto-optical system based on a plug-in rod type superconducting magnet according to an embodiment of the present application; Figure 2 Fig. 2 is a schematic diagram of MOKE and RMCD light paths according to an embodiment of the present application; Figure 3 Fig. 3 is a schematic diagram of an ultra-long distance inverted microscopic imaging module light path according to an embodiment of the present application; Figure 4 Fig. 4 is a test diagram of a multifunctional micro-region magneto-optical system based on a plug-in rod type superconducting magnet according to an embodiment of the present application; Figure 5 MOKE and RMCD hysteresis loop diagram of CoFeB film at 300K temperature of the embodiment of the application; Figure 6 Flow chart of the step-by-step test method of the magnetic material micro-region magnetism and the extended photoelectric characteristics based on the multi-functional micro-region magneto-optical system of the pole-inserted superconducting magnet of the embodiment of the application.

[0019] In all the drawings, the same reference signs represent the same technical features, specifically: 1-adjustable rubber shock-absorbing foot cup, 2-bottom plate, 3-bottom stainless steel support column, 4-supporting panel, 5-stainless steel support column, 6-breadboard, 7-MOKE and RMCD module, 8-ultra-long distance inverted microscopic imaging module, 9-low-temperature sample rod and optical path coupling module, 10-pole-inserted superconducting magnet, 11-laser light source, 12-first achromatic lens, 13-first reflecting mirror, 14-second achromatic lens, 15-polarizing beam splitter prism, 16-first 1 / 2 wave plate, 17-first Glan-Tromson prism, 18-second reflecting mirror, 19-second 1 / 2 wave plate, 20-beam splitting element, 21-third reflecting mirror, 22-photoelastic modulator, 23-chopper, 24-first electrically switchable motor and reflecting mirror, 25-second Glan-Tromson prism, 26-third achromatic lens, 27-balanced amplifier, 28-phase-locked amplifier, 29-fourth reflecting mirror, 30-spectrometer, 31-LED white light source, 32-fourth achromatic lens, 33-fifth reflecting mirror, 34-fifth achromatic lens, 35-second electrically switchable motor and beam splitter mirror, 36-sixth achromatic lens, 37-CMOS camera. DETAILED DESCRIPTION

[0020] In order to make the objectives, technical solutions and advantages of the present application clearer, the present application will be further described in details below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and should not be used to limit the present application. In addition, the technical features involved in each embodiment of the present application described below can be combined with each other as long as they do not conflict with each other.

[0021] As Figure 1As shown, the system comprises a plug-in rod superconducting magnet 10, a mechanical support module, a MOKE and RMCD module 7, an ultra-long distance inverted microscopic imaging module 8, a low-temperature sample rod and light path coupling module 9, and an electric control and software control module. The plug-in rod superconducting magnet 10 can generate a maximum steady-state magnetic field strength of 16 tesla; the mechanical support module comprises an adjustable rubber shock-absorbing foot cup 1, a bottom plate 2, a bottom stainless steel support column 3, a support panel 4, a stainless steel support column 5, and a breadboard 6; the adjustable rubber shock-absorbing foot cup 1 is arranged at the bottom of the bottom plate 2; one end of the bottom stainless steel support column 3 is fixedly connected with the bottom plate 2, and the other end is fixedly connected with the support panel 4; one end of the stainless steel support column 5 is fixedly connected with the support panel 4, and the other end is fixedly connected with the breadboard 6; the MOKE and RMCD module 7 and the ultra-long distance inverted microscopic imaging module 8 are both arranged on the breadboard 6. The MOKE and RMCD module 7 comprises a laser light source 11, a first achromatic lens 12, a first reflecting mirror 13, a second achromatic lens 14, a polarization beam splitter prism 15, a first 1 / 2 wave plate 16, a first Glan-Tomson prism 17, a second 1 / 2 wave plate 19, a beam splitting element 20, a third reflecting mirror 21, a photoelastic modulator 22, a chopper 23, a first electrically-driven switching motor and reflecting mirror 24, a second Glan-Tomson prism 25, a third achromatic lens 26, a balanced amplifier 27, a lock-in amplifier 28, and a spectrometer 30. The ultra-long distance inverted microscopic imaging module 8 comprises an LED white light source 31, a fourth achromatic lens 32, a fifth reflecting mirror 33, a fifth achromatic lens 34, a second electrically-driven switching motor and beam splitter 35, a sixth achromatic lens 36, and a CMOS camera 37. The low-temperature sample rod and light path coupling module 9 is internally provided with a relay lens, which is used to extend the length of the Kohler illumination system in the ultra-long distance inverted microscopic imaging module 8, so as to realize long-distance light path transmission. The electric control and software control unit comprises a multi-path control power supply, a variable-speed handle, an XYZ-axis piezoelectric scanning table, an electrically-driven switching motor, an electrically-driven rotating motor, a temperature controller, and a PWM signal generator; the XYZ-axis piezoelectric scanning table is arranged on the low-temperature sample rod and light path coupling module 9, and is used to drive the sample to be measured to realize micro-area scanning; the temperature controller is used to control the temperature of the low-temperature sample rod and light path coupling module 9, so as to realize the temperature variation environment of the sample to be measured; the multi-path control power supply is used to provide excitation current for the plug-in rod superconducting magnet 10, so as to adjust the magnetic field strength; the software control module realizes one-key switching of the light path mode through a preset program. The temperature control range of the temperature controller in the electric control and software control unit is 1.5K-300K, and the temperature of the sample to be measured can be controlled from low temperature to room temperature.

[0022] The system of the application can isolate external vibration through shock absorption and rigid support design, guarantee the installation precision of components and the stability of light path, and lay a foundation for accurate data collection; can provide a maximum of 16 tesla strong steady-state magnetic field and a variable temperature environment of 1.5K-300K, meet the research needs of material multi-physical field characteristics; has a 1mdeg Kerr angle resolution and a 1μm micro-area spatial resolution, can obtain pure MOKE and RMCD signals to accurately measure magnetic parameters; can also simultaneously carry out MOKE and RMCD tests, expand the micro-area photoelectric test functions of PL and Raman, etc., realize accurate positioning of the sample by matching an ultra-long distance inverted microscopic imaging module, and rely on an electric control module and software support to realize full-process automatic operation, thereby simplifying the operation difficulty and improving the test repeatability and research efficiency.

[0023] As Figure 2As shown, the laser light source 11 is expanded by the first achromatic lens 12 and the second achromatic lens 14, passes through the polarization beam splitter 15, and then passes through the first Glan-Tomson prism 17 after the laser light passes through the corresponding first 1 / 2 wave plate 16. After being reflected by the second mirror 18, the excitation light is reflected to the low-temperature sample rod and the optical coupling module 9 and finally focused on the sample. The sample signal passes through the beam splitting element 20, the third mirror 21, the photoelastic modulator 22, the chopper 23 and the second Glan-Tomson prism 25 in turn, and finally is focused on the balanced amplifier 27 by the third achromatic lens 26. The signal value is read by the lock-in amplifier 28 to realize the measurement of the micro-area magneto-optical Kerr effect. The first electrically switchable motor and the mirror 24 are switched to the right side, and the fourth mirror 29 reaches the spectrometer 30 to realize the micro-area PL, Raman, SHG and other related measurement functions. The system light path mode switching can be controlled by software one-key and the micro-area light path spot does not deviate. The first achromatic lens 12 and the second achromatic lens 14 form an expansion assembly, which expands the laser light emitted from the free light path by three times to reduce its divergence angle, so that the laser light is focused on the sample to reach the diffraction limit spot size, thereby enhancing the spatial resolution of the micro-area two-dimensional scanning test. The first Glan-Tomson prism 17 and the second Glan-Tomson prism 25 have a high extinction ratio of 100000:1, which significantly reduces the interference of stray light and background noise and improves the signal-to-noise ratio of weak signals. The system can detect the Kerr angle resolution of 1mdeg. The first Glan-Tomson prism 17 is incident at a 45° angle relative to the optical axis of the photoelastic modulator 22 to modulate the light into a 50MHz sine wave. The linearly polarized light changes in linear-left-handed-linear-right-handed-linear polarization state in a very short period. The chopper 23 modulates the light into a 100Hz rectangular wave. The signal light is focused on the balanced amplifier 27 by the second Glan-Tomson prism 25 and the third achromatic lens 26 to be converted into a voltage signal. The photoelastic modulator 22, the chopper 23 and the balanced amplifier 27 are connected with the lock-in amplifier 28. The frequency signal of the chopper 23 carries the information of light intensity change, and the frequency signal of the photoelastic modulator 22 carries the information of light intensity and polarization change. The two divided by each other can obtain pure MOKE and RMCD signals. The first electrically switchable motor and the mirror 24 cooperate with the fourth mirror 29 and the spectrometer 30 to realize various optoelectronic tests under the low-temperature magnetic field based on the plug-in rod type superconducting magnet, including but not limited to the micro-area optoelectronic tests such as PL, Raman, SHG under the low-temperature magnetic field.

[0024] The system of the present application can effectively improve the micro-area test resolution, and the laser beam expansion optimization can make the light spot reach the diffraction limit, meeting the micro-area two-dimensional scanning requirement; the high-precision magneto-optical measurement is ensured, the stray light interference is reduced by the high-extinction-ratio component, the Kerr angle resolution of 1mdeg is realized, and the pure MOKE and RMCD signals are obtained through the polarization state modulation and signal processing cooperation, ensuring the measurement accuracy; the system also has strong function expansion, can expand the micro-area photoelectric test such as PL and Raman, and supports the software one-key switching of the optical path, and there is no light spot deviation during switching, which simplifies the operation and ensures the data reliability and consistency in different test modes.

[0025] As shown in Figure 3 The LED white light source 31 becomes parallel light after passing through the fourth achromatic lens 32, and becomes parallel light after passing through the fifth reflecting mirror 33, the fifth achromatic lens 34, the second electric switching motor and the beam splitter 35, and is focused on the back focal plane of the objective lens, and is converted into parallel light by the objective lens to uniformly illuminate the sample. The sample real space imaging passes through the low-temperature sample rod and the optical path coupling module 9, and then passes through the second electric switching motor and the beam splitter 35 and the sixth achromatic lens 36 to be focused on the CMOS camera 37. Among them, the illumination light passes through the low-temperature sample rod and the optical path coupling module 9 after passing through the beam splitter, and the low-temperature sample rod and the optical path coupling module 9 contain a relay lens, which realizes the length extension of the micro-area Kohler illumination optical path system. The imaging area of this long-distance Kohler illumination system is about 120um, and the piezoelectric module of the sample rod can quickly realize the micro-area electric sample finding under the low-temperature magnetic field.

[0026] The system of the present application optimizes the LED white light source with achromatic lenses to form parallel light to uniformly illuminate the sample, avoid imaging distortion, and provide a clear visual basis for accurate positioning. The relay lens solves the contradiction between long-distance optical path transmission and high-quality illumination, adapts to the system layout, and ensures the integrity and stability of the imaging link in extreme environments. The 120um imaging area balances the field of view and the recognition degree, and cooperates with the piezoelectric module to realize the electric sample finding under the low-temperature magnetic field, avoids the inconvenience of manual operation, and matches the 1um resolution, which saves time and protects the system stability. The electric beam splitter can be cut in when finding the sample and cut out when testing, without the need for manual intervention, preventing light path deviation, fitting the system full-automatic design, and improving the operation continuity.

[0027] As shown in Figure 4 The illumination light and the laser both enter the plug-in rod type superconducting magnet 10 through the low-temperature sample rod and the optical path coupling module 9. Among them, the second electric switching motor and the beam splitter 35 cut into the optical path when finding the target sample, realizing the simultaneous observation of the laser spot and the micro-area sample, and the second electric switching motor and the beam splitter 35 cut out of the optical path when testing, and the light spot has no deviation, ensuring the high efficiency of the sample signal collection.

[0028] The system of the present application can simultaneously observe the laser spot and the micro area sample when the beam splitter is cut in, directly confirm whether the spot covers the target area, avoid positioning deviation, adapt to the 1um micro area resolution requirement of the system, and lay a foundation for precise testing such as MOKE and RMCD; when the beam splitter is cut out, there is no shielding, and the spot does not deviate, which not only avoids stray light interference, improves signal collection efficiency, but also ensures that the test area and the positioning area are consistent, and guarantees the authenticity and continuity of the data. Meanwhile, the illumination light and the laser are uniformly introduced into the magnet through the coupling module, which can isolate external interference, adapt to the internal low-temperature strong magnetic field environment, and ensure stable transmission of the light path; the electric switching does not need manual operation, which simplifies the process, reduces the safety risk, is consistent with the full-automatic design of the system, and further improves the testing efficiency and safety.

[0029] As shown in Figure 5 The multifunctional micro area magneto-optical system based on the plug rod type superconducting magnet provided by the present application can simultaneously measure the MOKE and RMCD signals of the sample, obtain the information of the Kerr angle, the elliptical polarization degree and the coercive field after calibration, and analyze the spin-related magnetic properties of the material. The system can directly read the MOKE and RMCD values of the phase-locked amplifier, realize micro area magnetic domain scanning through the two-dimensional piezoelectric stage of the sample rod, and the spatial resolution is about 1um; for multi-domain magnetic materials, the magnetic domain scanning can be carried out under different fixed magnetic fields to study the magnetic domain dynamics.

[0030] As shown in Figure 6 In another embodiment of the present application, a step-by-step testing method for micro area magnetism and extended optoelectronic properties of magnetic materials is provided, which applies a multifunctional micro area magneto-optical system based on a plug rod type superconducting magnet, including S100: check the connection and state of the core components of the system, load the magnetic sample of the appropriate size and fix the alignment, and pre-check the microscopic imaging and detection link; S200: start the superconducting magnet refrigeration and stabilize to the target temperature, initialize the magnetic field to the required value, adjust the laser light path and start the photoelastic modulator and other detection modules to complete the calibration; S300: start the microscopic imaging mode, move the sample through the two-dimensional piezoelectric stage to select the target micro area, cut out the beam splitter after fine adjustment to ensure that the laser spot covers the target area to avoid light path interference; S400: set the MOKE and RMCD test parameters in the control software, collect signals with a standard sample with known magnetic parameters and calculate the calibration coefficient; S500: adjust the magnetic field by the set magnetic field step to synchronously collect the MOKE and RMCD signals, complete the micro area magnetic domain scanning through the two-dimensional piezoelectric stage to drive the sample under multiple fixed magnetic fields, and record the data; S600: switch the light path to the PL / Raman mode through the software, adjust the spectrometer parameters to collect the extended spectrum signals of the sample under different magnetic fields and temperatures; S700: save test data and generate results by analysis module, step by step demagnetization and close the power supply of each module of the system, take out the sample cleaning components and make a good record of equipment use.

[0031] Those skilled in the art can understand that the above description is only a preferred embodiment of the present application, and is not intended to limit the present application. Any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A multi-functional micro-zone magneto-optical system based on a plug-in rod superconducting magnet, characterized in that, The application relates to a plug-in rod type superconducting magnet (10) for providing a strong magnetic field test environment for a sample to be tested. A mechanical support module is used for bearing the plug-in rod type superconducting magnet (10), a MOKE and RMCD module (7), an ultra-long distance inverted microscopic imaging module (8) and a low-temperature sample rod and light path coupling module (9). The MOKE and RMCD module (7) is used for synchronously measuring a magneto-optical Kerr effect (MOKE) signal and a reflected magnetic circular dichroism (RMCD) signal of a sample. The ultra-long distance inverted microscopic imaging module (8) is used for sample real space imaging and positioning. The low-temperature sample rod and light path coupling module (9) has one end extending into the plug-in rod type superconducting magnet (10) to bear the sample to be tested and the other end being connected with the MOKE and RMCD module (7) and the ultra-long distance inverted microscopic imaging module (8) to form a light path connection. An electric control and software control module is electrically connected with each module to realize full-process automation of sample positioning, magnetic field adjustment, temperature control, light path switching and data acquisition and analysis, and the micro-area light path light spot does not deviate during the light path switching process. The mechanical support module comprises an adjustable rubber shock-absorbing foot cup (1), a bottom plate (2), a bottom stainless steel support column (3), a support panel (4), a stainless steel support column (5) and a breadboard (6).

2. The system of claim 1, wherein, The adjustable rubber shock-absorbing foot cup (1) is arranged at the bottom of the bottom plate (2); one end of the bottom stainless steel support column (3) is fixedly connected with the bottom plate (2) and the other end is fixedly connected with the support panel (4); one end of the stainless steel support column (5) is fixedly connected with the support panel (4) and the other end is fixedly connected with the breadboard (6). The MOKE and RMCD module (7) and the ultra-long distance inverted microscopic imaging module (8) are arranged on the breadboard (6). The MOKE and RMCD module (7) comprises a laser light source (11), a first achromatic lens (12), a first reflecting mirror (13), a second achromatic lens (14), a polarization beam splitter (15), a first 1 / 2 wave plate (16), a first Glan-Thomson prism (17), a second 1 / 2 wave plate (19), a beam splitting element (20), a third reflecting mirror (21), a photoelastic modulator (22), a chopper (23), a first electrically-driven switching motor and reflecting mirror (24), a second Glan-Thomson prism (25), a third achromatic lens (26), a balanced amplifier (27), a lock-in amplifier (28) and a spectrometer (30).

3. The system of claim 1, wherein, The first achromatic lens (12) and the second achromatic lens (14) constitute an expansion assembly, the laser light source is expanded and the divergence angle is reduced by three times, the laser light is focused to the sample to reach the diffraction limit spot size, and the spatial resolution of the micro-area two-dimensional scanning test is enhanced. The first Glan-Thomson prism (17) and the second Glan-Thomson prism (25) have a high extinction ratio of 100000:1, the interference of stray light and background noise is obviously reduced, the signal-to-noise ratio of a weak signal is improved, the system can detect a Kerr angle resolution of 1 mdeg. ​ The first Glan-Taylor prism (17) is incident at an angle of 45° to the optical axis of the photoelastic modulator (22), and modulates the light into a 50MHz sine wave, so that the linearly polarized light changes in linear-circular-linear-circular-linear polarization state in a very short period. The chopper (23) modulates the light into a 100Hz rectangular wave. The signal light is focused by the second Glan-Taylor prism (25) and the third achromatic lens (26) to the balanced amplifier (27) to convert into a voltage signal. The photoelastic modulator (22), the chopper (23) and the balanced amplifier (27) are connected with the lock-in amplifier (28). The signal of the chopper (23) is the information of light intensity change, and the signal of the photoelastic modulator (22) carries the information of light intensity and polarization change. The pure MOKE and RMCD signals can be obtained by dividing the two signals. The first electric switching motor and mirror (24) cooperates with the fourth mirror (29) and the spectrometer (30) to realize various photoelectric tests under the low-temperature magnetic field based on the plug-in superconducting magnet, including but not limited to PL, Raman, SHG and other micro-area photoelectric tests under the low-temperature magnetic field.

4. The system of claim 3, wherein, The spectrometer (30) cooperates with the first electric switching motor and mirror (24) to realize the photoluminescence (PL), Raman and second harmonic (SHG) micro-area photoelectric test of the sample to be tested.

5. The system of any one of claims 1-3, wherein, The super-long distance inverted microscopic imaging module (8) includes an LED white light source (31), a fourth achromatic lens (32), a fifth mirror (33), a fifth achromatic lens (34), a second electric switching motor and beam splitter (35), a sixth achromatic lens (36) and a CMOS camera (37). The illumination light source passes through the beam splitter, then passes through the low-temperature sample rod and optical coupling module (9) which includes a relay lens, and realizes the length extension of the micro-area Kohler illumination optical path system. The imaging area of the long-distance Kohler illumination system is about 120um, and the piezoelectric module of the sample rod can quickly realize the micro-area electric sample searching under the low-temperature magnetic field. When the target sample is the second electric switching motor and beam splitter (35), the light path is cut in, and the laser spot and the micro-area sample are observed at the same time. When testing, the second electric switching motor and beam splitter (35) are cut out of the light path and the spot does not shift, which ensures the high efficiency of sample signal collection.

6. The system of any one of claims 1-3, wherein, The low-temperature sample rod and optical coupling module (9) is internally provided with a relay lens, which is used to extend the length of the Kohler illumination system in the super-long distance inverted microscopic imaging module (8), and realizes long-distance optical path transmission.

7. The system of any one of claims 1-3, wherein, The electric control and software control unit comprises a multi-path control power supply, a variable speed handle, an XYZ axis piezoelectric scanning table, an electric switching motor, an electric rotating motor, a temperature controller and a PWM signal generator; the XYZ axis piezoelectric scanning table is arranged on the low-temperature sample rod and the light path coupling module (9) and is used for driving the sample to be measured to realize micro-area scanning; the temperature controller is used for controlling the temperature of the low-temperature sample rod and the light path coupling module (9) to realize the temperature control of the sample to be measured; and the multi-path control power supply is used for providing excitation current for the plug-in rod type superconducting magnet (10) to adjust the magnetic field strength. The software control module realizes one-key switching of the light path mode through a preset program.

8. The system of any one of claims 1-3, wherein, The maximum steady-state magnetic field strength that can be generated by the plug-in rod type superconducting magnet (10) is 16 tesla; and the temperature control range of the temperature controller in the electric control and software control unit is 1.5K-300K, so that the temperature control of the sample to be measured from low temperature to room temperature can be realized.

9. The system of any one of claims 1-3, wherein, The XYZ axis piezoelectric scanning table in the electric control and software control unit cooperates with the MOKE and RMCD module (7) to realize micron-level micro-area magnetic domain scanning of the sample to be measured, and the spatial resolution of the system is about 1μm; and the Kerr angle resolution of the system is 1mdeg, so that a weak magneto-optical signal can be detected. 10.A method for testing micro-area magnetism and extended photoelectric properties of a magnetic material, which applies the multifunctional micro-area magneto-optical system based on a plug-in rod type superconducting magnet according to any one of claims 1-9, and comprises: S100: checking the connection and state of the core components of the system, loading and fixing a magnetic sample of an appropriate size, and pre-checking the micro-imaging and detection link; S200: starting the superconducting magnet refrigeration and stabilizing to a target temperature, initializing the magnetic field to a required value, adjusting the laser light path, and starting the photoelastic modulator and other detection modules to complete calibration; S300: starting the micro-imaging mode, moving the sample through the two-dimensional piezoelectric table to select a target micro-area, fine-tuning to ensure that the laser spot covers the target area, and then cutting out a beam splitter to avoid light path interference; S400: setting the MOKE and RMCD test parameters in the control software, collecting signals from a standard sample with known magnetism parameters, and calculating calibration coefficients; S500: adjusting the magnetic field by a set step size, synchronously collecting MOKE and RMCD signals, and recording data by driving the sample through the two-dimensional piezoelectric table under multiple fixed magnetic fields to complete micro-area magnetic domain scanning; S600: switching the light path to the PL / Raman mode through the software, adjusting the spectrometer parameters, and collecting extended spectrum signals of the sample under different magnetic fields and temperatures; S700: saving the test data and generating results through an analysis module, gradually demagnetizing and turning off the power supply of each module of the system, taking out the sample, cleaning the components, and making a good record of the use of the equipment.

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