Research On Method For Measuring Surface Magnetic Properties Of Materials Based On Magneto-optic Kerr Effect

Nowadays,with the widespread application of magnetic materials,precise measurement of the magnetic parameters of magnetic materials can greatly assist us in selecting suitable magnetic materials.Magneto optical Kerr effect is a new method that utilizes the polarization characteristics of incident light to detect the magnetic properties of magnetic materials.The use of magneto-optical Kerr effect detection technology has advantages such as high accuracy,fast response,and non-destructive testing,making it a new type of high-precision and high sensitivity detection technology.Based on the previous work,this paper intends to use the magneto-optical Kerr effect detection technology to measure the magneto-optical Kerr rotation angle,so as to obtain the magnetic parameters such as hysteresis loop and saturation magnetization.Firstly,based on the basic theory of magneto-optical Kerr effect,through theoretical calculation,it is obtained that the magneto-optical Kerr rotation angle is in direct proportion to the magnetization of magnetic materials,and the calculation formula of magneto-optical Kerr rotation angle is given.Starting from the principle of electromagnetic coil magnetic field and based on electrical pure iron,a magnetic field capable of generating a maximum of approximately 350 m T is designed,powered by a DC power supply of 1-10 A.Using optical components such as polarizers,Semiconductor laser with a wavelength of 650 nm,aperture apertures,and photodetectors,corresponding optical paths are designed,and experimental measurement plans are provided.On this basis,the designed magnetic field module was simulated using COMSOL software and validated.Secondly,an optical chopper and a digital phase-locked amplifier are introduced,and the optimal parameters of the digital phase-locked amplifier are determined,such as a sampling frequency of 100 k Hz for the digital phase-locked amplifier and 512 orders for the low-pass filter.Using the modulation disk of an optical chopper to convert a continuous laser into a pulsed laser,the signal detected by the photodetector is changed from a DC signal to an AC signal.The signal generated after modulation by an optical chopper serves as the reference signal for the phase-locked amplifier and undergoes phase sensitive detection with the signal to be tested.After passing through a low-pass filter,the high-frequency part is filtered out and the signal to be tested is restored.The introduction of digital phase-locked amplifiers greatly improves the accuracy of the signal to be measured.Finally,the optical system,magnetic field generation system and signal processing system are connected to form a complete magneto-optical Kerr effect detection system.The magnetization of permalloy films is measured and its hysteresis loop is drawn.The magnetization of permalloy is 313 m T,and the error is 1.7%.