The Magneto-optical Kerr Spectroscopy Study Of Quasi-two-dimensional Magnetic Material

Two-dimensional magnetic materials combine two-dimensional and magnetic properties,which are expected to provide an effective way to construct future photoelectron spin devices,and have become an important research direction in the field of condensed matter physics.In a two-dimensional magnetic material system,the topologically protected magnetic structure and huge anisotropy make the material's response to external fields(magnetic field,light field,etc.)different from traditional magnetic materials.The manifestation,physical origin,and the stability and relaxation process of its magnetic structure under external field disturbances may contain new physical connotations.The observation and analysis of these phenomena can help people deeply understand the generation mechanism and regulation characteristics of low-dimensional magnetic materials,and provide a basis for finding more new topological magnetic structures and the development of new spin optoelectronic devices based on two-dimensional magnetic materials in the future.In order to carry out research in this area,a combination of static magnetism and dynamic magnetism can be used to fully reveal the magnetic properties of two-dimensional magnetic materials on different time scales.Optical means(such as microscopy/ultrafast magneto-optical Kerr technology)can provide high spatial/temporal resolution and detection sensitivity,and can detect the magnetic properties of nanometer-scale thin samples with micron-level spatial resolution and sub-picosecond time resolution.The characteristics have been widely used in the high-precision characterization of two-dimensional magnetic materials,so it can be used to explore the static and dynamic magnetic properties of two-dimensional magnetism under different magnetic fields and temperatures.This paper mainly carries out the following three aspects:(1)Use the magneto-optical Kerr effect,Kohler illumination principle and 4F lens group principle to design the optical path and build two sets of magneto-optical Kerr systems,namely the low-field micro-magneto-optical Kerr system and the high-field micro-magneto-optical Kerr system with 5 T,using the Nd Fe B,Dy Mn Sn,Fe₃Ge Te₂and WSe₂ samples to test whether the magneto-optical Kerr system has the capabilities of microscopic observe magnetic domain,measurement of magneto-optical Kerr and photoluminescence spectra.This is provide a powerful tool that the next step to study the quasi-two-dimensional magnetic materials.(2)Research on the magnetic domain observation and control of Cr₅Te₈ quasi-two-dimensional magnetic material on the low-field micro-magneto-optical Kerr system.A low-field microscopy magneto-optical Kerr system was used to observe the magnetic domains of Cr₅Te₈ quasi-two-dimensional magnetic materials.In this system,800 nm laser was introduced to irradiate and excite the Cr₅Te₈crystal sample in the saturated magnetization state.It was observed that the laser power density of 2.55×10⁸ m W/cm²could melt the magnetic domain.For the magnetic domain in the non-saturated state,the laser after irradiation,the shape and the magnetization characteristics of the irradiated area are changed,which realizes the laser quenching of the magnetic domain,proves that laser irradiation is an effective method to realize the local control of the magnetic domain.