Micro-MOKE with optical interference in the study of 2D Cr2Ge2Te6 nanoflake based magnetic heterostructures

Due to its high sensitivity and sub-micrometer spatial resolution, the microscopic magneto-optical Kerr effect (micro-MOKE) technique has been widely utilized in the study of two-dimensional (2D) magnetic materials and heterostructures. Here, by taking 2D Cr2Ge2Te6 nanoflakes on a silicon wafer substrate as a model system, we present the effect of optical multilayer interference induced "optical artifacts" on the effective micro-MOKE measurements in such a system. It is found that not only the magnitude but also the sign of the micro-MOKE signal could be modulated by the "optical artifacts" with the variation of either the Cr2Ge2Te6 nanoflakes' thickness or probe light wavelength. The detailed analysis based on the multilayer interference model reveals that there are two kinds of MOKE signals, sign reversal and magnitude modulation behavior, and the interference effect on the MOKE response can be easily predicted from unpolarized optical images. Our findings provide instructional principles on the promotion of micro-MOKE characterization as well as the optical studies in van der Waals magnets.