Multiple structure and symmetry types in narrow temperature and magnetic field ranges in two-dimensional Cr2Ge2Te6 crystal

Multiple structure and symmetry types and their transformations are discovered in quasi-two-dimensional (quasi-2D) Cr2Ge2Te6 crystal in surprisingly very narrow temperature range of 2 K and magnetic field range of 0.07 T using a homebuilt magnetic force microscope (MFM). A series of basic domain patterns are extracted from the MFM images. Some of them seem unique to 2-D materials as they are not observed in 3-D materials, such as self-fitting disks, and fine ladder structure within Y-connected walls. Based on these findings, a phase map is drawn for the magnetic phase structures. The symmetry of the patterns are discussed. The results are not only important in developing new theories but also highly desirable in applications.