Spin-Polarized Scanning Tunneling Microscopy of Epitaxial Fe₃GeTe₂

Van der Waals ferromagnet Fe₃GeTe₂ (FGT) has become an exciting material due to its perpendicular magnetic anisotropy and high Curie temperature that can be tuned to above room temperature. In addition, skyrmion spin textures have been observed in exfoliated FGT flakes and FGT/WTe₂ heterostructures. However, the microscopic origin of the skyrmion order remains unclear. Here, we utilize molecular beam epitaxy (MBE) for atomic layer-by-layer synthesis of monolayer and multilayer FGT films and heterostructures. Scanning tunneling microscopy (STM) is performed to characterize the atomic-scale structure and Cr tips are employed for spin-polarized STM (SPSTM) to investigate the magnetic hysteresis and domain structure. Structural analysis of the sample surface by STM attests to the high quality of films grown with MBE. SPSTM spectroscopy at different perpendicular magnetic fields reveals spin contrast originating from surface magnetism. Under optimized tunneling conditions with high spin contrast, we observe magnetic switching events as the field is swept and local magnetic hysteresis loops are obtained. We will report our latest results on FGT layer dependence and the relationship between structure and magnetism at the atomic scale.