Surface-vacancy-induced metallicity and layer-dependent magnetic anisotropy energy in Cr2Ge2Te6

Abstract

Two-dimensional van der Waals materials have attracted considerable attention because of their promising applications in spintronic devices. This paper reports on first-principles calculations of the electronic structure and ferromagnetism of Cr2Ge2Te6 with surface Ge vacancies. These vacancies are found to remove the bandgap and induce metallicity in Cr2Ge2Te6 that persists with decreasing Ge-vacancy concentration. Meanwhile, the Ge vacancies cause an unexpected sharp increase in the magnetic anisotropy energy compared to that of perfect Cr2Ge2Te6. More importantly, how thickness affects the magnetic anisotropy energy is studied to show that the latter oscillates upon increasing the number of layers, thereby switching between the out-of-plane and in-plane magnetization directions. The present findings regarding a surface-vacancy-tuned bandgap and magnetism controlled by the layer thickness in a two-dimensional van der Waals magnet could lead to potential applications in next-generation magnetic memory storage, sensors, and spintronics.