Origin of itinerant ferromagnetism in two-dimensional Fe3GeTe2

Magnetic order in two-dimensional systems was not supposed to exist at finite temperature.In recent years,the successful preparation of two-dimensional ferromagnetic materials such as CrI,CrGeTe,and FeGeTeopens up a new chapter in the remarkable field of two-dimensional materials.Here,we report on a theoretical analysis of the stability of ferromagnetism in FeGeTe.We uncover the mechanism of holding long-range magnetic order and propose a model to estimate the Curie temperature of FeGeTe.Our results reveal the essential role of magnetic anisotropy in maintaining the magnetic order of two-dimensional systems.The theoretical method used here can be generalized to future research of other magnetic two-dimensional systems.