Enhanced ferromagnetism in monolayer Cr2Te3 via topological insulator coupling

Exchange-coupled interfaces are pivotal in exploiting two-dimensional (2D) ferromagnetism. Due to the extraordinary correlations among charge, spin, orbital and lattice degrees of freedom, layered magnetic transition metal chalcogenides (TMCs) bode well for exotic topological phenomena. Here we report the realization of wafer-scale Cr2Te3 down to monolayer (ML) on insulating SrTiO3(111) and/or Al2O3(001) substrates using molecular beam epitaxy. Robust ferromagnetism persists in the 2D limit. In particular, the Curie temperature TC of 2 ML Cr2Te3 increases from 100 K to ∼120 K when proximitized to topological insulator (TI) (Bi,Sb)2Te3, with substantially boosted magnetization as observed via polarized neutron reflectometry. Our experiments and theory strongly indicate that the Bloembergen–Rowland interaction is likely universal underlying TC enhancement in TI-coupled magnetic heterostructures. The topological-surface-enhanced magnetism in 2D TMC enables further exchange coupling physics and quantum hybrid studies, including paving the way to realize interface-modulated topological electronics.