ultrathin films*

Transition metal chalcogenides are versatile for realizing topological phenomena. Quasi 2D Cr₂Te₃ MBE films enable control over charge/spin degrees of freedom, leveraged by strain tunability at the substrate/film interface. Cr₂Te₃ films display perpendicular magnetic anisotropy with a Curie temperature of ~ 160 K for thickness of 20 unit cells, whose structure and magnetic properties are examined by transmission electron microscopy, polarized neutron reflectometry and scanning tunneling microscopy. This is accompanied by rich magnetotransport properties: apart from the ordinary Hall effect with linear field dependence, the anomalous Hall effect manifests a unique temperature-dependent sign reversal. Novel topological Hall effect (THE) appears, related to the emergence of magnetic skyrmions, nanometer-sized quasiparticles with topological spin textures. The magnitude of the THE is tunable via interface strain that can be varied by film thickness and choice of substrate (Al₂O₃ and SrTiO₃). The effective interface-driven tunability of non-coplanar spin textures in Cr₂Te₃ ultrathin films offers new opportunities for spintronics.