Dimension-dependent magnetic anisotropy for tunable anomalous Hall effect in transition metal dichalcogenides

Abstract

Two-dimensional (2D) ferromagnetism at room temperature is highly desired in spintronic devices and applications. Recently, ${\mathrm{CrTe}}_{2}$ film has been successfully synthesized. Bulk ${\mathrm{CrTe}}_{2}$ has in-plane magnetic anisotropy (MA), and the Curie temperature reaches up to 300 K. When the dimensions are down to two, MA switches to out-of-plane. However, the mechanism of MA transition from in-plane to out-of-plane remains unknown. Here, we investigate the switching of MA in ${\mathrm{CrTe}}_{2}$ by second-order perturbation theory. The MA energy (MAE) originates from competition between ${p}_{z}/{p}_{y}$ and ${p}_{x}/{p}_{y}$ orbital hybridization, which contributes to out-of-plane and in-plane MA, respectively. The ${p}_{x}/{p}_{y}$ orbital hybridization, induced by van der Waals force, is absent in the monolayer. Moreover, the out-of-plane MA of monolayer ${\mathrm{CrTe}}_{2}$ breaks mirror symmetry, producing an anomalous Hall effect. Slight charge doping is significant to achieve a tunable anomalous Hall effect. Based on charge doping, we design a spintronic anomalous Hall device by taking advantage of the easily controllable properties of ${\mathrm{CrTe}}_{2}$. This highly thickness-dependent magnetism provides a perspective to control the magnetic properties of 2D materials.