Great enhancement of Curie temperature and magnetic anisotropy in two-dimensional van der Waals magnetic semiconductor heterostructures
Xue-Juan Dong, Jing‐Yang You, Zhen Zhang, Bo Gu, Gang Su
Abstract
In two-dimensional (2D) magnetic systems, large magnetic anisotropy is needed to stabilize the magnetic order according to Mermin-Wagner theorem. Based on density-functional theory (DFT) calculations, we propose that the magnetic anisotropic energy (MAE) of 2D ferromagnetic (FM) semiconductors can be strongly enhanced in van der Waals heterostructures by attaching a nonmagnetic semiconductor monolayer with large spin-orbit coupling. We studied ${\mathrm{Cr}}_{2}{\mathrm{Ge}}_{2}{\mathrm{Te}}_{6}/{\mathrm{PtSe}}_{2}$ bilayer heterostructures, where each layer has been realized in recent experiments. The DFT calculations show that the MAE of ${\mathrm{Cr}}_{2}{\mathrm{Ge}}_{2}{\mathrm{Te}}_{6}/{\mathrm{PtSe}}_{2}$ is enhanced by 70%, and the Curie temperature ${T}_{C}$ is increased far beyond room temperature. A model Hamiltonian is suggested to analyze the DFT results, showing that both the Dzyaloshinskii-Moriya interaction and single-ion anisotropy contribute to the enhancement of the MAE. Based on the superexchange picture, we find that the decreased energy difference between $3d$ orbitals of Cr and $5p$ orbitals of Te contributes partially to the increase of ${T}_{C}$. Our present work indicates a promising way to enhance the MAE and ${T}_{C}$ by constructing van der Waals semiconductor heterostructures, which will inspire further studies on the 2D magnetic semiconductor systems.