Strain Tunable Electronic Band Structure and Magnetic Anisotropy of CrI3 Bilayer

Abstract

Bilayer (BL) CrI3 attracts major attention among two dimensional (2D) materials due to the exhibition of unique interlayer antiferromagnetic ordering in contrast to other atomically thin films exhibiting long-range ferromagnetic ordering. It is believed that the high temperature monoclinic AB′ stacking plays the key role to induce unusual antiferromagnetic interlayer coupling in BL CrI3. The magnetic states of this system can be effectively controlled by external perturbations like magnetic field, electric field, carrier doping, strain etc. So, it is expected that strain effects can show a distinct behavior in the magnetic transition in BL CrI3. Here, we have studied the electronic and magnetic properties of BL CrI3 under in-plane biaxial and out-of-plane vertical strain from compression to stretch through density functional theory calculations. A compressive biaxial strain around −2.5 can induce a transition from AFM to FM magnetic ground state which continues upto −6 strain. Beyond this point, a second transition from FM to AFM1 state occurs. Detailed analysis of electronic structure indicates a strain induced direct to indirect band gap transition. Magnetic anisotropy energy (MAE) calculations show an out-of-plane easy axis for pristine CrI3 BL and this feature remains unchanged in the entire range of applied strain. It is also found that most of the perpendicular magnetic anisotropy contribution comes from the iodine atoms. Large MAE found in BL CrI3 may find useful applications in high density data storage devices.