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.

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In recent years two-dimensional (2D) materials with intrinsic magnetism have drawn intense research interest due to their potential application in spintronic devices. Among them, chromium trihalide family has received much attention due to the exhibition of wide range of electronic and magnetic properties. Aiming to improve their spintronic properties, we have investigated the electronic and magnetic properties of monolayer (ML) Mo-doped CrX3 (X = Cl, Br and I) using density functional theory (DFT) + Hubbard U approach. Our results show that substitution of Mo atom at the Cr site is energetically favorable. Magnetic ground state of all the members is found to be ferromagnetic which undergoes a transition to antiferromagnetic state by applying both the compressive as well as the tensile strain. All the members of ML CrX3 show magneto-crystalline anisotropy energy favoring an out-of-plane easy axis of magnetization. Our calculations further reveal that all three compounds exhibit semiconducting properties with reduced band gap compared to the ML CrX3 family. This property can make them useful in spintronic applications

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