The magnetic properties in two-dimensional Cr2X2Y6 (X=Ge, Si; Y=Te, Se) modulated by strain and electric field

Nowadays, electronic devices based on spin properties have rapidly developed, which played an important role in the field of efficient information storage and transmission. In this work, the geometric structures and magnetic properties of two-dimensional (2D) monolayer Cr₂X₂Y₆ (X = Ge, Si; Y=Se, Te) have been investigated systematically. Especially, a comparative study on the geometric structures, electronic structures, magnetic anisotropy and Curie temperature (T_c) of 2D Cr₂Ge₂Te₆ (CGT), Cr₂Si₂Se₆ (CSS) and Cr₂Si₂Te₆ (CST) have been studied. The magnetic ground state of monolayer CGT, CST and CSS is FM with out-of-plane magnetic anisotropy. The results show that CGT, CST and CSS are all semiconductors, and the band gaps with spin up (down) of CGT, CSS and CST are 0.21eV (0.68eV), 0.10eV (0.45eV), and 0.19eV (1.14eV), respectively. The T_c of monolayer CGT, CSS and CST are 61, 39 and 91 K based on mean field theory, which are 55, 34 and 78 K by Monte Carlo simulation. By applying biaxial strains, the band gap of monolayer CGT, CST and CSS increases firstly and then decreases under tensile strain, and the magnetic anisotropy changes greatly under compression strain. By employing vertical electric field, the results show that CST changes from semiconductor to semi-metal under the electric field of 0.8 V/Å, while CGT and CSS change little. The results provide theoretical basis for the development of novel spintronic devices and flexible electronic devices in future applications.