Strain-controllable high Curie temperature and magnetic anisotropy energy in two-dimensional Fe2Si and Fe2Ge

Effect of strain on the magnetic anisotropy (MA) and Curie temperature (Tc) of monolayer Fe2Si and Fe2Ge with out-of-plane/perpendicular MA is performed by using first-principles calculations. Based on the second-order perturbation theory of spin-orbit coupling (SOC). It is found that with the increase of tensile strain, the out-of-plane MA is enhanced. Meanwhile, the applied compressive strain further stabilized the ferromagnetic state with out-of-plane MA reserved, though partially weakened. The mechnism can be explained from the competitive effect between direct exchange interaction and superexchange interaction based on the response of bonding behavior of the neighboring atoms to the applied strain. By using Monte Carlo (MC) simulations, we found that the Tc increased from 600 K to 890 K for monolayer Fe2Si and from 380 K to 700 K for monolayer Fe2Ge under the strain ranging from 5% to −5%. Our results indicate that monolayer Fe2Si and Fe2Ge are promising candidates suitable for applications in high-density data storage with high MA and Tc.