Designing a ferrimagnetic-ferroelastic multiferroic semiconductor in FeMoClO 4 nanosheets via element substitution.

Exploring two-dimensional multiferroic semiconductors, combined with ferro-/ferrimagnetism and ferroelasticity as well as large spin polarization around the valence band maximum (VBM) and conduction band minimum (CBM), is highly desirable but remains a challenging task. Here, first-principles calculations, we predict such a material based on the square phase FeMoClO nanosheet, which is experimentally accessible by exfoliating its layered bulk. Pristine FeMoClO nanosheets are a weak antiferromagnet with zero spin polarization. After substituting nonmagnetic Mo with magnetic Mn, the resulting FeMnClO nanosheet becomes ferrimagnetic with magnetic ordering temperature significantly enhanced from 14 to 127 K. Besides, the FeMnClO nanosheet is a half semiconductor with its VBM and CBM 100% spin-polarized in the same spin direction. Interestingly, the initial square lattice is distorted into a rectangular one, inducing an in-plane ferroelasticity in the FeMnClO nanosheet with a switching barrier of 27 meV per atom. Moreover, under ferroelastic transition, the orientation of the magnetic easy axis can be reversibly rotated by 90°, indicating a strong magnetoelastic coupling.