First-principles prediction of a two-dimensional semiconductor ferromagnetism in Cr2X2Se6 (X = Al, Ga, In) materials

Abstract

Based on first-principles calculations, I have predicted the existence of a new class of two-dimensional (2D) transition-metal tri-chalcogenides (TMTCs) materials with the chemical formula Cr2X2Se6 (X = Al, Ga, In). The molecular dynamics and phonon dispersion calculations showed that these materials are thermally and dynamically stable, suggesting that they can be synthesized in the laboratory. Cr2X2Se6 structures are all semiconductors with an indirect bandgap, and the bandgap sizes decrease as the X atom changes from Al to Ga to In. For instance, the bandgaps of Cr2Al2Se6, Cr2Ga2Se6, and Cr2In2Se6 are 1.29, 0.91, and 0.86 eV, respectively. The Cr2X2Se6 monolayer structures exhibit ferromagnetic order and possess an out-of-plane magnetic anisotropy energy (MAE), which increases in magnitude from Al to In along the periodic table. The Curie temperature (Tc) of Cr2X2Se6 monolayers was determined using Monte Carlo simulations based on Heisenberg's model. The Tc exhibited the expected dependence on X atoms. The Cr2X2Se6 monolayers exhibit strong absorption and reflection coefficients in the visible region, with an absorption coefficient of about 105 cm−1. Overall, the discovery and development of new 2D materials with interesting electronic, magnetic, and optical properties offer many opportunities for developing new spintronic and magneto-optical devices that can be used in many different applications.