Several promising non-vdW multiferroic half-metallic nanosheets ACr2S4 (A = Li, Na, K, Rb): the first-principles researches.

Half-metallic nanosheets are attracting increasing attention due to their advantages such as low power consumption, high storage density, non-volatile information in spintronics. Furthermore, the nanometer multiferroic materials exhibit new singular abundant physical capabilities and application potential. In this paper, several non-vdW multiferroic half-metallic nanosheets ACr₂S₄ (A = Li, Na, K and Rb) were predicted by the first-principles calculations. It was found that the geometric structures of these nanosheets are stable and their ground states are all ferromagnetic. The half-metallicity of these nanosheets is all stable within a certain biaxial stain range and their magnetic moments per unit always retain at 5.00 μ_B, which origin mainly from Cr-ions and partially from the S-ions. There is strong ferromagnetic coupling between Cr-ions and weak antiferromagnetic coupling between Cr-ions and S-ions. The half-metallicity of these nanosheets may be improved significantly by the biaxial tensile strain. Based on the crystal field theory, the two-center electronic structures t_2g⁶↑t_2g⁴↓e_g³↑were built, which provides direct physical insights into the origin of the half-metallicity and the magnetic moment. [ABSTRACT FROM AUTHOR]