Optoelectronic structure and magnetic properties of the low-dimensional antiferromagnetic halide Cs_2CoX4 (X = Cl, Br, I): A first-principles study

This work aims to investigate the structural, magnetic, electronic and optical properties of the low-dimensional antiferromagnets Cs_2CoX4 (X = Cl, Br, I) using density functional theory (DFT). These materials are scientifically intriguing due to the existence of multiple quantum interactions such as quantum entangled states, correlation and spin-orbit coupling (SOC). The optimization and exchange coupling parameter confirm that the materials are stable in antiferromagnetic (AFM) phase, which is consistent with the experiments. The difference in bond lengths and bond angles of the same halogen in the tetrahedral complex bonded to the cobalt ion confirms the existence of Jahn-Teller distortion. The computed band gaps are 4.34, 3.70, and 3.50 eV, respectively, and show a direct band gap nature. The magnetic anisotropic character and binding energy make these materials suitable for spintronic applications. Cs layer acts as a spacer that confines the tetrahedral layer and has a negligible contribution in the formation of bands. Various optical properties like dielectric constant, refractive index and energy loss function are calculated for these materials along different crystal axes.