Magnetic and optical properties in the 1D TM-O chain compounds Sr₂TMO₃ (TM = Ni, Co): A first-principle investigation

In this paper, we have calculated the structural, electronic, magnetic and optical properties of Sr₂NiO₃ and Sr₂CoO₃ using density functional theory (DFT) within generalized gradient approximation (GGA). The crystal structure of both materials is well described with Immm (No. 71) symmetry which are isostructural with Sr₂CuO₃ and both are quasi-one-dimensional (1D) rectangular lattice G-type antiferromagnets, in consistent with the experimental data. Due to a distortion, Sr₂CoO₃ lifts the near-degeneracy dxz and dyz states of the local Co electronic configuration, which demonstrates a strong coupling between the structural lattice and the electronic configuration. The calculated band structure shows a band gap of 1.376 eV for Sr₂NiO₃ and a band gap of 1.735 eV for Sr₂CoO₃. Ni and Co ions are in the high-spin S = 1 and S = 3/2 configurations with the magnetic moments of 1.585 μB and 2.587 μB, respectively. Based on the Heisenberg Hamiltonian model, we conclude that the superexchange intrachain TM-O-TM superexchange interaction is predominant and interaction between the 1D chains is weak. According to the calculated dielectric function, absorption spectrum and electron energy loss spectrum, the optical responses suggest that Sr₂NiO₃ shows the unique anisotropic structure and interaction of the application in optoelectronics.