Electronic structure and evolution of spin state in YCoO3

Electronic structure and the evolution of the spin state of Co with temperature increase in YCoO3 have been investigated by using the ab initio density-functional calculations with local spin density approximation (LSDA) and LSDA+U methods. It is shown that the orthorhombic YCoO3 exhibits nonmagnetic ground state with Co ions in a low-spin state. Theoretical calculations predict the insulating ground state with a band gap of 1.84 eV due to the strong interactions with U=6.0 eV. The size of the band gap may be significantly influenced by the choice of the value of U. With temperature variation, simulation has been carried out by corresponding change of the lattice parameters based on the experimental data. The results suggest that YCoO3 has nonmagnetic (spin S=0) insulator nature in the low temperature range and semiconductor nature with an electronic transition of Co3+ ion from low-spin state to high-spin state in the high temperature range (600–1000 K).