Charge and orbital ordering and spin-state transition driven by structural distortion in YBaCo2O5

Abstract

We have investigated electronic structures of antiferromagnetic YBaCo2O5 using the local spin-density approximation+U method. The charge and orbital ordered insulating ground state is correctly obtained with the strong on-site Coulomb interaction. Co2+ and Co3+ ions are found to be in the high spin and intermediate spin state, respectively. The tetragonal to orthorhombic structural transition is responsible for the ordering phenomena and the spin states of Co ions. We have found that, the contribution of the orbital moment to the total magnetic moment is substantially large in YBaCo2O5.