Charge and Spin Order in RNiO₃ (R=Nd, Y) by LSDA+U Method

Abstract

Electronic structures of NdNiO₃ and YNiO₃ are calculated by using the LSDA+U method with rotational invariance. No orbital order on Ni sites is observed in the calculations for the two systems. Different types of charge ordering are found in the two systems. In a small distorted system NdNiO₃, all nickel ions are trivalent, while oxygen sites show charge ordering and spin density polarization in the energy range of Ni e_g σ^* band. In a large distorted system YNiO₃, charge disproportionation occurs. Therefore, the charge ordering stabilizes the asymmetry of the arrangement of Ni magnetic moments in both systems.