Electronic and magnetic properties of a quasi-one-dimensional spin chain system Sr₃NiRhO₆

Abstract

We investigate the electronic structure of Sr₃NiRhO₆, a quasi-one-dimensional spin chain system using ab initio band-structure calculations. Spin polarized calculations within generalized gradient approximation (GGA) reveal that Ni and Rh have finite moments, and they are antiferromagnetically coupled along the chain axis in the ground state. While these results that are obtained within the local spin-density approximations provide remarkable representation of the magnetic phase, the experimentally observed insulating behavior could not be captured within this method. GGA+U calculations show that the opening up of an insulating gap requires on-site Coulomb interaction strength among the Rh 4d electrons, U_dd^Rh≈ 2.5 eV, and the correlation strength among Ni 3d electrons, U_dd^Ni≈4.5 eV, suggesting this system to be a Mott insulator. Electron correlation among d electrons leads to significant enhancement of the O 2p character of the energy bands in the vicinity of the Fermi level and the d bands appear at lower energies. Energy gap in the up-spin density of states appears to be significantly small (~ 0.12 eV) while it is >2 eV in the down-spin density of states, suggesting a possibility of spin-polarized conduction in the semiconducting phase.