Possibility for an intermediate-spin ground state in the charge-transfer materialSrCoO3

We discuss the possibility of an intermediate-spin ground state for a ${\mathit{d}}^5$ (${\mathit{d}}^6$) system. The intermediate-spin state is stabilized by the relative stability of the ligand hole state that it hybridizes with. Using atomic multiplet calculations we showed that an intermediate-spin ground state is possible for ${\mathrm{Co}}^{4+}$ (${\mathit{d}}^5$) when the ${\mathit{d}}^6$L state dominates the ground state. From a comparison of the experimental Co 2p x-ray absorption spectroscopy spectrum with the calculated one we assume an intermediate-spin ground state for ${\mathrm{SrCoO}}_3$. The intermediate-spin ground state is a highly symmetrical state with high-spin Co ${\mathit{d}}^6$ ions on each site. Each oxygen then contributes 1/3 hole which is antiferromagnetically coupled to both neighboring Co ions. In this way the itinerant oxygen holes couple the high-spin Co ${\mathit{d}}^6$ ions ferromagnetically. With this model of oxygen holes that introduce ferromagnetic correlations we can also explain the spin-glass behavior for slightly doped ${\mathrm{LaCoO}}_3$.