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Abstract:
We have carried out a comparative theoretical study of the electronic structure of the one-dimensional Ca3CoRhO6 and Ca3FeRhO6 systems. The insulating antiferromagnetic state for Ca3FeRhO6 can be well explained by band structure calculations with the closed-shell high-spin d(5) (Fe3+) and low-spin t(2g)(6) (Rh3+) configurations. We found for Ca3CoRhO6 that Co has a strong tendency to be d(7) (Co2+) rather than d(6) (Co3+) and that there is an orbital degeneracy in the local Co electronic structure. We argue that it is the spin-orbit coupling which will lift this degeneracy thereby enabling local spin density approximation+Hubbard U band structure calculations to generate the band gap. We predict that the orbital contribution to the magnetic moment in Ca3CoRhO6 is substantial, i.e., significantly larger than 1 mu(B)/f.u.. Moreover, we propose a model to explain the contrasting intrachain magnetism in both materials.
