Electronic structure of Ca3CoXO6 (X=Co, Rh, Ir) studied by x-ray photoemission spectroscopy -: art. no. 073406

We have obtained Co 2p, Rh 3d, Ir 4f, and valence-band x-ray photoemission spectra of Ca3Co2O6, Ca3CoRhO6, Ca3CoIrO6, and Sr3ZnIrO6 in order to determine the valence states of Co. The spectral features are consistent with the picture that Co is in the trivalent state at both trigonal prismatic and octahedral sites with high- and low-spin states, respectively, in Ca3Co2O6, whereas Co is in the high-spin Co2+ state for Ca3CoRhO6 and Ca3CoIrO6. This conclusion resolves a recent controversy regarding the valence and spin states of Co in Ca3Co2O6 and Ca3CoRhO6. This is the first x-ray photoemission spectroscopic study of this family of oxides.