Electronic structure of the delafossite-type CuMO2 (M = Sc, Cr, Mn, Fe, and Co): Optical absorption measurements and first-principles calculations

We compared the results of first-principles calculations with measured absorption spectra in thin films of delafossite-type CuMO2 (M = Sc, Cr, Mn, Fe, and Co) taken at 10 K. Two optical transitions were found: one is associated with Cu3d + O2p -> Cu3d(z2) + 4s observed in all of the CuMO2 films, and the other is associated with Cu3d + O2p -> M3d detected for M = Mn, Fe, and Co. The energy of the former transition showed an unexpected dependence on the atomic number of M. An abrupt change of this energy occurs for M = Cr, which is explained as a result of the interaction between the Cu3d(z2) + 4s and M3d bands.