Abstract
The optical properties of the isoelectronic compoundsLaCoO3 and HoCoO3 have been experimentally and theoretically investigated. We have measured the real(ε1(ω)) andimaginary (ε2(ω)) parts of the dielectric function, the reflectanceR(ω) and the optical conductivity at room temperature. A shift of the mostpronounced spectral features to the high energy region by 0.3 eV associatedwith larger distortions due to the smaller rare earth ionic radii inHoCoO3 in comparisonwith LaCoO3 was observed. Also there was found an enhancement of theabsorption intensity in the range 1.3–2.3 eV in all kinds of spectra ofHoCoO3, which can be attributed on the basis of the results ofLDA +U calculations to the different spin states of theCo3+ ion in these compounds. The shift of the onset of the absorption from less than 0.1 eV inLaCoO3 to0.7 eV in HoCoO3 and an absorption intensity enhancement in a narrow spectral range 1.2–2.6 eV inHoCoO3 are clearly seen from the calculated convolution of partial densities of states obtained in theLDA +U approach. Such changes are assumed to be induced by the differentCo3+ spin states in these compounds at room temperature.
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