The electronic and ir spectra of rare-earth perovskites of the general formula LnZO<sub>3</sub>, where Ln is the rare earth ion or yttrium and Z is Cr, Mn, or Fe, have been studied in detail. The results have been discussed in terms of crystallography, magnetic properties, covalency of Ln–O and Z–O bonds, and Goodenough's one electron energy diagrams. In all these compounds the rare earth ions do not markedly affect the electronic transitions of the transition metal ions; the 3<i>d</i> electrons clearly exhibit localized behavior. Both the electronic and ir spectra of the LnZO<sub>3</sub> perovskites are comparable to the spectra of the corresponding transition metal sesquioxides, Z<sub>2</sub>O<sub>3</sub>.
G. V. Subba Rao, C. N. R. Rao, and J. R. Ferraro, "Infrared and Electronic Spectra of Rare Earth Perovskites: Ortho-Chromites, -Manganites and -Ferrites," Appl. Spectrosc. 24, 436-445 (1970)