Infrared and Raman Spectra and Lattice Vibrations of Some Oxide Spinels

Abstract

The infrared transmission and reflection spectra of Co^IICo₂^IIIO₄, CoAl₂O₄, ZnFe₂O₄ and MnFe₂O₄ and the single crystal Raman spectra of Co^IICo₂^IIIO₄ and CoAl₂O₄ have been measured. The frequencies of the transverse (TO) and longitudinal (LO) modes of the infrared active species have been obtained from the observed reflectivities. The TO–LO splitting supplies a criterion for the ionic character. The lattice dynamical analysis of the optically active vibrations has been made for Co^IICo₂^IIIO₄, CoAl₂O₄ and ZnFe₂O₄, in which the rigid ion model for the long-range Coulomb potential and the central force field for the short-range potential have been used. The obtained short-range potential constants have been discussed, in relation to the bond character.