Infrared and Raman Spectra and Lattice Vibrations of Some Oxide Spinels

The infrared transmission and reflection spectra of Co II Co III 2 O 4 , CoAl 2 O 4 , ZnFe 2 O 4 and MnFe 2 O 4 and the single crystal Raman spectra of Co II Co III 2 O 4 and CoAl 2 O 4 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 II Co III 2 O 4 , CoAl 2 O 4 and ZnFe 2 O 4 , 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.