Mossbauer study of the SrTiO₃: Co⁵⁷ system

Abstract

The mossbauer investigation of the SrTiO³:Co⁵⁷ system has indicated the coexistence of low-spin (dε⁵) and high-spin (dε³dγ ²) ferric states, in contrast to the EPR studies which have shown that iron enters the SrTiO₃ lattice at the Ti⁴⁺ site in its high-spin trivalent (dε³dγ²) state. The relative intensities of the low-spin high-spin ferric states could be altered by thermal treatment. In highly reduced samples, high-spin ferric (dε³dγ²) and high-spin ferrous (dε⁴dγ²) states have been observed with an associated charge-compensating oxygen vacancy. The cubic-tetragonal phase transition at 110°K, caused by the accidental degeneracy of longitudinal acoustic and transverse optical modes, has been detected through the temperature variation of isomer shift of the high-spin ferric state.