DIELECTRIC-RELATED OPTICAL LINE SHIFTS IN SRTIO3 - CR3+

Very unusual and large shifts of the R lines of Cr3+ with temperature and applied electric fields were observed. Below the tetragonal transition temperature, these shifts were found to have a behavior similar to that of the reciprocal dielectric constant of SrTiO3. The electric field shift is shown to be due to the ionic polarization induced by the electric field. The R-line thermal shift cannot be explained by the usual theory of interaction with the acoustic lattice modes. The temperature dependence of the dielectric constant and the R-line shift is discussed in terms of interaction with the low-frequency optical-phonon branch. The tetragonal transition of SrTiO3 at 107°K is instrumental in producing a discontinuity in the slope of the R-line shift versus temperature. © 1969 The American Physical Society.