Soft-Mode Study of the Stress-Induced Phase Transitions near T in SrTiO3

We have studied the stress‐induced phase transitions of SrTiO₃ in the vicinity of $T_0$ , by means of soft‐mode Raman scattering. Theoretical expressions for the soft‐mode frequencies, critical stresses, and linear displacements of the vibrating atoms are described in terms of the phenomenological theory. Experimental results of soft‐mode frequencies versus stress in the [111] direction, for temperatures both below and above $T_0$ are given. The temperature dependence of the coefficient of the harmonic force, in the vicinity of $T_0$ is shown and discussed. Critical stresses for temperatures ${\mathrm{T\hspace{0.17em}>\hspace{0.17em}T}}_0$ are measured, and the equilibrium values of the linear displacements of the vibrating atoms are derived from the experimental results.