Lattice Dynamics and Phase Transitions of Strontium Titanate

摘要: The crystal dynamics of strontium titanate has been studied both experimentally and theoretically. frequency versus wave-vector dispersion curves for some the normal modes propagating along [0,0,1] direction have measured by neutron spectrometry at 90 296\ifmmode^\circ\else\textdegree\fi{}K. experiments were performed Chalk River Laboratories Atomic Energy Canada Ltd., using a triple-axis spectrometer. temperature dependence transverse optic mode lowest found to be in agreement with dielectric constant, as predicted Cochran. experimental results used obtain parameters several models, more than one which gives reasonable results. It is suggested that anomalous behavior elastic properties phase transition 110\ifmmode^\circ\else\textdegree\fi{}K are associated an accidental degeneracy two branches curves; longitudinal acoustic branch frequency. origin this relevance lattice transitions other perovskites discussed.