Characteristic Structural Phase Transition in Perovskite-Type Compounds

Abstract

The tetragonal rotation of Ti${\mathrm{O}}_{6}$ octahedra in SrTi${\mathrm{O}}_{3}$ and the trigonal rotation of Al${\mathrm{O}}_{6}$ octahedra in LaAl${\mathrm{O}}_{3}$ were measured by paramagnetic resonance below their respective phase transitions. The normalized rotation angles $\ensuremath{\alpha}$ vary quantitatively in the same way as a function of reduced temperature. Thus $\ensuremath{\alpha}$ is the order parameter in such transitions, which are characteristic for perovskite compounds.