Characteristic structural phase transition in perovskite-type compounds

The tetragonal rotation of TiO6 octahedra in SrTiO3 and the trigonal rotation of AlO6 octahedra in LaAlO3 were measured by paramagnetic resonance below their respective phase transitions. The normalized rotation angles α vary quantitatively in the same way as a function of reduced temperature. Thus α is the order parameter in such transitions, which are characteristic for perovskite compounds. © 1968 The American Physical Society.