Electron Paramagnetic Resonance Investigation of Phase Transition in RbCdF3

An EPR investigation of Cr 3+ center associated nearest-neighbor Cd 2+ vacancy in RbCdF 3 has been carried out in the temperature range from 300 to 77 K. The field-direction derendence of the spectrum in the (001) plane at 77 K evidently shows the alternate rotations of the fluorine octahedra around the tetragonal c -axis. This behavior should originate from the distortion of nearest-neighbor fluorine ion caused by Cd 2+ vacancy. The results indicate that this center is a sensitive probe to detect the rotations of octahedra caused by the phase transition for multidomain sample and is capable of determining the crystal structure in the low symmetry phase conclusively.