Electron Paramagnetic Resonance Investigation of Successive Phase Transitions in KCdF₃

Abstract

An EPR investigation of Cr³⁺-nearest neighbour Cd²⁺ vacancy center in KCdF₃ has been made over a temperature range 290–490 K. The temperature dependence of the spectrum in the [100] field direction evidently shows the presence of the successive phase transitions at 485 and 471 K, From the field direction dependence for the magnetic field in the (011) and (001) planes, it was found that the induced X-mode is not condenced significantly in the third phase below 471 K and so the first and second phase transitions can be explained by the condensation of the M₃ and R₂₅^x+R₂₅^y soft phonon modes at the [110] and [111] zone boundary in the cubic Brillouin zone, respectively.