Dynamic Jahn-Teller effect for the chromous ion in KMgF3

Abstract

The dynamic Jahn-Teller effect for the chromous ion in KMg${\mathrm{F}}_{3}$ is characterized by acoustic measurements. Acoustic-relaxation measurements and the temperature dependence of the acoustic-paramagnetic-resonance spectra are used in conjunction with theoretical vibronic levels of a molecular-cluster approximation to evaluate the tunnel splitting ($\ensuremath{\delta}=10$ ${\mathrm{cm}}^{\ensuremath{-}1}$) and spin-orbit splitting ($D=1.2$ ${\mathrm{cm}}^{\ensuremath{-}1}$). These values ($\ensuremath{\delta}, D$) are approximately one half those observed for MgO:${\mathrm{Cr}}^{2+}$ where the octahedral coordination of the chromous ion is with oxygen anions compared to fluorine anions in KMg${\mathrm{F}}_{3}$. The gyromagnetic ratio as well as the internal strains are estimated to be less in KMg${\mathrm{F}}_{3}$ than in MgO.