Mössbauer Effect ofEr166in Erbium Orthochromite

Abstract

The hyperfine structure of the M\"ossbauer resonance in ErCr${\mathrm{O}}_{3}$ has been studied from 4 to 40\ifmmode^\circ\else\textdegree\fi{}K. At the lowest temperature, a well-resolved hfs pattern is obtained; from this the moment of the ordered ${\mathrm{Er}}^{3+}$ ion can be determined to be $6.2{\ensuremath{\mu}}_{\ensuremath{\beta}}$. At higher temperatures, relaxation effects smear the spectrum, and the data have been analyzed using a model in which the Kramers doublet which is the lowest Stark level of ${\mathrm{Er}}^{3+}$ is split by a molecular field coming from both the Cr and Er sublattices. Above the ${T}_{N}(\mathrm{Er})$, the relaxation rate follows an Orbach process, and below ${T}_{N}$ the rate is roughly constant, with $\ensuremath{\tau}\ensuremath{\approx}2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}10}$ sec. The first excited Stark level was found to lie about 47\ifmmode^\circ\else\textdegree\fi{}K above the ground Kramers doublet.