Low-Temperature Ferromagnetic Relaxation in Yttrium Iron Garnet

Abstract

The ferromagnetic spin lattice relaxation time, ${\ensuremath{\tau}}_{0}$, has been obtained from 4.2\ifmmode^\circ\else\textdegree\fi{} to 300\ifmmode^\circ\else\textdegree\fi{} K in single-crystal yttrium iron garnet in which considerable care was taken to reduce both the extraneous rare earth and ferrous impurity ions. The measurements are shown to be indicative of the purely ferric ion lattice at temperatures considerably lower than we previously had been able to attain. A new feature brought out in these data is the observation that below approximately 150\ifmmode^\circ\else\textdegree\fi{}K, ${{\ensuremath{\tau}}_{0}}^{\ensuremath{-}1}$ vs $T$ is steeper than proportional to $T$, which implies an extremely low value at 4.2\ifmmode^\circ\else\textdegree\fi{}K. As a result of this, the nature of the ferric ion relaxation is more clearly defined over the low-temperature region.