Temperature Dependence of Microwave Acoustic Losses in Yttrium Iron Garnet

The temperature dependence of the acoustic losses in single crystal yttrium iron garnet has been obtained at 500 and 1000 Mc/sec. The method of measurement involves propagation of plane shear waves in a cylindrical rod, the direction of propagation being along a [100] crystallographic direction. At both frequencies acoustic $Q\text{'}\mathrm{s}$ of 2×${10}^5$ have been obtained and these values are relatively insensitive to temperature for $T>\mathrm{}100\mathrm{}°$K. Below 100°K, the acoustic losses are dominated by an internal friction, $Q^{-1\mathrm{}}\mathrm{}\left(T\right)\mathrm{}$, peak near 15°K.