Anomalous Behavior of the Anisotropy and Linewidth due to Pr in Iron Garnets

Abstract

The contribution of ${\mathrm{Pr}}^{3+}$ in iron garnets to the first-order anisotropy constant and to the microwave loss is highly nonlinear with respect to the ${\mathrm{Pr}}^{3+}$ concentration and is shown to be strongly dependent on the lattice constant. The value of the anisotropy constant per Pr ion goes from -18\ifmmode\times\else\texttimes\fi{}${10}^{4}$ to about +3\ifmmode\times\else\texttimes\fi{}${10}^{4}$ erg/${\mathrm{cm}}^{3}$ as the lattice constant increases from 12.4 to 12.7 \AA{}. The microwave linewidth of ${\mathrm{Pr}}_{3}$Sc${\mathrm{Fe}}_{4}$${\mathrm{O}}_{12}$ is 21 times narrower than expected from the extrapolation of the low-concentration data of ${\mathrm{Pr}}^{3+}$ in yttrium iron garnet.