High-temperature background of internal friction in (Co$_{45}$Fe$_{45}$Zr$_{10}$)$_x$(Al$_2$O$_3$)$_{100-x}$, Co$_x$(CaF$_2$)$_{100-x}$, and Co$_x$(PZT)$_{100-x}$ nanocomposites

The elastic $(G)$ and inelastic $(Q^{-1})$ properties of (Co$_{45}$Fe$_{45}$Zr$_{10}$)$_x$(Al$_2$O$_3$)$_{100-x}$, Co$_x$(CaF$_2$)$_{100-x}$, and Co$_x$(PZT)$_{100-x}$ ($x$ = 23–76 at%) nanocomposites obtained by ion-beam sputtering are studied in the temperature range 300–900 K. A significant rise in the $Q^{-1}(T)$ curve is observed at temperatures above 650 K, which is attributed to thermally activated migration of point defects under the conditions of confined geometry.