Relaxation losses of magnetic excitations in nanoscale films of yttrium iron garnet

Relaxation losses of magnetic excitations in nanoscale films of Y$_{3}$Fe$_{5}$O$_{12}$ (YIG) were studied. The films were obtained by laser molecular-beam epitaxy (LMBE). Ferromagnetic resonance linewidth $\Delta H$ was found to increase sharply as the temperature decreased from 300 to 77 K. The observed growth of $\Delta H$ is explained by typical relaxation processes caused by the presence of Fe$^{2+}$ ions. This effect is not observed in thick films of YIG grown by liquid-phase epitaxy and containing Pb$^{4+}$ ions, and, hence, we have concluded that the presence of acceptor ions in YIG films obtained by LMBE will facilitate decreasing the concentration of Fe$^{2+}$ ions and, a result, diminishing relaxation losses.