[en] Relaxation losses of magnetic excitations in nanoscale films of Y₃Fe₅O₁₂ (YIG) were studied. The films were obtained by laser molecular-beam epitaxy (LMBE). Ferromagnetic resonance linewidth ΔH was found to increase sharply as the temperature decreased from 300 to 77 K. The observed growth of ΔH is explained by typical relaxation processes caused by the presence of Fe²⁺ ions. This effect is not observed in thick films of YIG grown by liquid-phase epitaxy and containing Pb⁴⁺ ions, and, hence, we have concluded that the presence of acceptor ions in YIG films obtained by LMBE will facilitate decreasing the concentration of Fe²⁺ ions and, a result, diminishing relaxation losses.