Spin‐Waves in Amorphous FexGe1−xThin Films

Magnetic properties of ${\mathrm{Fe}}_{\mathrm{x}}{\mathrm{Ge}}_{\text{1−}\mathrm{x}}$ amorphous thin films were studied by F.M.R. between 4.2 and 300° K for $\text{0.5\hspace{0.17em}<\hspace{0.17em}}\mathrm{x}\text{\hspace{0.17em}<\hspace{0.17em}0.65}$ . From the resonance spectra, the saturation magnetization, g factor, the spin‐wave stiffness constant D and their temperature dependences could be determined. For $\mathrm{x}\text{\hspace{0.17em}>\hspace{0.17em}0.6\hspace{0.17em}}{\mathrm{M}}_{\mathrm{s}}(\mathrm{T})$ follows the Bloch law and D(T) a ${\mathrm{T}}^{\alpha }$ law where $\text{3/2\hspace{0.17em}⩽\hspace{0.17em}α\hspace{0.17em}⩽\hspace{0.17em}2}$ . Near 0°K D(0) deduced from magnetization measurements and from S.S.W. spectra are in good agreement. For $\mathrm{x}\text{\hspace{0.17em}<\hspace{0.17em}0.6}$ and with decreasing Fe content the S.S.W. spectra progressively disappears and M_s (T) deviates largely from the Bloch law.