T32dependence of hyperfine field and spin-wave excitations in ferromagnetic metallic glasses

The hyperfine field measured at the Fe sites of a number of glassy ferromagnets (${\mathrm{Fe}}_{75}$ ${\mathrm{P}}_{15}$ ${\mathrm{C}}_{10}$, ${\mathrm{Fe}}_{40}$ ${\mathrm{Ni}}_{40}$ ${\mathrm{P}}_{14}$ ${\mathrm{B}}_6$, ${\mathrm{Fe}}_{80}$ ${\mathrm{B}}_{20}$, ${\mathrm{Fe}}_{29}$ ${\mathrm{Ni}}_{49}$ ${\mathrm{P}}_{14}$ ${\mathrm{B}}_6$ ${\mathrm{Si}}_2$, and ${\mathrm{Fe}}_{80}$ ${\mathrm{P}}_{16}$ ${\mathrm{B}}_1$ ${\mathrm{C}}_3$) exhibits a temperature dependence of $H_{\mathrm{eff}}\mathrm{}\left(T\right)=H_{\mathrm{eff}}\mathrm{}\left(0\right)(1-B{T}^{\frac{3}{2}}-C{T}^{\frac{5}{2}}\cdots )$, indicative of spin-wave excitations in noncrystalline ferromagnets. The values of $B$ are consistently several times larger than those of crystalline ferromagnets, whereas the values of $C$ are comparable to those of crystalline cases. Consequently, the $T^{\frac{3}{2}}$ dependence dominates in an exceptionally large temperature range; up to 0.6 $T_C$. The ratio of $\frac{C}{B}$ for glassy ferromagnets is smaller, thus suggesting that the exchange interaction is of shorter range in noncrystalline ferromagnets than in crystalline ferromagnets.