Temperature dependence of the magnetization in amorphous alloys

We have used ferromagnetic resonance to measure the temperature dependence of the saturation magnetization in three glassy alloys: I: Fe29Ni49P14B6Si2 (Metglas 2826B), II: (Fe0.4Ni0,6)75P16B6Al3, and III: (Fe0.5Ni0.5)75P16B6Al3. In I we find that, for 4 ?T?300 K, the magnetization follows the relaxation M(T) =M0(1–BT3/2 −CT5/2) with B and C values fairly close to those obtained using Mössbauer and vibrating sample magnetometer techniques. For II and III it is necessary to include the effects of spin wave energy renormalization, with temperature, to account for the variation of M over a comparable temperature regime. That is, the parameter B obeys the relation: B(T) =B0[1/(1−αT5/2)]3/2. In terms of the spin wave stiffness this implies D=D0[1−β (T/Tc)5/2] meV-Å2 where, again, the parameter values are in the range found for similar systems by neutron scattering.