Comparative study of the effects of Si and Ge on the magnetic and permeability properties of FeCoNiBM (M = Si, Ge) amorphous ribbons

Abstract

In this paper, Fe₂₅Co₂₅Ni₂₅(B_0.7M_0.3)₂₅ amorphous alloys (where M=Si, Ge) were produced as ribbons by melt spinning rapidly cooled from the liquid state. Here, we report on the study of the effect of Ge and Si on the magnetic properties of these materials using vibrating sample magnetometry, broad-band (f = 100 MHz to 18 GHz) ferromagnetic resonance (FMR) with a coplanar waveguide-based spectrometer, and frequency dependence of permeability measurements. The saturation magnetization of ribbons containing Ge is lower by about 35 % than those containing Si. However, in the Fe₂₅Co₂₅Ni₂₅(B_0.7Si_0.3)₂₅ sample, the coercive field increased compared to the alloy with Ge, which can be attributed to internal stresses. FMR experiments showed that the resonance field increases with the frequency of microwave radiation, following Kittel's equation. The slope extracted from linewidth as a linear function of frequency for Fe₂₅Co₂₅Ni₂₅(B_0.7Si_0.3)₂₅ and Fe₂₅Co₂₅Ni₂₅(B_0.7Ge_0.3)₂₅, corresponding to a nominal Landau-Lifshitz-Gilbert phenomenological damping parameter, with values of $\alpha$ = 0.002 and 0.0015, respectively. The real and imaginary parts of the complex permeability were measured in the frequency range of 5–13 MHz. The ribbon samples demonstrated considerable values for frequency-dependent applications, with appreciable initial permeabilities over 3500 and 5000 for Fe₂₅Co₂₅Ni₂₅(B_0.7Si_0.3)₂₅ and Fe₂₅Co₂₅Ni₂₅(B_0.7Ge_0.3)₂₅, respectively.