Influence of the fabrication conditions on the high frequency magnetic response of melt spun Fe_73.5Si_13.5B₉Nb₃Cu₁

Abstract
The aim of this work is to analyze the influence of the fabrication conditions on the magnetic properties of Fe_73.5Si_13.5B₉Nb₃Cu₁ melt-spun nanocrystalline ribbons. Different initial structures, amorphous and partially crystalline, have been obtained during the rapid solidification procedure. The structural characterization shows that a decrease in the quenching rate through a reduction in the tangential wheel velocity, gives rise to a partially crystalline state, characterized by the appearance of a textured α-FeSi nanocrystalline phase. The occurrence of the crystalline fraction in the initial as-cast state gives rise to a magnetic hardening with respect to the amorphous sample casted at higher quenching rate. However, the evolution of coercivity under thermal treatments is roughly independent of the initial structure. Moreover, a detailed analysis of the ac susceptibility as a function of annealing temperature shows that the ribbon obtained at lower quenching rate presents higher susceptibility values in the optimum magnetic state (T_a = 550°C, 1 h) in a wide range of driving frequency (up to 100 kHz).