Crystallization and magnetic properties of Fe84B9Nb7 amorphous ribbons

Abstract

The amorphous Fe84B9Nb7 and its nanocrystallization have been studied by x-ray, Mossbauer spectroscopy and magnetic moment measurements. The average hyperfine field H-hf(T) of the amorphous state shows a temperature dependence of [H-hf(T)-H-hf(0)]/H-hf(0) = -0.52(T/T-C)(3/2)-0.34(T/T-C)(5/2) for T/T-C < 0.7, indicative of spin-wave excitation. The quadrupole splitting just above the Curie temperature T-C is 0.41 mm/s, whereas the average quadrupole shift below T-C is zero. The Curie and crystallization temperatures are determined to be T-C = 330 K and T-x = 750 K, respectively, for a heating rate of 5 K/min. The occupied area of the nanocrystalline phase at the optimum annealing temperature is about 73%.