Structural and magnetic studies of the nanocrystalline Nd-Fe-B-Nb alloy ribbons

¹ Institute of Physics, Częstochowa University of Technology, Al. Armii Krajowej 19, 42-200 Częstochowa, Poland
² Department of Materials Engineering, Warsaw University of Technology, ul. Wołoska 141, 02-507 Warszawa, Poland

Abstract

A detailed studies of the phase constitution, microstructure and magnetic properties of the nanocrystalline Nd_9.2Fe_61.64B_21.16Nb₈ alloy ribbons, are reported. It was shown that the rapidly solidified ribbons have partially amorphous structure and soft magnetic properties in the as-cast state. The heat treatment at temperatures higher than 923 K led to the growth of the hard magnetic Nd₂Fe₁₄B phase and the metastable Nd₂Fe₂₃B₃ phase. The Mössbauer confirmed that during annealing of the samples at temperature higher than 923 K the paramagnetic Nd_1+εFe₄B₄ phase was also formed. The microstructure consisting of mixture of constituent phases was observed with transmission electron microscopy (TEM). Furthermore, with increasing annealing temperature the decrease of the saturation polarization J_s was observed. The maximum values of coercivity _JH_c = 1175 kA/m was obtained for a sample annealed at 1023K. However, annealing at 1003 K resulted in the improvement of remanence polarization J_r = 0.35 T and the maximum energy product (BH)_max = 21 kJ/m³.