A magnetic and compositional study of the disproportionated stage of the solid-HDDR process in NdFeB-type materials

A thinned sample of Nd12.8Fe69.2Co11Ga1B6 after the disproportionation stage of the solid-HDDR process has been examined using advanced transmission electron microscopy techniques. High resolution X-ray mapping is particularly useful for showing the distribution of all elements with the exception of B. Elemental maps show clearly that during the disproportionation reaction, Co and Ga partitioned into the alpha-Fe and not into the NdH2. Domain observations using Lorentz microscopy revealed irregular domain walls whose location was influenced by the non-magnetic NdH2 inclusions. The walls moved easily under small applied magnetic fields in a series of discrete jumps. The behaviour was consistent with that of a soft magnetic material with low anisotropy, and differed markedly from that of the recombined material. (C) 1998 Elsevier Science S.A. All rights reserved.