Thin film nanocomposite Nd2Fe14B/αFe magnets

Nanocomposite Nd2Fe14B/alpha-Fe magnets were prepared by either sputtering from cast alloy targets with increased Fe content, or by depositing successively from a Nd20Fe70NbB9 and an iron target in a multilayer fashion. For the optimally annealed samples magnetic data indicate the existence of a hard phase that is exchange-coupled with the soft phase (alpha-Fe) grains. These samples showed remanence enhancement. For longer annealing times alpha-Fe clustering leads to decoupling of the soft phase. The TEM studies showed that in this case the grain size exceeds the theoretically predicted size (of about 10 nm)for optimum coupling between the two phases. By depositing in an alternating layer structure, higher coercivities were obtained due to the advantage of controlling the softphase content as well as the grain size by the individual layer thickness. (C) 1998 Acta Metallurgica Inc.