Enhanced coercive force of Nd-Fe-B thin films by the introduction of a Cr underlayer

We investigated the influence of a Cr underlayer on the structure and magne tic properties of Nd-Fe-B thin films which were produced by a conventional rf sputtering method, The thickness of the underlayer and the substrate tem perature were varied from 0 to 5000 Angstrom and from room temperature to 6 70 degrees C, respectively. It was found that the thickness of the underlay er material and the substrate temperature strongly influenced the crystal o rientation and magnetic properties. The main crystalline phase was Nd2Fe14B , whose tetragonal c-axis was aligned perpendicularly to the film plane. A high coercive force (H-c = 3.7 kOe) was achieved using the following condit ions: Cr underlayer with a thickness of 500 Angstrom and a substrate temper ature of 650 degrees C. From TEM observation, this enhanced coercive force is thought to be attributable to a modification of the columnar structure. (C) 1998 Elsevier Science S.A. All rights reserved.