Study of magnetic micro structures of Nd-Fe-B casting strips by using magnetic force microscope

Dy-Al substituted Nd-Fe-B strips were produced by strip casting technique. The magnetic microstructures of the 2-14-1 and Nd2Fe17(B) phases in both as-cast strips and the strips heat-treated at 1050 degreesC in Ar atmosphere, and the domain structures of the final sintered magnets have been revealed by using magnetic force microscope. The existence of fine Nd2Fe17(B) crystals with "plate-like" domains surrounded by 2-14-1 larger crystals with "ripple" domains was found in the as-cast strips. After heat treatment, spheric or columnar crystals of Nd2Fe17(B) phase were formed and the crystals of 2-14-1 phase became larger. The sintered magnets made from the strips heat-treated at 1050degrees C possess better magnetic properties: the remanence B-r similar to 1.42 T, the intrinsic coercivity H-cj similar to 995 kA/m, and energy density product (BH)(max) similar to 392 kj/m(3). (C) 2004 Elsevier B.V. All rights reserved.