Phase transformation, structure and magnetic properties of Nd-Fe-B-V alloys and their nitrides prepared by mechanical alloying

The structure and magnetic properties of mechanically alloyed (MA) Nd10Fe76B8-xV6+x series and their nitrides have been studied. With increasing V content, the magnetic main phase of Nd10Fe76B8-xV6+x series changes from the magnetic phase of Nd2Fe14B-type structure via a metastable Nd(Fe,V)(7) phase with TbCu7 structure to Nd(Fe,V)(12) phase with ThMn12 structure, The easy in-plane magnetization of Nd(Fe,V)(7) and Nd(Fe,V)(12) phases results in rather poor permanent magnetic properties. The V-containing Nd2Fe14B-type phase is partly decomposed upon nitrogenation. Because nitrogen enters into the interstitial sites of the TbCu7-type and ThMn12-type structures, their Curie temperatures are greatly enhanced. The easy magnetization of Nd(Fe,V)(7) with TbCu7, like Nd(Fe,V)(12) with ThMn12 structure, changes from easy in-plane to easy c-axis after nitrogenation. (C) 2000 Elsevier Science B.V. All rights reserved.