Improvements of Coercivity and Corrosion Resistance in Nd-Fe-Co-B Sintered Magnet by Addition of V or Mo

The structure, magnetic properties and corrosion resistance of sintered anisotropic Nd-Dy-Fe-Co-B- (V or Mo) permanent magnets are reported. Addition of a few atomic percent V or Mo was found to be beneficial in that it enhances the intrinsic coercivity (HcJ) without significantly sacrificing the remanence or maximum energy product, especially when a substantial amount of Co (approximately 5 at%) is present. Thus the addition of V or Mo together with Co serves to improve both corrosion resistance and temperature stability of the magnetic properties. Possible reasons for the enhancement of HcJby V and Mo are also discussed.