Improved corrosion resistance and magnetic properties of Nd-Fe-B-type sintered magnets with Mo and Co

Abstract

A few atomic percent addition of Mo considerably improves the intrinsic coercivity (HcJ) of Nd-Dy-Fe-Co-B sintered magnets if the Mo content is optimized against B content. It is shown that upgrading of the magnet can be realized by decreasing both Mo and B contents, keeping the optimum Mo-B relation. Dependence of corrosion resistance of both uncoated and aluminum-coated magnets on Co and Nd contents are studied and significant improvement of the corrosion resistance is attributed to formation of an Nd-Co compound, probably Nd3Co.