Effect of minor grain boundary additives on the magnetic properties of NdFeB magnets

Cobalt has been known as an element to increase the Curie temperature but to decrease the coercivity of (Nd,Dy)FeB magnets. Because of this negative effect, various elements have been added to increase the coercivity but at the expense of remanence and/or Curie temperature. The combined addition of cobalt and small amounts of copper to (Nd,Dy)FeB alloy was found to substantially increase the coercivity without B/sub r/ and T/sub c/ reduction. As a result, the temperature stability and corrosion resistance have substantially improved without sacrificing any magnetic performance.