Effect of erbium substitution on the permanent magnet properties of sintered (Nd,Dy)-(Fe,Co)-B

The effects of dysprosium and erbium on the temperature dependence of remanence and intrinsic coercivity in Co-containing Nd-Fe-B were studied. Sintered magnets were prepared and demagnetization curves measured at temperatures between -50 and 200°C. Curie temperatures and irreversible losses of open-circuit flux on heating were also determined. Dy increases the coercivity while Er decreases it. Both Dy and Er can improve the temperature coefficient of remanence and even that of the intrinsic coereivity. Simultaneous substitution of these two heavy rare earths can be beneficial for magnets used below 150°C, but Er lowers H c and increases the irreversible loss at higher temperatures.