The role of oxygen for improving magnetic properties and thermal stability of sintered (Nd,Dy)(Fe,Co)B magnets

Oxygen has traditionally been thought of as being detrimental to rare earth permanent magnet properties, even though it was shown to increase the corrosion resistance of NdFeB magnets. In this study, we have systematically investigated the effect of oxygen on the magnetic properties of various types of NdFeB magnets. The addition of appropriate amounts of oxygen to a NdDyFeB magnet system containing cobalt causes increases in the remanence and intrinsic coercivity. The temperature coefficient of coercivity and irreversible temperature losses are also improved (reduced). In alloy systems not containing cobalt, oxygen doping causes a reduction in intrinsic coercivity.