MAGNETIC-PROPERTIES OF MONODOMAIN ND-FE-B-C NANOPARTICLES

Nanoparticles of Nd-Fe-B-C with their crystal structure similar to the Nd2Fe14B phase were generated in a carbon are. With an average diamet er of less than 40 nm, they are monodomain. They have a smaller room-t emperature coercivity than would be predicted from the bulk magnetocry stalline anisotropy. However, their coercivity is greater than was pre viously observed in particles <5 mu m prepared by spark erosion. While the carbon are process is useful for making small carbon-coated parti cles which resist oxidation, here dispersion of excess Nd in the carbo n matrix results in a significant paramagnetic signal. The de demagnet ization curves enable the paramagnetic and ferromagnetic contributions to be distinguished. (C) 1996 American Institute of Physics.