Magnetic properties of monodomain Nd-Fe-B-C nanoparticles

Abstract

Nanoparticles of Nd-Fe-B-C with their crystal structure similar to the Nd2Fe14B phase were generated in a carbon arc. With an average diameter of less than 40 nm, they are monodomain. They have a smaller room-temperature coercivity than would be predicted from the bulk magnetocrystalline anisotropy. However, their coercivity is greater than was previously observed in particles <5 μm prepared by spark erosion. While the carbon arc process is useful for making small carbon-coated particles which resist oxidation, here dispersion of excess Nd in the carbon matrix results in a significant paramagnetic signal. The dc demagnetization curves enable the paramagnetic and ferromagnetic contributions to be distinguished.