The magnetic properties of annealed graphite-coated Ni and Co nanocrystals

Magnetic studies of graphite-coated nanocrystals of nickel and cobalt (5-50 nm) synthesized in a special fullerene are chamber are reported. Magnetization measurements as a function of temperature in the range 20-900/spl deg/C indicate the ferromagnetic nature of the nanocrystals. Upon heating and recooling of the nanocrystals a larger magnetization was measured, The dependence of room temperature M/sub s/, M/sub r/, and H/sub c/ of the nanocrystals on annealing temperature is reported. The data are consistent with increase in size of single domain particles, or transition of the nanocrystals from single domain to multi-domain due to particle size growth in the annealing process.