Magnetic and Mossbauer spectroscopy studies of CoFe2O4/CoFe2nanocomposites

CoFe2O4/CoFe(2)nanocomposites with exchange coupling behavior have been obtained from a two-step process. First, CoFe(2)O(4)nanoparticles with size of 11 nm were synthesized using a co-precipitation method. And second, the as-synthesized CoFe(2)O(4)nanoparticles were reduced under mixed gas (Ar 95% + H(2)5%) for 1 h at different temperatures. The structure, phase, particle size, morphology, and magnetic properties with the reduction temperature were studied. X-ray diffraction and Mossbauer spectroscopy results show the whole process from pure CoFe(2)O(4)hard magnetic phase to pure CoFe(2)soft magnetic phase when the reduction temperature increases from 400 to 700 degrees C, and CoFe2O4/CoFe(2)hard/soft nanocomposites are obtained at 500 and 600 degrees C. Magnetic measurement result show there is a stronger exchange coupling interaction between CoFe(2)O(4)and CoFe(2)for the sample reduced at 500 degrees C, but not in the sample reduced at 600 degrees C. A giant 76% enhancement of the maximum magnetic energy product (BH)(max)compared with pure CoFe(2)O(4)will be of technological significance in the future.