The exchange coupling interaction in CoFe2O4/Fe3O4 hard and soft magnetic nanocomposites

Abstract

Nanocomposites containing hard and soft magnetic phases have attracted a lot of attentions for their excellent magnetic properties. In this work, the hard and soft magnetic nanocomposites CoFe2O4/Fe3O4 were prepared using a co-precipitation method, and the structural, morphological and magnetic characterizations were researched. The X-ray diffraction revealed the formation of spinel ferrites, and the average crystallite sizes were about 15–18 nm. When the concentration of soft ferrite Fe3O4 increased, there were some bigger spherical and cubic-like particles in the images of the field emission scanning electron microscopy and transmission electron microscopy. Energy dispersive X-ray analysis, Mössbauer spectroscopy and magnetic measurement demonstrated the co-existence of CoFe2O4 and Fe3O4 phases in nanocomposites, and the improvement of the magnetic properties indicated there was a good exchange-coupling interaction between the hard and soft magnetic phases. For the sample with a mass ratio of CoFe2O4 to Fe3O4 being 1:1, the value of (BH)max at 300 K and 77 K are about 35% and 842% higher than those of the pure CoFe2O4, respectively.