Anomalous magnetic properties in Co3O4 nanoparticles covered with polymer decomposition residues

Co3O4 nanoparticles with and without covering of residues from the decomposed polymer at the surface have been fabricated, respectively. It has been revealed that anomalous magnetic properties of the nanoparticles covered with the residues deviate greatly from those of the ones without residues. In comparison with the "naked" Co3O4 nanoparticles, for the "covered" sample, the saturation field, coercivity, loop shift and average permanent magnetic moments per Co3O4 particle are enhanced remarkably. It is believed that the anomalous magnetic properties and their significant difference are caused by the presence of residues at the surface, consistent to the reported results in literature. (C) 2004 American Institute of Physics.