Magnetic Properties of Co3O4 Nanoparticles Fabricated by Chemical Synthesis

Nanoparticles of cobalt oxide (Co3O4), of size 4.2 nm, were fabricated by heating Cobalt (Co) nanoparticles synthesized using dimethyl sulfoxide solvent. The temperature dependence of magnetization for field cool and zero field cool processes of Co3O4 nanoparticles shows the bifurcation at 44 K. A cusp is observed at 1 T and higher applied fields indicating antiferromagnetic behavior in the system with the Neel temperature (T-N) similar to 34 K. The estimated magnetic entropy change (-Delta S-M) for the Co3O4 nanoparticles suggests the unusual behavior in magnetic phase transformation of the Co3O4 nanoparticles. A normal magnetocaloric effect (MCE) at T similar to 44 K and inverse MCE at T similar to 34 K are observed. These results correlate the magnetocaloric properties to the magnetic phase transitions in the Co3O4 nanoparticle system.