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) ~ 34 K. The estimated magnetic entropy change (-ΔS_M) for the Co₃O₄ nanoparticles suggests the unusual behavior in magnetic phase transformation of the Co₃O₄ nanoparticles. A normal magnetocaloric effect (MCE) at T ~ 44 K and inverse MCE at T ~ 34 K are observed. These results correlate the magnetocaloric properties to the magnetic phase transitions in the Co₃O₄ nanoparticle system.