Magnetic Properties of Co3O4 Nanoparticles Fabricated by Chemical Synthesis

Nanoparticles of cobalt oxide (Co
₃
O
₄
), 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 Co
₃
O
₄
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 Co
₃
O
₄
nanoparticles suggests the unusual behavior in magnetic phase transformation of the Co
₃
O
₄
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 Co
₃
O
₄
nanoparticle system.