Wasp-waisted like magnetic behavior of nanocrystalline CoFe2O4 at 5K

Nanocrystalline cobalt ferrite (CoFe2O4) was synthesized through a sol-gel reaction route and characterized by powder XRD and SQUID magnetometry measurements. Rietveld profile refinement of XRD pattern confirmed formation of single phase nanocrystalline CoFe2O4 in the fcc symmetry with an average particle size of ~16nm. CoFe2O4 display soft ferrimagnetic behavior at 300K with a saturation magnetization of ~74emu/g, remanence of ~27emu/g and coercivity of 1.66kOe. M-H curve recorded at 5K showed wasp-waisted hysteresis loop with a saturation magnetization of 80emu/g, very high coercivity of 13.52kOe and 59emu/g remanence. Temperature dependence of ZFC and IFC modes of magnetization are suggestive of superspin glass state below 100K in CoFe2O4 nanoparticles. Superposition of superspin glass and superparamagnetic phases in the CoFe2O4 lattice at 5K leads to the wasp-waisted hysteresis loop.