Study on the chemical co-precipitation synthesized CoFeO nanoparticle for magnetocaloric performance in the vicinity of superparamagnetic blocking temperature.

Nanoscaled magnetic cobalt ferrite (CoFeO) of approximately size 17 nm was synthesized via the co-precipitation method and then annealed at 600 °C. The resultant materials were taken for various magnetic characterizations. The X-ray diffraction pattern confirms the formation of the fcc type of cubic crystal structure. The ferrimagnetic phenomenon of the specimen was confirmed by the hysteresis loop, which is comparable to the slow relaxation sextet pattern of the Mӧssbauer study. Isomer shift, quadrupole splitting, hyperfine field, and Fe occupancy of various sites are also investigated from mӧssbauer spectroscopy. The frequency-dependent initial permeability has a comparatively high value up to a certain frequency range and then decreases drastically, whereas the imaginary part of complex permeability decreases sharply with the increase of frequency. The temperature-dependent magnetization ensures the presence of a superparamagnetic blocking temperature of 433 K. In the study of the magnetocaloric effect, isothermal magnetization measurements were carried out around the superparamagnetic blocking temperature, revealing a maximum entropy change of ΔS = 1.32 J/kg K and a relative cooling power (RCP) of 52.22 J/kg (H = 1.5 T) through the Maxwell approach. These outcomes emphasize the potential of CoFeO NPs for magnetic refrigeration at reduced temperatures with lower applied magnetic fields.