Probing the Defect Induced Magnetocaloric Effect on Ferrite/Graphene Functional Nanocomposites and their Magnetic Hyperthermia

Recently, the development of an alternative magnetic refrigerant for the conventional fossil fuels attracts the researchers. We discussed the structural defect-induced magnetocaloric effect (MCE) in Ni0.3Zn0.7Fe2O4/graphene (NZF/G) nanocomposites for the first time. Single-phase spinel ferrite nanocomposites with an average size of 7–11.4 nm were achieved by using the microwave-assisted coprecipitation method. The effect of graphene loading on the structural and magnetism of NZF/G nanocomposites was elaborated. Raman analysis proved that the interface interaction between NZF and graphene yielded different densities of structural defects. In view of magnetism, superparamagnetic NZF nanoparticles showed a magnetic entropy change (−ΔSMmax) of −0.678 J·kg–1 K–1 at 135 K, whereas the NZF/G nanocomposites exhibited superior −ΔSMmax at cryogenic temperatures and the defect-induced MCE change was indeed similar to the ID/IG intensity ratio. The nanocomposites exhibited different magnetic orderings between 5 and 2...