Microstructural, Magnetic, Magnetocaloric, and Electrical Properties of Ni0.4Mg0.3Cu0.3Fe2O4 Ferrite Prepared Using Sol–Gel Method

Detailed investigations of the microstructural, magnetic, magnetocaloric, and electrical properties of Ni 0.4 Mg 0.3 Cu 0.3 Fe 2 O 4 ferrite synthesized by sol-gel method have been investigated. XRD pattern indicates that sample has cubic spinel structure with Fd 3 ̄ m symmetry. The cation distribution of the sample has been determined by Rietveld refinement. Temperature dependence of magnetization shows that sample exhibits a second-order PM to FM phase transition at the Curie temperature T C = 690 K. From the M ( μ 0 H , T ) data, we found that the maximum entropy change ΔS M max reaches value of about 1.56 J kg − 1 K − 1 and relative cooling power (RCP) of 136 J kg − 1 at μ 0 H = 5 T. From electrical conductivity curves, the estimated value of the activation energy is equal to 0.349 eV. The Nequist diagram at different temperatures reveals that the grain boundary contribution is responsible to the conduction process for the studied sample.