Magnetocaloric Effect, Dielectric Relaxor Behavior, and Evidence for Direct Magnetodielectric Behavior in Ni_0.6Zn_0.4Al_0.5Fe_1.5O₄ Ceramics for High-Temperature Applications

This study investigates the magnetic properties of Ni_0.6Zn_0.4Al_0.5Fe_1.5O₄ ceramics as a function of varying temperature. The results show that the sharp change in magnetization at Curie temperatures produces a reasonable magnetic entropy change (ΔS_M). The Ni–Zn–Al ferrite is, therefore, predicted to work better than other spinel ferrites with higher efficiencies. Near the second-order transition, the critical exponents are derived from the magnetic entropy change’s field dependency. Their values are close to the mean field model. The reliability of the calculated exponents is confirmed by using scaling theory. The temperature dependence of the dielectric constants shows the presence of phase transitions. In fact, the local disorder provides a frequency that is dependent on relaxor ferroelectric-like behaviors, which is a significant finding in the search for new lead-free relaxor materials. The modified Curie–Weiss law and the Lorentz and Gaussian-type relationships are used to analyze the diffuse phase transition. A correlation between dielectric and magnetic behaviors near the magnetic phase transition temperature (direct observation magnetodielectric effect) is established. Based on these findings, the Ni_0.6Zn_0.4Al_0.5Fe_1.5O₄ ceramic appears to be a promising candidate for multifunctional device applications.