Title : Modeling the magnetocaloric effect and critical behavior near the ferromagnetic-paramagnetic transition temperature in Zn0.5-xNixMg0.5Fe2O4 (x = 0, 0.125 and 0.250) spinel ferrites
Abstract:
The Landau model allows to estimate the Landau coefficients A(T), B(T) and C(T), which can be determined by fitting the Arrott plots in Zn0.5-xNixMg0.5Fe2O4 (x = 0, 0.125 and 0.250) ferrites. These coefficients are derived to determine –ΔSM (T) curves. A good correlation between –ΔSM (T) curves determined using Landau theory and the experimental curves estimated using the Maxwell relation was found. Then, the second order magnetic phase transition in Zn0.5-xNixMg0.5Fe2O4 compounds was investigated. The critical properties of ferrites prepared by the double ceramic sintering process were investigated. Critical behavior near the FM-PM phase transition was studied from the magnetic data, through various techniques such as the modified Arrott plots (MAP), the Kouvel-Fisher method (KF) and critical isotherm (CI) analysis. The determined critical parameters were found to be close to the value of the mean-field theory. On the other hand, the validity of the critical parameters was confirmed by the Widom scaling relation.
