Structural, magnetic and magnetocaloric properties of Zn0.6 − xNixCu0.4Fe2O4 ferrite nanoparticles prepared by Pechini sol-gel method

• Zn0.6 − xNixCu0.4Fe2O4 ferrites were prepared using Pechini sol-gel technique.
• The samples crystallize in the cubic spinel type structure (Fd3¯m space group).
• The samples exhibit a second-order PM–FM phase transition at TC.
• The doping of Ni increases the TC and |ΔSMmax| values.

We report on a detailed study of the structural, magnetic and magnetocaloric properties of Zn0.6 − xNixCu0.4Fe2O4 (0 ≤ x ≤ 0.6) ferrite nanoparticles which are prepared using the Pechini sol-gel technique. The X-ray diffraction results indicate that the ferrite samples have a cubic spinel structure without any impurity phase. Structural analysis shows that the lattice constant and the unit cell volume decrease with increasing Ni content. Magnetization measurements and Arrott plot analysis reveal a second-order paramagnetic (PM) -ferromagnetic (FM) phase transition for x = 0, 0.2 and 0.4 samples, with an increase in Curie temperature TC with increasing Ni content, from 305 K for x = 0 to 705 K for x = 0.4 (for x = 0.6 sample, the TC value is greater than 750 K). The magnetic entropy change was also studied through the examination of measured magnetic isotherms M(H, T) near TC. With increasing Ni content, the maximum magnetic entropy change |ΔSMmax| has increased from 1.16 J kg− 1 K− 1 (for x = 0) to 1.61 J kg− 1 K− 1 (for x = 0.4) for a field change ΔH = 5 T. Respectively, the relative cooling power (RCP) values are relatively high which makes our samples promising materials to be used in ecologically friendly magnetic refrigeration technology.

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