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

We report on a detailed study of the structural, magnetic and magnetocaloric properties of Zn0.6-xNxCu0.4Fe2O4 (0 <= x <= 0.6) ferrite nanopartides which are prepared using the Pechini sal-gel technique. The X-ray diffraction results indicate that the ferrite samples have a cubic spinet 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 T-C with increasing Ni content, from 305 K for x = 0 to 705 K for x = 0.4 (for x = 0.6 sample, the T-C value is greater than 750 K). The magnetic entropy change was also studied through the examination of measured magnetic isotherms M(H, T) near T-C. With increasing Ni content, the maximum magnetic entropy change vertical bar Delta S-M(max)vertical bar 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 Delta H = 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. (C) 2015 Elsevier B.V. All rights reserved.