Structural, magnetic and magnetocaloric properties, and analysis of MCE using the mean-field theory of Mg–Co ferrite with Ni substitution

The effects of Ni substitution on structural, magnetic and magnetocaloric properties of Mg0.6Cu0.4−xNixFe2O4 (x = 0 and 0.2) ferrites synthesized via sol–gel method has been investigated in this work. XRD patterns confirm the formation of cubic spinel structure with \(Fd\bar {3}m\) space group. Both samples present ferromagnetic (FM)–paramagnetic (PM) phase transitions of second order type with an increment of Curie temperature (TC) from 630 to 670 K for x = 0 and 0.2, respectively. The addition of Ni leads to the increase of the values of maximum magnetic entropy change (\(- \Delta S_{M}^{{max}}\)) and relative cooling power (RCP) from (1.09 J kg−1 K−1 and 136 J kg−1, for x = 0) to (1.38 J kg−1 K−1 and 173 J.kg−1, for x = 0.2) for an applied magnetic field of H = 5 T. The magnetic entropy changes for the samples were also estimated by using the mean-field scaling theory, and the results show a difference between the theoretical and experimental values.