Assessment of the critical behavior near the FM to PM phase transition in cubic Ni0.3−xCuxZn0.7Fe2O4 spinel ferrite

•Results show that the ferromagnetic–paramagnetic transition is of second order.•The critical exponents (β, γ and δ) values for Zn0.7Ni0.3−xCuxFe2O4 are close the 3D-Heisenberg model.•The obtained values of critical exponents satisfying the scaling theory. In this study, we report a thorough examination of the critical behavior of the cubic Ni0.3−xCux Zn0.7Fe2O4 (x = 0.0, 0.1 and 0.2) spinel ferrite which are crystallized with different irregular shapes of particle size (spherical,polygonal and cubic). The magnetic transition is ferromagnetic to paramagnetic state for all Cu-doped compounds. Different theoretical analyses, as the modified Arrott plot, Kouvel–Fisher method, and critical isotherm, have been used to identify the values of the ferromagnetic transition temperature TC, and the critical exponents of β, γ and δ. All the obtained values of critical parameters were found to be close to the 3D-Heisenberg theoretical model, which implies short-range magnetic interactions in Cu-doped compounds. The reliability of critical parameters was further checked through different methods, such as the Widom scaling relationship and the magnetic equation.