Investigations on the magnetocaloric effect and critical behavior of CoGa1.2Fe0.8O4 spinel ferrite

The critical behavior of (NixZn1-x)Fe2O4 ferrites doped with Mg, Cu and Gd at Ni and Zn sites has been widely reported before. Among them, the types of magnetic interaction in these ferrites are observed between the 3DHeisenberg and mean-field models, satisfying the triple critical mean-field model and the 3D-Heisenberg model, and beyond any theoretical models in some cases. In this work, the critical behavior of CoGa1.2Fe0.8O4 with Ga-doped at the Fe-sites has been studied. The main results are as follows: the sample has a second-order magnetic phase transition at a temperature of Tc = 210 K. The Rhodes-Wolfarth ratio RWR sz-.11 means that the magnetization is due to the contribution of local magnetic moments. The critical parameters obtained by the modified Arrott method (and the Kouvel-Fisher one) were beta = 0.498 (0.509), gamma = 1.005 (0.924) and delta = 3.018 (2.815). The critical exponents together with the exchange distance J(r) proportional to r-4:5082 confirm that the magnetic interaction in CoGa1.2Fe0.8O4 belongs to the mean-field model (beta = 0.5, gamma = 1 and delta = 3), indicating that CoGa1.2Fe0.8O4 has a long-range ferromagnetic interaction, which is different from the magnetic interaction in the (NixZn1-x)Fe2O4 ferrites doped at Ni and Zn sites.

Automated summary

The critical behavior of CoGa1.2Fe0.8O4 ferrites with Ga-doped at the Fe-sites has been studied, revealing its long-range ferromagnetic interaction, which is different from the magnetic interaction in the previously studied NixZn1-xFe2O4 ferrites.