Magnetocaloric effect and critical behaviour in zinc doped cobalt ferrite nanoparticles

In this report a detail investigation of magnetocaloric properties and critical behaviour of Zn0.7Co0.3Fe2O4 nanoparticles synthesized via chemical co-precipitation method has been carried out. The Rietveld analysis of the XRD patterns of ZnxCo1-xFe2O4 (x = 0.5, 0.6, 0.7) nanoparticles confirm the crystal structure as Fd 3 m. The W-H plots confirm the presence of compressive micro strain inside the crystallites and a decreasing trend is observed with Zn doping. The magnetization measurements with temperature at 500 Oe applied field show that all the samples are superparamagnetic at room temperature. Coexistence of magnetic phases below room temperature is observed in Zn-0.6 and Zn-0.7 samples. The substitution of Zn2 thorn ions lead to decrease in blocking temperature (TB) as well as Curie temperature (TC). Analysis of magnetocaloric properties of the sample Zn-0.7 indicates a considerable amount of magnetic entropy change and relative cooling power. A significant inverse MCE is also expected to be observed due to anti-ferromagnetism at low temperature.