Magnetic phase transition and magneto-dielectric analysis of spinel chromites: MCr2O4 (M = Fe, Co and Ni)

In this work, we present magnetic phase transition temperatures and magneto-dielectric coupling in MCr2O4 (M = Fe, Co and Ni) ceramics, synthesized using sol-gel auto-combustion route. In order to develop their respective crystalline textures, all these chromites were calcined at 650 °C for 2 h. X-ray diffraction patterns confirmed that FeCr2O4 had a rhombohedral structure while NiCr2O4 and CoCr2O4 exhibited a spinel-type cubic structure. The presence of relevant elements in the specific stoichiometric ratios was confirmed using energy dispersive X-ray spectroscopy. The shapes and sizes of the grains for all the samples were determined using the images obtained from a field emission scanning electron microscope. Temperature dependent magnetic analysis have shown that FeCr2O4, CoCr2O4 and NiCr2O4 are ferromagnetic at 5 K and their magnetic phase transition temperatures were measured as 80, 83 and 90 K, respectively. Spin-orbit interference was also studied through magneto-dielectric coupling for these chromites using a modified impedance analyzer set-up.