Gadolinium substitution effect on the thermomagnetic properties of Ni ferrite ferrofluids

Abstract

This work is focused on the characterization of Ni-ferrite nanocrystals and their subsequent doping with Gd, in an attempt to explore Gd inclusion in the thermomagnetic properties of prepared ferrofluids. Spinel ferritesNiFe2O4, and NiFe1.88Gd0.12O4 were prepared by the auto-combustion method. The substituted sample is obtained with a small amount of Gd inclusion and the excess appears as GdFeO3. The smallest nanoparticles of both samples were properly coated and dispersed in kerosene. Thermal conductivities of the produced ferrofluids were measured at 25 °C in a magnetic field. There is a significant enhancement in thermal conductivity of the ferrofluid prepared with NiGd ferrite with respect to the one with Ni ferrite, in presence of a magnetic field. This effect is directly related to the well-known magnetocaloric effect of Gd.