Spin Relaxation of Gd2O3/NiFe2O4 Core-Shell Nanoparticles

Nickel ferrite encapsulated gadolinium oxide (Gd2O3/NiFe2O4) core-shell nanoparticles (NPs) has been synthesized by polyol method and analyzed by transmission electron microscope (TEM). The particle size is found to vary from 10 nm to 24 nm. The dynamics of magnetic moment has been studied with the help of temperature dependent electron paramagnetic resonance (EPR) spectroscopy. Peak-to-peak line width (Delta H-pp) and 'g' value of the EPR spectra are found to increase with the decrease of temperature. The sample has the lowest value of both these parameters at room temperature, which indicates that Gd2O3/NiFe2O4 shows minimum loss and is suitable for high frequency devices. Temperature dependence of line width shows the dominance of spin-spin relaxation in this system. Spin number estimated from EPR studies increases while the spin-spin relaxation time (T-2) decreases with decreasing temperature. The effect of temperature on the magnetic properties of the Gd2O3/NiFe2O4 core/shell NPs and the underlying mechanisms have been discussed.