Spin-Relaxation of NiO Encapsulated Gd2O3 Core–Shell Nanoparticles

Abstract

Nickel oxide encapsulated gadolinium oxide (Gd2O3/NiO) core–shell nanoparticles (Nps) has been synthesized by polyol method and analyzed by transmission electron microscopy. The particle size is found to vary from 25 to 35 nm. Raman spectra show the gadolinium oxide core material peaks are found to be diminished by the mass effect of the NiO shell material. The dynamics of the magnetic moment has been studied with the help of temperature dependent electron paramagnetic resonance (EPR) spectroscopy. Peak-to-peak line width (ΔH pp) value of the EPR spectra increases with decreasing temperature. Temperature dependence of line width shows the dominance of spin–lattice relaxation in these systems, and it can be used as T 1 contrast agent. Spin number estimated from EPR studies increases with the decrease of the temperature. The interfacial exchange coupling between the core and shell region is found to be existing at very low temperatures as determined by EPR studies in this non-magnetic/antiferromagnetic (NM/AFM) core/shell nanosystem. The effects of the temperature on the magnetic properties of the Gd2O3/NiO core/shell NPs and the underlying mechanism have been discussed.