Microstructural and magnetic properties of core-shell Ni-Ce nanocomposite particles assemblies

Novel magnetic core-shell Ni-Ce nanocomposite particles (15-50 nm) are presented. SEM observation indicates a strongly ferromagnetic interacting order with chain-like features among Ni-Ce nanocomposite particle assemblies. Typical HREM image demonstrates that many planar defects (i.e. stacking faults) exist in large Ni core zone (10-45 nm); the innermost NiCe alloy and outermost NiO oxide exist in the thin shell layers (3-5 nm). Nano-diffraction patterns show an indication of well-defined spots characteristic and confirm the nature of this core-shell nanocomposite particles. Superparamagnetic relaxation behaviour above average blocking temperature (T_B =170K) for Ni-Ce nanocomposite particles assemblies have been exhibited, this superparamagnetic behaviour is found to be modified by interparticle interactions, which depending on the applied field; size distribution and coupling with the strong interparticle interaction. In addition, an antiferromagnetic order occurs with a Neél temperatu re T_N of about 11K due to Ce ion magnetic order ruction. A spin-flop transition is also observed below T_N at a certain applied field and low temperature.