The Preparation and Electron Spin Resonance Study of NiFe2O4 Nanosolids under High Pressure

In the present paper, the NiFe2O4 nanoparticles which were synthesized by the method of reserve drop coprecipitation, then compacted into nanosolids under different pressures. The variation of structure and interfacial states in NiFe2O4 nanosolids under different pressures are studied by XRD and ESR measurement for the first time. The experimental results indicate that, the structure of nanosolids has not changed obviously under the pressure up to 6.0 GPa; but the linewidth and g-factor values of their ESR spectra would increase significantly with increasing pressure up to 4.5 GPa and then turn to decrease under higher pressures. These variations could be interpreted by the change of magnetic interaction in the NiFe2O4 nanosolids under different pressures. These experimental results suggest that 4.5 GPa is the best forming pressure, under which the NiFe2O4 nanoparticles can be compacted into densest solid but their structure and nano-properties have not been destroyed.