ELECTRON-SPIN-RESONANCE STUDY OF NIFE2O4 NANOSOLIDS COMPACTED UNDER HIGH-PRESSURE

In this article, NiFe2O4 nanosolids are prepared by compacting nanopar ticles, synthesized by the coprecipitation method, under different pre ssures. The variations of structure and interface states of the NiFe2O 4 nanosolids with compacting pressures are studied by x-ray diffractio n and electronic spin resonance (ESR). It is found that the crystal st ructure of the nanosolids has not changed under pressure up to 6.0 GPa , but the linewidth and g-factor values of their ESR spectra increased significantly with increasing pressure up to 4.5 GPa and then decreas ed slightly with further increase of pressure. These variations are di scussed in terms of the changes of interparticle magnetic dipole inter action and superexchange interaction in NiFe2O4 nanosolids under diffe rent pressures. The experimental results suggest that 4.5 GPa is the o ptimum forming pressure, under which the NiFe2O4 nanoparticles can be compacted into a dense solid with their structure and nanoproperties s till preserved. (C) 1996 American Institute of Physics.