Local structure and magnetic properties of cubic iron oxide nanoparticles formed in zeolite as deduced using Mössbauer spectroscopy

摘要

Local structure and magnetic properties of cubic iron oxide nanoparticles as prepared in zeolite matrix have been studied in a detailed manner using Mössbauer spectroscopy. Superparamagnetic particles of cubic iron oxide are observed to be strongly bound in zeolite matrix. Annealing around 870 K is understood to result in detrapping of the bound nanoparticles. This leads to the onset of coarsening of the nanoparticles thus resulting in an appearence of a broad sextet characterised by a low hyperfine field. On the otherhand, the occurrence of the sextet, due to the onset of coarsening of the bare cubic iron oxide superparamagnetic nanoparticles, has been observed subsequent to annealing around 520 K. Linewidth and quadrupole splitting corresponding to the fraction of 57Fe absorbers associated with superparamagnetic particles are shown to be sensitively dependent upon the annealing temperature with respect to detrapping and aggregation of nanoparticles formed in zeolite.