Vacancy ordering in nanosized maghemite from neutron and X-ray powder diffraction

Powder neutron and X-ray diffraction patterns of nanocrystalline needle-shaped maghemite (gamma-Fe2O3) particles with average size 240 nm x 30 nm show the presence of superstructure peaks indicating a long-range ordering of the cation vacancies. The crystallographic parameters, the characteristics of the tetragonal distortion, and the vacancy distribution were determined in space group P4(1)2(1)2 by multiprofile Rietveld refinement.