Spin Canting of Maghemite Studied by NMR and In-Field Mossbauer Spectrometry

Abstract

Local probe techniques, (57)Fe in-field Mossbauer, and (57)Fe NMR spectrometries have been combined to describe the magnetic structure of maghemite nanoparticles of 39 (+/- 5) nm in size and commercial maghemite. Maghemite nanoparticles were obtained from oxidation of magnetite nanoparticles. Commercial maghemite consists of nanostructured rods, and the size of crystalline domain fairly compares to that of nanoparticles. The structure of the two samples is a partially disordered spine! structure. Both local probe techniques agree that Fe magnetic moments of octahedral and tetrahedral sites are canted in both systems. It was concluded that the canting originates not only from surface effects but also from the bulk resulting from the disordered spinel structure and the frustrated cationic topology, giving rise to reversed Fe moments.