The non-magnetic surface of magnetic particles in nanostructured glass ceramics studied by SANS

Nanosized crystallites of ferrimagnetic magnetite, Fe3O4, were prepared by heat treatment of a rapidly quenched silicate glass melt of composition 27. 4CaO-42.8SiO(2)-6.1B(2)O(3)-23.7Fe(2)O(3) (mol%). SANS experiments of sampl es annealed at different heat treatment conditions were performed to determ ine the evolution and nature of the nonmagnetic surface layer of the nanocr ystals. It is suggested that this layer is formed by the distorted crystall ine structure and thermally induced effects at the surface region and by th e formation of a segregation shell enriched with Fe2O3 and subsequent surfa ce oxidation of the Fe3O4 nanocrystals as well. (C) 2000 Elsevier Science B .V. All rights reserved.