Dependence of structural and magnetic properties of CoFe2O4/SiO2 nanocomposites on annealing temperature and component ratio

摘要

Cobalt ferrite (CoFe2O4) nanoparticles embedded in amorphous silica can be synthesized by using tetraethylorthosilicate (TEOS) and metallic nitrates as precursors. A well-established silica matrix network provides nucleation locations for CoFe2O4 nanoparticles, thus confining their growth and aggregation. The structural and magnetic properties show strong dependence on the variation of particle size caused by annealing temperature and CoFe2O4 ratio, resulting in higher crystallization, saturation magnetization M-s and remanent magnetization M-r as the annealing temperature and CoFe2O4 ratio increase. But the variation of coercivity H-c is not in accordance with that of M-s and M-p indicating that H-c is not determined by the size of CoFe2O4 nanoparticles only. The realization of the adjustable particle sizes and the controllable magnetic properties makes the applicability of CoFe2O4 even more versatile. (C) 2008 Elsevier B.V. All rights reserved.