Origin of high-coercivity in nanocomposites by single-precursor sol-gel method

0392057 - ÚACH 2014 GB eng J - Journal Article
Poltierová Vejpravová, J. - Brázda, Petr - Mantlíková, A. - Nižňanský, D. - Rohovec, Jan
Origin of high-coercivity in nanocomposites by single-precursor sol-gel method.
Journal of Physics Conference. Roč. 266, 012123 (2011). ISSN 1742-6588.
[International Symposium on Advanced Magnetic Materials and Applications (ISAMMA) /2./. Sendai, 12.07.2010-16.07.2010]
Institutional research plan: CEZ:AV0Z40320502; CEZ:AV0Z30130516
Keywords : magnetic-properties * nanoparticles * epsilon-FE2O3 * nanocrystals
Subject RIV: CA - Inorganic Chemistry

We have fabricated high-coercivity nanocomposites constituted of Fe2O3 or CoFe2O4 nanocrystals embedded in amorphous silica matrix by a single-molecule precursor sol-gel method. Our approach enables smooth variation of the Fe(Co) : Si ratio up to 40 weight % of the magnetic phase, resulting in high density nanocomposite. Final crystallite size and phase composition was adjusted by subsequent heat treatment. The Fe2O3/SiO2 samples annealed at 1000 and 1100 degrees C revealed coercivity, H-c similar to 2 T at 300 K due to formation of the metastable epsilon-Fe2O3 phase. The CoFe2O4/SiO2 composites exhibit enhancement of the H-c value with increasing annealing temperature. Origin of the large coercivity in the two types of the magnetically hard nanocomposites will be discussed.
Permanent Link: http://hdl.handle.net/11104/0221031