G. Goglio 1,2, K.-P. Hong 2, G. Demazeau 1,2, D.-Y. Jung 3
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1 Institut de Chimie de la Matiere Condensée de Bordeaux (ICMCB - UPR CNRS 9048), 87 Av. du Dr A. Schweitzer, 33608 PESSAC Cedex
2 Interface Hautes Pressions, E.N.S.C.P.B., 16 Av. Pey Berland, 33607 PESSAC Cedex
3 Department of Chemistry-BK21 and the Institute of Basic Science, SungKyunKwan University, Suwon 440-746, Korea
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Earth's crust compounds can be used as models to develop new functional materials. For example we have evidenced that it is possible to synthesize some new layered oxides which adopt a structure derivated from natural phyllosilicates such as biotite or phlogopite mica : the phyllosiloxides [1].

Phyllosiloxides have been developed in order to be used as interphase materials between fibre and matrix in composite materials. Although micas are oxidation-resistant and can easily cleave they cannot be used for such an application because their decomposition temperature is quite low (about 500C). Due to the fact that in phyllosiloxides all hydroxyls groups are replaced by oxygen, these new materials can resist to higher temperatures (about 1000C). Moreover phyllosiloxides can be developed for potential applications such as, for example, intercalation materials, catalysts...

The structure of phyllosiloxides can be described as the stacking along the c-axis of blocks which consist in octahedra layer embedded in two tetrahedra layers ; the different blocks are separated one from another by potassium planes. In this work we have tried to synthesize new phyllosiloxides where octahedral sites are occupied by transition metals : the octahedral magnetic layers are then separated by diamagnetic blocks which constitutes low dimensionality magnetic systems. We present here two materials K(Fe2+2Al3+)Si4O12 and K(Fe2+2 Fe3+)Si4O12 which have been synthesized via a solvothermal route [2].
Physico-chemical characterizations (Infrared spectroscopy, X-ray diffraction...) have allowed to confirm that these two new materials are isostructural with mica biotite and do not contain any hydroxyl groups. The study of magnetic properties has evidenced the coexistence of ferromagnetic and antiferromagnetic interactions in these new phyllosiloxides which is characteristic of bidimensional oxides magnetism.


[1] P. Reig, G. Demazeau, R. Naslain, Eur. J. of Solid State and Inorg. Chem, 32, 439-456, 1995
[2] G. Demazeau, J. Mater. Chem., 9, 15-18, 1999

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