Magnetic sol-gel derived poly(oxyethylene)-siloxane nanohybrids
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Data
2002-01-01
Autores
Amaral, V. S.
Carlos, L. D.
Silva, N. J O
De Zea Bermudez, V.
Dahmouche, K. [UNESP]
Santilli, Celso Valentim [UNESP]
Craievich, A. F.
Palacio, F.
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Resumo
The magnetic and structural properties of sol-gel derived organic/inorganic nanocomposites doped with Fe(II), Fe(III), Nd(III) and Eu (III) ions are discussed. These hybrids consist of poly(oxyethylene)-based chains grafted onto siloxane nanodomains by urea cross-linkages. Small angle X-ray scattering data show the presence of spatial correlations of siloxane domains embedded in the polymer matrix. The magnetic properties of rare-earth doped samples are determined by single ion crystal-field-splitted levels (Eu3+ J=0; Nd3+ J=9/2) and the small thermal irreversibility is mainly associated to structural effects. Fe2+ -doped samples behave as simple paramagnet with residual antiferromagnetic interactions. Fe3+-doped hybrids are much more complex, with magnetic hysterisis, exchange anisotropy and thermal irreversibility at low temperatures. Néel temperatures increase up to 14K for the highest (∼5.5%) Fe3+ mass concentration.
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Antiferromagnetism, Crosslinking, Doping (additives), Magnetic anisotropy, Magnetic hysteresis, Paramagnetic materials, Polyethylene glycols, Sol-gels, X ray scattering, Nanohybrid materials, Nanostructured materials
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Materials Research Society Symposium - Proceedings, v. 726, p. 143-148.