Actas de congresos
Magnetic sol-gel derived poly(oxyethylene)-siloxane nanohybrids
Fecha
2002-01-01Registro en:
Materials Research Society Symposium - Proceedings, v. 726, p. 143-148.
0272-9172
10.1557/PROC-726-Q6.22
2-s2.0-0036441705
5584298681870865
0000-0002-8356-8093
Autor
Universidade de Aveiro
Universidade Estadual Paulista (Unesp)
Universidade de São Paulo (USP)
Univ. de Zaragoza
Institución
Resumen
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.