A Magnetite Colloid System Studied by Mössbauer Spectroscopy.

Magnetite loaded polyvinyl alcohol and polystyrol hydrogels were investigated by the help of 57Fe Mössbauer spectroscopy, XRD and transmission electron microscopy. Chemically cross-linked polyvinyl alcohol hydrogels filled with magnetite particles were prepared from magnetite sol obtained from FeCl2 and FeCl3 in aqueous solution. At near room temperature, the Mössbauer spectrum has hyperfine fields smaller than those characteristic of bulk magnetite. The temperature dependent collapse of the hyperfine splitting can be associated with paramagnetism rather than superparamagnetism. This indicates that a special magnetic interaction occurs between the small particles. This may be interpreted in the terms of dynamic magnetic phenomenon in fine particle magnetite incorporated into swollen elastic polymer network by supposing magnetic ordering of clusters (after Boquet et al.) created by high concentration of defects when the hyperfine field distribution is mainly influenced by the slow relaxation of the magnetic moments of the clusters. Nevertheless, the effect of monodispersity of the colloid system may also contribute to the unusual relaxation shape of the Mössbauer spectra. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]