Magnetic relaxation and submicrostructure of iron hydroxide precipitates in ionomer membrane

Abstract Ultrafine iron-containing particles precipitated in micropores of perfluorosulfonic ionomer membrane with a comb-polymer structure were studied by Mossbauer spectroscopy. To describe the experimental data, two mechanisms of magnetic relaxation were taken into account: collective magnetic excitations and superparamagnetic relaxation. Excellent agreement between the theoretical and experimental spectra was achieved with the assumption of a rather sharp temperature dependence of the pre-exponential factor of the superparamagnetic relaxation rate. It is supposed that this acceleration of the superparamagnetic relaxation is connected with the inhomogeneity of the ultrafine particle submicrostructure. A mechanism of inducing the acceleration of the relaxation, which is based on the reduction of the effective magnetic volume of the particles with increasing temperature, is proposed.