DYNAMIC MAGNETIC-BEHAVIOR OF INTERACTING GAMMA-FE2O3 NANOPARTICLES DISPERSED IN EPOXY-RESIN

The dynamical behaviour of gamma-Fe2O3 particles synthesized by a micr oemulsion route, with an average diameter of 7 nm and dispersed in an epoxy-resin at different concentrations, has been investigated by a.c. magnetic susceptibility measurements (8 < f (Hz) < 1000). For the mos t diluted sample, the frequency dependence of the temperatures of the maximum of the in-phase susceptibility follow an Arrhenius law with ph ysical tau(0) value (10(-10) s). Unphysical, much lower values are fou nd fair samples consisting of interacting particles. The results are e xplained by accounting for the change of interparticle distance and nu mber of particle neighbours.