EFFECT OF INTERPARTICLE INTERACTIONS ON THE DYNAMICAL PROPERTIES OF GAMMA-FE2O3 NANOPARTICLES

The dynamical properties of gamma-Fe2O3 nanoparticles dispersed in a p olymer have been investigated bq means of AC susceptibility measuremen ts in a large frequency range (10 < nu < 10(4) Hz) and Mossbauer spect roscopy measurements. The frequency dependence of the blocking tempera ture, T-B, has been analysed for a series of samples with the same vol ume distribution and interparticle interactions of different strengths . An increase of the effective energy barrier with increasing interact ion strength has been observed unambiguously, in agreement with our mo del, based on a statistical calculation of the interaction energy for a disordered assembly of particles with volume distribution and easy a xes in random directions. (C) 1998 Elsevier Science B.V. All rights re served.