DYNAMICAL MAGNETIC-BEHAVIOR OF INTERACTING GAMMA-FE2O3 PARTICLES

The dynamical behavior of gamma-Fe2O3 particles dispersed in a polymer have been investigated by a.c. susceptibility and Mossbauer spectrosc opy measurements. The effect of interparticle interactions on the rela xation time is satisfactorily described by a superparamagnetic model w here the dipolar energy is determined by a statistical calculation for a disordered arrangement of particles with volume distribution and ea sy axes in random orientations. The results indicate that the single p article anisotropy energy is mainly determined by surface anisotropy a nd that the energy barrier increases with the interaction strength. (C ) 1998 John Wiley & Sons, Ltd.