ON THE ROLE OF DIPOLAR COUPLING IN THE MAGNETIZATION REVERSAL PROCESSIN HARD-SOFT NANOCOMPOSITE MAGNETS

We present simulations of hysteresis curves of simple nanocomposite ha rd soft magnets. The coercivity tvas investigated for triads of hard-s oft-hard grains having different magnetization-to-anisotropy ratios m = mu(0)M(s)(2)/2K. The systems were described by a micromagnetic model faking into account anistotropy, Zeeman, exchange and dipolar energie s and their dynamics were followed by a Monte Carlo Metropolis algorit hm. The exchange-to-anisotropy ratio a = Ad(-2)/K was assumed large en ough to provide good intergrain coupling. Then, for small m values in the hard grain, the propagation of the reversal process into those gra ins occurred through a Neel-like wall, whereas, for m > 0.25, a Bloch- like wall was observed.