Magnetic excitations in ferromagnetic glasses

Abstract We have studied theoretically (including computer simulations) dynamical magnetic properties of aggregates of ferromagnetic amorphous nanogranules in the presence of direct exchange between the neighboring granules and random anisotropy fields. It was shown that in such structures there still exist delocalized magnetic excitations similar to magnons in the bulk materials, although at much lower frequencies. The excitations at high frequencies are localized within the corresponding granules. The details of spectrum of these excitations (including structural factors) are discussed.