Complex high-frequency magnetization dynamics and magnetoimpedance in thin films

High-frequency differential magnetic permeability and magnetoimpedance measurements were performed in Fe73.5CU1Nb3Si13.5B9 as-made and annealed thin films at frequencies up to 1.8 GHz. The results show complex dynamical properties characterized by multiple ferromagnetic resonance modes at relatively low frequencies for the amorphous as-made sample. After the thermal treatments, the resonance frequencies increase drastically exceeding the upper limit of 1.8 GHz for our equipment. This increase can possibly associated to higher local magnetic fields that are, in turn, associated to the formation of nanocrystalline grains randomly oriented. (c) 2006 Elsevier B.V. All rights reserved.