Resonant microwave cavity of amorphous ribbons

In this study we report microwave experiments on the amorphous ribbon Fe4.6Co70.4Si15B10 using the usual setup for magnetic resonance experiments at 9.4 GHz to observe the cavity response. Several samples cut from the same tape were annealed, either in the presence or in the absence of a magnetic field. For each sample the magnetization and magnetoimpedance (MI) curves were obtained, with MI ratios between 1% and 40%. The magnetic resonance spectrum consists of the usual ferromagnetic line and an anomalous low field cavity response for H<100 Oe. The shape of this low field signal depends on the thermal treatment and on the orientation of the external field. We believe that this signal is in part a ferromagnetic peak but it also carries information of the skin-depth changes with a sweeping magnetic field. (C) 1996 American Institute of Physics.