Transition from quasistatic to ferromagnetic resonance regime in giant magnetoimpedance

Detailed measurements of giant magnetoimpedance (GMI) in an amorphous ribbon and a magnetic/nonmagnetic multilayer are presented for frequencies up to 3 GHz. Through this frequency range, the transition from quasistatic to dynamic regime of GMI can be clearly distinguished, due to the appearance of the ferromagnetic resonance (FMR). The unambiguous experimental evidence presented mediates between conflicting interpretations of GMI: the ones that assume the existence of FMR even for low frequencies and the ones that consider that it is irrelevant. The frequency at which the transition takes place is shown to be related with the width of the resonance, which is substantially different for both samples. It is concluded that the large increase of permeability caused by the ferromagnetic resonance can be advantageous for GMI-based devices only for samples with a small, very well-defined perpendicular anisotropy. (c) 2006 American Institute of Physics.