High-frequency magneto-impedance in metastable metallic materials: An overview

The giant magneto-impedance effect (GMI) is a common feature of a wide class of metastable ferromagnetic alloys. This effect can be enhanced by submitting the as-prepared materials to suitable thermal treatments. Recently, a remarkably high magneto-impedance response has been observed in the GHz region for several systems. The increase in miniaturization of telecommunication devices dramatically increases the working frequencies; as a consequence, the interest in studying magneto-impedance effect leads to microwave region.In this paper, analogies and differences among the magneto-transport effect observed in ferromagnetic metastable alloys will be highlighted and discussed from the experimental point of view in a wide range of frequencies.