Giant Magneto-impedance Effect in Nanocrystalline Fe_73.5CuNb₃Si_13.5B₉ Ribbons

Magneto-impedance (MI) effects have been observed in amorphous and nanocrystalline Fe_73.5CuNb₃Si_13.5B₉ ribbons. Large MI values have been obtained in nanocrystalline samples (NCS), but not in as-quenched samples (AQS). The magnetic responses of impedance of nanocrystalline samples share some common features with that of Co-based amorphous wire and ribbon samples. The field dependencies of effective permeability for nanocrystalline samples have shown a sharp change at the anisotropy field. The effective permeability and the hysteresis loops for AQS and NCS have been shown to be responsible for their MI effects. The sensitivity of the magnetic responses in the nanocrystalline sample can reach 50%/Oe.