Author/Authors :
Guo، نويسنده , , H.Q. and Chen، نويسنده , , C. and Li، نويسنده , , M. and Zhao، نويسنده , , T.Y. and Luan، نويسنده , , K.Z. and Shen، نويسنده , , B.G. and Liu، نويسنده , , Y.H. and Zhao، نويسنده , , J.G. and Mei، نويسنده , , L.M. and Kronmüller، نويسنده , , H.، نويسنده ,
Abstract :
The magnetoimpedance spectra (0 ≤ f ≤ 3 MHz) of amorphous and of nanocrystallized (550 °C annealing for 0.5–18 h) FeCuNbSiB ribbons were measured at room temperature using a commercial impedance analyzer as a function of applied magnetic field up to 75 Oe. The magnetoimpedance (MI), Z(f, H), shows strong dependence on frequency of the drive, ac current and magnetic field. For all the samples, the MI ratio ΔZ/Z = (Z(Hmax) − Z(0))/Z(Hmax) first increases rapidly with frequency (f) and reaches a maximum at about 300–500 kHz, then decreases with Ff. The maximum value of the MI ratio ΔZ/Z, −227%, is obtained in the sample annealed at 550 °C for 3 h with ac current at 300 kHz. At higher frequency, a peak in field dependence of the MI ratio (Z(H) − Z(0))/Z(Hmax) was obtained for nanocrystalline samples, but not for as-quenched amorphous connterparts. The field dependence of effective permeability has been shown to be responsible for their MI effects.
