Giant magnetoimpedance effect in Fe-Zr-Nb-Cu-B nanocrystalline ribbons

The giant magnetoimpedance effect of the nanocrystalline ribbon Fe84Zr2.08Nb1.92Cu1B11 (atom fraction in %) was investigated. There is an optimum annealing temperature (T-A approximate to 998 K) for obtaining the largest GMI (giant magnetoimpedance) effect in the ribbon Fe84Zr2.08Nb1.92Cu1Bi11. The ribbon with longer ribbon length has stronger GNU effect, which may be connected with the demagnetization effect of samples. The frequency f(max), where the maximum magnetoimpedance GMI(Z)(max) = [(Z(H) - Z(0))/Z(0)](max) occurs, is near the intersecting frequency f(i) of the curves of GMI(R), GMI(X), and GMI(Z) versus frequency. The magnetoreactance GMI(X) decreases monotonically with increasing frequency, which may be due to the decrease of permeability. In contrast, with the AC (alternating current) frequency increasing, the magnetoresistance GMI(R) increases at first, undergoes a peak, and under then drops. The increase of the magnetoresistance may result from the enhancement of the skin effect with frequency. The maximum magnetoimpedance value GMI(Z)(max) under H = 7.2 kA/m is about -56.18% at f = 0.3 MHz for the nanocrystalline ribbon Fe84Zr2.08Nb1.92Cu1B11 with the annealing temperature T-A = 998 K and the ribbon length L = 6 cm.