Magneto-impedance of glass-coated Fe-Ni-Cu microwires

TL;DR

This study investigates the magneto-impedance behavior of glass-coated Fe-Ni-Cu microwires across a range of RF frequencies, revealing a frequency-dependent crossover from negative to positive MI linked to skin depth and potential GMR effects.

Contribution

It provides new insights into the frequency-dependent MI response of Fe-Ni-Cu microwires and suggests possible GMR influence on their magnetic properties.

Findings

Negative MI at low frequencies (<20 MHz) with a peak at zero field.

Crossover to positive MI at higher frequencies.

Large saturation fields indicating GMR influence.

Abstract

The magneto-impedance (MI) of glass-coated Fe-Ni-Cu microwires was investigated for longitudinal radio-frequency (RF) currents up to a frequency of 200 MHz using an RF lock-in amplifier method. The MI, defined as DZ/Z = [Z(H)-Z(H=0.3T)]/Z(H=0.3T), displays a peak structure (negative MI) at zero field for RF currents with frequencies less than 20MHz and this crosses over to a sharp dip (positive MI) at higher frequencies. This crossover behavior is ascribed to the skin-depth-limited response primarily governed by the field-dependence of the permeability. Large saturation fields (300 to 600 Oe) and other anomalies indicate the possible influence of giant magneto-resistance (GMR) on the MI.