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 a rf lock-in amplifier method. The MI, defined as DZ/Z5@Z(H)2Z(H50.3 T!#/Z(H50.3 T), displays a peak structure ~negative MI! at zero field for rf currents with frequencies less than 20 MHz 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. © 2000 American Institute of Physics.
Wiggins, J.; Srikanth, H.; Wang, K.-Y.; Spinu, L.; and Tang, Jinke (2000). "Magneto-impedance of glass-coated Fe–Ni–Cu microwires." JOURNAL OF APPLIED PHYSICS 87.9, 4810-4812.