AN ALTERNATIVE APPROACH TO GIANT MAGNETOIMPEDANCE PHENOMENA IN AMORPHOUS FERROMAGNETIC WIRES

Magnetoimpedance in as-cast, nonmagnetostrictive CoFeBSi amorphous ferromagnetic wires, submitted to an ac electric current of 5 mA in the frequency range 100 Hz-100 kHz, is analyzed in terms of equivalent circuits. It is shown that the equivalent circuit representing the wire frequency behavior can he approximated by a parallel L(p)R(p) arrangement with elements R(s) and L(s) in series; L(p) and R(p) are associated with circumferential domain wall permeability and wall damping, respectively; L(s) is related to the circumferential rotational permeability of the wire, and R(s) accounts for the de resistance in the circuit. When the wire is submitted to a longitudinal de field high enough to approach saturation (H-dc=3600 A/m), the circuit becomes simply a series R(s)L(s) circuit. The various contributions from basic magnetization processes to magnetoimpedance are discussed, as well as deviations from this idealized model. (C) 1995 American Institute of Physics.