Magnetotransport at High Frequency of Soft Magnetic Amorphous Ribbons

Abstract

Abstract. Magnetic properties of amorphous alloy ribbons have been extensively studied for nearly a quarter of a century since their first production. Much interest in these materials has been stimulated by their remarkable magnetomechanical and magnetotransport properties. It is amazing to notice with respect to the so-called giant magnetoimpedance effect (GMI) effect that the rapid advantages in the understanding of the underlying physical mechanisms of GMI have allowed the development of practical devices and applications using this effect. Therefore, the large influence of magnetic fields and also mechanical stresses in determining the magnetic permeability and electrical impedance of such soft ferromagnetic alloys make these materials very suitable for sensing magnetic field, current and stress. In this chapter we will try to report the recent studies on GMI response of near-zero magnetostriction Co-based amorphous ribbons in as-cast (with different wide dimension) state, and exhibiting a macroscopic uniaxial magnetic anisotropy induced by different stressannealing treatment (300 MPa applied tensile stress at different temperature i.e., 340, 360, and 400 ºC, during 1 h) in the frequency range from 10 MHz up to 1000 MHz. Comparison among GMI effect of as-cast state and stress-annealed ribbons will be discussed. It is remarkable that a more spectacular and defined GMI effect is observed in the stress-annealed ribbons owing to the presence of a macroscopic uniaxial transverse magnetic anisotropy developed with the stressannealing treatment that enhances the transverse component of the magnetic susceptibility.

Novel Giant Magnetoimpedance Magnetic Field Sensor

“…One of the effects with great potential in sensor application is the phenomenon of giant magnetoimpedance (GMI). The GMI phenomenon consists of a significant (gigantic) change in the impedance of the high-frequency ferromagnetic AC conductor in the presence of a constant magnetic field [12]. The impedance changes reach several hundred % [13], while the sensitivity reaches 1.5%/A/m [14].…”