Giant magneto-impedance and magneto-inductive effects in amorphous alloys (invited)

Abstract

Recent experiments have discovered giant and sensitive magneto-impedance and magneto-inductive effects in FeCoSiB amorphous wires. These effects include a sensitive change in an ac wire voltage with the application of a small dc longitudinal magnetic field. At low frequencies (1–10 kHz) the inductive voltage drops by 50% for a field of 2 Oe (25%/Oe) reflecting a strong field dependence of the circumferential permeability. At higher frequencies (0.1–10 MHz) when the skin effect is essential, the amplitude of the total wire voltage decreases by 40%–60% for fields of 3–10 Oe (about 10%/Oe). These effects exhibit no hysteresis for the variation of an applied field and can be obtained even in wires of 1 mm length and a few micrometer diameter. These characteristics are very useful to constitute a highly sensitive microsensor head to detect local fields of the order of 10−5 Oe. In this paper, we review recently obtained experimental results on magneto-inductive and magneto-impedance effects and present a detailed discussion for their mechanism, developing a general approach in terms of ac complex impedance in a magnetic conductor. In the case of a strong skin effect the total wire impedance depends on the circumferential permeability through the penetration depth, resulting in the giant magneto-impedance effect.

Giant Magnetoimpedance in Ti/CoP Plated Wires

“…Similar peak phenomenon was observed in the uniform wires, ribbons and films, which was attributed to the existence of circumferential or transverse anisotropy and the permeability peak around anisotropy field H K (H K % H P ). [3][4][5][6][7][8] It has been found that in the electrodeposited CoP film there is a transition of magnetic anisotropy with regards to the thickness D of CoP: For D < 0:4 mm, the anisotropy is planar. For 0:4 mm < D < 10 mm it is an oblique anisotropy.…”

“…1,2) The GMI effect consists in a magnetic field induced changes in the complex impedance due to the variation of magnetic permeability. Besides of the uniform wires, ribbons and films, [3][4][5][6][7][8] this effect has been observed in inhomogeneous structured materials such as non -magnetic conducting wire plated with magnetic layers and some sandwich films. [9][10][11][12][13][14][15][16][17][18] Large GMI effect occurs at a relative low frequency in BeCu/NiFe, 9) BeCu/CoFeNi, 10) Ag/NiFe 11) and Cu/CoP 12,13) plated wires.…”

Enhancement of Magnetoimpedance in Fe<SUB>74.5&minus;<i>x</i></SUB>Cu<SUB><i>x</i></SUB>Nb<SUB>3</SUB>Si<SUB>13.5</SUB>B<SUB>9</SUB> As Cast Ribbons

“…[1][2][3][4][5][6][7][8][9][10][11] This effect includes a sensitive change in impedance with application of a small dc magnetic field. It has been widely accepted that the magnetoimpedance is strongly correlated with the variation of the penetration depth via the permeability.…”

Domain Transformation and MI of Melt-extracted Co68.15Fe4.35Si12.25B13.25Nb1Cu1 Microwires by Cryogenic Joule Annealing

“…The giant magneto-impedance (GMI) effect of these wires which used for weak-field detection and high-resolution sensors has been attracted much attentions [1][2][3] . Many previous works focused on annealing treatment for improving the GMI ratio and field response sensitivity of the microwires simultaneously by releasing the residual inner stress of an as-quenched microwire which enhances the circumferential permeability μ φ , such as joule heat-treatment and stress annealing [4][5][6][7][8] .…”