Enhanced giant magnetoimpedance effect and field sensitivity in Co-coated soft ferromagnetic amorphous ribbons

Nicholas Laurita,Christopher Bauer,Alex Leary,Casey Miller,Michael E Mchenry,Priyanga Jayathilaka,Hariharan Srikanth,Anurag Chaturvedi,Manh-Huong Phan

doi:10.1063/1.3548857

Nicholas Laurita, Christopher Bauer + Show 7 more

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https://doi.org/10.1063/1.3548857

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Abstract

A 50 nm-thick Co film has been grown either on the free surface (surface roughness, ∼6 nm) or on the wheel-side surface (surface roughness, ∼147 nm) of Co84.55Fe4.45Zr7B4 amorphous ribbons. A comparative study of the giant magnetoimpedance (GMI) effect and its field sensitivity (η) in the uncoated and Co-coated ribbons is presented. We show that the presence of the Co coating layer enhances both the GMI ratio and η in the Co-coated ribbons. Larger values for GMI ratio and η are achieved in the sample with Co coated on the free ribbon surface. The enhancement of the GMI effect in the Co-coated ribbons originates mainly from the reduction in stray fields due to surface irregularities and the enhanced magnetic flux paths closure. These findings provide good guidance for tailoring GMI in surface-modified soft ferromagnetic ribbons for use in highly sensitive magnetic sensors.

Highlights

(GMI) effect in soft ferromagnetic ribbons makes them attractive for magnetic sensor applications.1,2 giant magnetoimpedance (GMI) is a large change in the ac impedance of a ferromagnetic conductor subject to a dc magnetic field.1 The impedance (Z) of a ferromagnetic ribbon can be calculated by3
We report here a comparative study of the GMI effect and its field sensitivity (g) in Co84.55Fe4.45Zr7B4 amorphous ribbons with and without 50 nm thick Co layers deposited on either the free ribbon surface or on the wheel-side ribbon surface
It is shown that the presence of the Co coating layer reduces stray fields due to surface irregularities, and closes up the magnetic flux path, both of which contribute to the enhanced GMI effect in the Co-coated ribbons

Summary

Introduction

(GMI) effect in soft ferromagnetic ribbons makes them attractive for magnetic sensor applications.1,2 GMI is a large change in the ac impedance of a ferromagnetic conductor subject to a dc magnetic field.1 The impedance (Z) of a ferromagnetic ribbon can be calculated by3. We report here a comparative study of the GMI effect and its field sensitivity (g) in Co84.55Fe4.45Zr7B4 amorphous ribbons with and without 50 nm thick Co layers deposited on either the free ribbon surface (surface roughness, $6 nm) or on the wheel-side ribbon surface (surface roughness, $147 nm).

Results

Conclusion