Analysis of thin-film magnetoimpedance behavior in low MHz regions based on domain wall equation and bias susceptibility theory

Hiroaki Kikuchi,Shuichiro Hashi,Shin Yabukami,Chihiro Sumida,Hiroaki Uetake,Kazushi Ishiyama

doi:10.1063/1.4973760

Hiroaki Kikuchi, Shuichiro Hashi + Show 4 more

Open Access

https://doi.org/10.1063/1.4973760

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Abstract

An interesting behavior of thin-film magnetoimpedance elements in the relatively low megahertz (MHz) region is found experimentally when the width of the element is narrow and the thickness of elements is several micrometers. The impedance peaks and inductance shows a rapid drop at around 10 MHz when a bias field is applied to such elements. The impedance profiles of the elements were analyzed on the basis of a domain wall motion equation and bias susceptibility theory. Calculation of the domain wall motion equation when accounting for domain resonance explains the impedance behavior in the low MHz region. The rapid drop in inductance and peak in impedance can be attributed to the domain wall resonance. At a relatively higher frequency, above 100 MHz, the calculation of bias susceptibility while considering ferromagnetic resonance thoroughly explains the experimental behavior.

Highlights

Magnetoimpedance (MI), the exhibition of a large change in the impedance of conductive soft magnetic materials when subjected to a magnetic field,[1] has been attracted to the higher sensitivity of such materials as compared to other types of magnetic sensors.[2,3] Though amorphous wires and ribbons are mainly used,[4,5,6,7] an added advantage of the thin-film MI sensor geometry is compatibility of the elements with miniaturized integrated electronic devices
Thin-film MI elements with a thickness of several microns operate at frequencies above 100 MHz due to limitations imposed by the skin effect and ferromagnetic resonance (FMR),[8,9,10] making such elements unsuitable for drive and detection circuits, which normally operate below the dozens of megahertz (MHz) region
The impedance peaks at 10 MHz with a bias field of 6.5 Oe were accompanied by a drastic decrease in inductance

Summary

INTRODUCTION

Magnetoimpedance (MI), the exhibition of a large change in the impedance of conductive soft magnetic materials when subjected to a magnetic field,[1] has been attracted to the higher sensitivity of such materials as compared to other types of magnetic sensors.[2,3] Though amorphous wires and ribbons are mainly used,[4,5,6,7] an added advantage of the thin-film MI sensor geometry is compatibility of the elements with miniaturized integrated electronic devices. Thin-film MI elements with a thickness of several microns operate at frequencies above 100 MHz due to limitations imposed by the skin effect and ferromagnetic resonance (FMR),[8,9,10] making such elements unsuitable for drive and detection circuits, which normally operate below the dozens of megahertz (MHz) region. Contrary to these common conventions, we experimentally observed an interesting behavior of thin-film MI elements in the relatively lower MHz region:[11] a peak in impedance and rapid drop in inductance against frequency when a bias field is applied. We analyzed the impedance profiles of such elements under bias on the basis of a domain wall motion equation[12] and the bias susceptibility theory.[13,14]

EXPERIMENTAL AND IMPEDANCE THEORY

Domain wall equation

Bias susceptibility

RESULTS AND DISCUSSION

CONCLUSION