Giant Magneto-impedance in stress-annealed Finemet/Copper/Finemet based trilayer structures

TL;DR

This study demonstrates giant magneto-impedance effects in stress-annealed Finemet/Copper/Finemet trilayers, with significant enhancements in MI ratios and sensitivities achieved through perpendicular bias fields, promising for magnetic sensing applications.

Contribution

It reports the first large MI ratios in Finemet-based trilayers and shows how perpendicular bias fields significantly enhance MI performance.

Findings

Maximum MI ratios of 700% (resistance) and 450% (inductance) in 30-600 kHz range.

MI ratio for resistance increases to 2500% with perpendicular bias fields.

Sensitivity improves from 48%/Oe to 288%/Oe at 600 kHz with bias fields.

Abstract

The resistive and reactive components of magneto-impedance (MI) for Finemet/Copper/Finemet sandwiched structures based on stress-annealed nanocrystalline Fe75Si15B6Cu1Nb3 ribbons as functions of different fields (longitudinal and perpendicular) and frequencies have been measured and analyzed. Maximum magneto-resistance and magneto-inductance ratios of 700% and 450% have been obtained in 30-600 kHz frequency range respectively. These large magneto-resistance and magneto-inductive ratios are a direct consequence of the large effective relative permeability due to the closed magnetic flux path in the trilayer structure. The influence of perpendicular bias fields (Hper) in the Longitudinal Magneto-impedance (LMI) configuration greatly improves the MI ratios and sensitivities. The maximum MI ratio for the resistive part increases to as large as 2500% for Hper ~ 1 Oe. The sensitivity of the magneto-resistance increases from 48%/Oe to 288%/Oe at 600 kHz frequency with the application of Hper ~ 30 Oe. Such high increase in MI ratios and sensitivities with perpendicular bias fields are due to the formation the favourable (transverse) domain structures.