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

Dawei Xing,Jianfei Sun,Lunyong Zhang,Dongming Chen,Jingshun Liu,Fang Liu,Hongexian Shen

doi:10.1590/1516-1439.327914

Abstract

Giant magneto-impedance (GMI) effect and domain transformation for melt-extracted Co68.15Fe4.35Si12.25B13.25Nb1Cu1 amorphous wires have been induced by a cryogenic Joule annealing (CJA) treatment with different DC current amplitude (0~350 mA) for 240s. Experimental results indicate that the maximum GMI ratio ([ΔΖ∕Ζ0]max) achieves to 188.1% with exciting field increasing to 1.8 Oe monotonically for 300 mA annealing treated wires, which can attribute to the surface complex domain structure change formed by CJA treatment. The liquid nitrogen can protect the wire from crystallization when applied large DC currents. Moreover, the CJA treatment can improve the response sensitivities effectively. These remarkable characteristics make the melt-extracted microwires by CJA tailoring as the promising candidate material for small-sized magnetic sensors.

Highlights

The ferromagnetic microwires have been recognized as promising materials for small-size magnetic sensors in recent years
In the cryogenic Joule annealing (CJA) process, the microwire is surrounded by nitrogen gas
The nearly linear response field is enhanced to 1.8 Oe with the improving of the response sensitivity which is suitable for highly sensitive Giant magneto-impedance (GMI) sensors application

Summary

Introduction

The ferromagnetic microwires have been recognized as promising materials for small-size magnetic sensors in recent years. 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 μφ, such as joule heat‐treatment and stress annealing[4,5,6,7,8]. The complex impedance Z can be expressed as Z(H0)=R(H0)+iX(H0), where R(H0) and X(H0) are the resistance and the reactance at zero external field, respectively. In this case, the reducing R(H0) and X(H0) simultaneously is favor of obtaining high GMI performance

Methods

Results

Conclusion