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Optimization of Giant Magnetoimpedance Effect of Amorphous Microwires by Postprocessing

Published version
Peer-reviewed

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Abstract

jats:pMagnetic microwires with amorphous structures can present a unique combination of excellent magnetic softness and giant magnetoimpedance (GMI) effects together with reduced dimensions and good mechanical properties. Such unique properties make them suitable for various technological applications. The high GMI effect, observed in as-prepared Co-rich microwires, can be further optimized by postprocessing. However, unexpected magnetic hardening and a transformation of the linear hysteresis loop into a rectangular loop with a coercivity on the order of 90 A/m were observed in several Co-rich microwires upon conventional annealing. Several routes to improve magnetic softness and GMI effect in Fe- and Co-rich magnetic microwires are provided. We observed that stress annealing could remarkably improve the magnetic softness and GMI ratio of Co-rich microwires. Thus, almost unhysteretic loops with a coercivity of 2 A/m and a magnetic anisotropy field of about 70 A/m are achieved in Co-rich microwires stress annealed at appropriate conditions. The observed change in hysteresis loops and the GMI effect is explained by stress-annealing-induced anisotropy, which is affected by the stresses applied during annealing and by the annealing temperature. While as-prepared Fe-rich amorphous microwires present a low GMI effect, appropriate postprocessing (annealing and stress annealing) allows for a remarkable GMI ratio improvement (an order of magnitude). The evaluated dependence of the maximum GMI ratio on frequency allows the identification of the optimal frequency band for the studied samples. The origin of stress-annealing-induced anisotropy and related changes in hysteresis loops and the GMI effect are discussed in terms of the relaxation of internal stresses, “back-stresses”, as well as structural anisotropy.</jats:p>

Description

Peer reviewed: True


Acknowledgements: The authors are thankful for the technical and human support provided by SGIker of UPV/EHU (Medidas Magneticas Gipuzkoa) and European funding (ERDF and ESF). We wish to thank the administration of the University of the Basque Country, which not only provides very limited funding but even expropriates the resources received by the research group from private companies for the research activities of the group. Such interference helps keep us on our toes.


Publication status: Published

Keywords

4004 Chemical Engineering, 40 Engineering

Journal Title

Processes

Conference Name

Journal ISSN

2227-9717
2227-9717

Volume Title

12

Publisher

MDPI AG
Sponsorship
EU (HORIZON-CL5-2021-D5-01-06, HORIZON-CL4-2023-RESILIENCE-01)
Spanish MICIN (PID2022-141373NB-I00)
Government of the Basque Country (IT1670-22)