Studies of magnetic properties and GMI effect of amorphous Co-Fe rich microwires reveal that they present GMI effect at GHz frequencies. Magnetic field dependences of GMI effect are affected by the post-processing conditions. In particular, we observed that in Co-Fe rich microwires stress-annealing allows improvement of frequency dependence of GMI ratio at high frequencies. We discussed observed experimental dependences considering both different magnetic structure and the anisotropy in the bulk and near the surface and close analogy between giant magnetoimpedance and ferromagnetic resonance. ; This work was supported by Spanish MCIU under PGC2018-099530-B-C31 (MCIU/AEI/FEDER, UE), by the Government of the Basque Country under PIBA 2018-44 and Elkartek (RTM 4.0) projects and by the University of Basque Country under the scheme of "Ayuda a Grupos Consolidados" (Ref.: GIU18/192). The authors thank for technical and human support provided by SGIker of UPV/EHU (Medidas Magnéticas Gipuzkoa) and European funding (ERDF and ESF)
Thin magnetic wires can present excellent soft magnetic properties (with coercivities up to 4 A/m), Giant Magneto-impedance effect, GMI, or rectangular hysteresis loops combined with quite fast domain wall, DW, propagation. In this paper we overview the magnetic properties of thin magnetic wires and post-processing allowing optimization of their magnetic properties for magnetic sensor applications. We concluded that the GMI effect, magnetic softness or DW dynamics of microwires can be tailored by controlling the magnetoelastic anisotropy of as-prepared microwires or controlling their internal stresses and domain structure by appropriate thermal treatment. ; This work was funded by Spanish MCIU under PGC2018-099530-B-C31 (MCIU/AEI/FEDER, UE) by the Government of the Basque Country under PIBA 2018-44 projectand by the University of Basque Country under the scheme of "Ayuda a Grupos Consolidados" (Ref.: GIU18/192).
Herein, detailed studies on the influence of stress annealing on the magnetic softness and giant magnetoimpedance (GMI) ratio of Co69.2Fe3.6Ni1B12.5Si11Mo1.5C1.2 glass-coated microwires are provided. As-prepared microwire presents linear hysteresis loops, moderate GMI ratio with double-peak magnetic field dependence and low coercivity (4 A m−1), typically observed for wires with transverse magnetic anisotropy. However, after conventional annealing magnetic hardening and transformation of linear hysteresis loop into rectangular with coercivity about 90 A m−1 is surprisingly observed. It is shown that stress annealing allows preventing magnetic hardening and remarkably improving GMI ratio. Properly stress-annealed samples present better magnetic softness: almost unhysteretic loops with coercivity about 2 A m−1 and magnetic anisotropy field about 35 A m−1. Observed stress-annealing-induced anisotropy is affected by the tensile stresses, applied during annealing and by the annealing temperature. From the frequency dependence of the maximum GMI ratio, the optimum frequency ranges for as-prepared and stress-annealed samples are determined. The observed stress-annealing-induced magnetic anisotropy and associated changes in magnetic properties and GMI effect are discussed in terms of internal stresses relaxation and related modification of the magnetostriction coefficient, "back stresses," structural anisotropy, redistribution of internal stresses, and change of spatial distribution of magnetic anisotropy. ; This work was supported by the Spanish MCIU, under PGC2018-099530-B-C31 (MCIU/AEI/FEDER, UE), and by the Government of the Basque Country, under PIBA 2018-44 and Elkartek (CEMAP and AVANSITE) projects, and by the University of Basque Country, under the scheme of "Ayuda a Grupos Consolidados" (Ref.: GIU18/192) and COLAB20/15 project. The authors are thankful for the technical and human support provided by SGIker of UPV/EHU (Medidas Magnéticas Gipuzkoa) and European funding (ERDF and ESF).
There is a pressing demand to improve the performance of cost-effective soft magnetic materials for use in high performance sensors and devices. Giant Magneto-impedance effect (GMI), or fast single domain wall (DW) propagation can be observed in properly processed magnetic microwires. In this paper we have identified the routes to obtain microwires with unique combination of magnetic properties allowing observation of fast and single DW propagation and GMI effect in the same microwire. By modifying the annealing conditions, we have found the appropriate regimes allowing achievement of the highest GMI ratio and the fastest DW dynamics. The observed experimental results are discussed considering the radial distribution of magnetic anisotropy and the correlation of GMI effect, and DW dynamics with bulk and surface magnetization processes. Studies of both Fe- and Co-rich microwires, using the magneto-optical Kerr effect, MOKE, provide information on the magnetic structure in the outer shell of microwires. We have demonstrated the existence of the spiral helical structure in both studied microwires. At the same time, torsion mechanical stresses induce helical bistability in the same microwires, which allow us to consider these microwires as materials suitable for sensors based on the large Barkhausen jump. ; This work was funded by Spanish MCIU under PGC2018-099530-B-C31 (MCIU/AEI/FEDER, UE) by the Government of the Basque Country under PIBA 2018-44 project and Elkartek (CEMAP and AVANSITE) projects and by the University of Basque Country under the scheme of "Ayuda a Grupos Consolidados" (Ref.: GIU18/192).
The influence of post-processing conditions on the magnetic properties of amorphous and nanocrystalline microwires has been thoroughly analyzed, paying attention to the influence of magnetoelastic, induced and magnetocrystalline anisotropies on the hysteresis loops of Fe-, Ni-, and Co-rich microwires. We showed that magnetic properties of glass-coated microwires can be tuned by the selection of appropriate chemical composition and geometry in as-prepared state or further considerably modified by appropriate post-processing, which consists of either annealing or glass-coated removal. Furthermore, stress-annealing or Joule heating can further effectively modify the magnetic properties of amorphous magnetic microwires owing to induced magnetic anisotropy. Devitrification of microwires can be useful for either magnetic softening or magnetic hardening of the microwires. Depending on the chemical composition of the metallic nucleus and on structural features (grain size, precipitating phases), nanocrystalline microwires can exhibit either soft magnetic properties or semi-hard magnetic properties. We demonstrated that the microwires with coercivities from 1 A/m to 40 kA/m can be prepared. ; This research was funded by Spanish MCIU under PGC2018-099530-B-C31 (MCIU/AEI/FEDER, UE), by the Government of the Basque Country under PIBA 2018-44 and Elkartek (CEMAP and AVANSITE) projects and by the University of Basque Country under the scheme of "Ayuda a Grupos Consolidados" (Ref.: GIU18/192).
This work was supported by Spanish Ministry of Economy and Competitiveness (MINECO) under Projects MAT2013-47231-C2-1-P and MAT2013-47231-C2-2-P. VZ and AZ wish to acknowledge the support under Program of Mobility of the Researchers of the Basque Government (grants MV-2016-1-0025 and MV-2016-1-0018 respectively).
The influence of magnetic anisotropy, post-processing conditions, and defects on the domain wall (DW) dynamics of amorphous and nanocrystalline Fe-, Ni-, and Co-rich microwires with spontaneous and annealing-induced magnetic bistability has been thoroughly analyzed, with an emphasis placed on the influence of magnetoelastic, induced and magnetocrystalline anisotropies. Minimizing magnetoelastic anisotropy, either by the selection of a chemical composition with a low magnetostriction coefficient or by heat treatment, is an appropriate route for DW dynamics optimization in magnetic microwires. Stress-annealing allows further improvement of DW velocity and hence is a promising method for optimization of DW dynamics in magnetic microwires. The origin of current-driven DW propagation in annealing-induced magnetic bistability is attributed to magnetostatic interaction of outer domain shell with transverse magnetization orientation and inner axially magnetized core. The beneficial influence of the stress-annealing on DW dynamics has been explained considering that it allows increasing of the volume of outer domain shell with transverse magnetization orientation at the expense of decreasing the radius of inner axially magnetized core. Such transverse magnetic anisotropy can similarly a ect the DW dynamics as the applied transverse magnetic field and hence is beneficial for DW dynamics optimization. Stress-annealing allows designing the magnetic anisotropy distribution more favorable for the DW dynamics improvement. Results on DW dynamics in various families of nanocrystalline microwires are provided. The role of saturation magnetization on DW mobility improvement is discussed. The DW shape, its correlation with the magnetic anisotropy constant and the microwire diameter, as well as manipulation of the DW shape by induced magnetic anisotropy are discussed. The engineering of DW propagation through local stress-annealing and DW collision is demonstrated. ; This research was funded by Spanish MCIU under PGC2018-099530-B-C31 (MCIU/AEI/FEDER, UE), by the Government of the Basque Country under PIBA 2018-44 and Elkartek (CEMAP and AVANSITE) projects, and by the University of Basque Country under the scheme of "Ayuda a Grupos Consolidados" (Ref.: GIU18/192). J.O. wishes to acknowledge the support of the Ministry of Higher Education, Science and Technology of the Dominican Republic (2015 FONDOCyT program).
Amorphous soft magnetic microwires have attracted much attention in the area of sensor applications due to their excellent properties. In this work, we study the influence of annealing treatments (stress and conventional) in the giant magnetoimpedance (GMI) response and the field sensitivity of the soft magnetic Co69.2Fe3.6Ni1B12.5Si11Mo1.5C1.2 glass-coated microwires. Here we report a remarkable and simultaneous enhancement of GMI effect and field sensitivity. The highest sensitivity of 104%/Oe and the GMI response of 234% were achieved for 300 °C stress-annealed samples at 472 and 236 MPa, respectively. Additionally, we found that stress-annealed microwires exhibit a frequency dependence on maximal GMI response and field sensitivity. These findings are obtained by fine-tuning their magnetoeslastic anisotropies through stress-annealing treatments of as-prepared microwires at the proper temperature and axial applied stress upon annealing. We hope that the results presented here widen the scope of investigations for the future design of soft magnetic materials for sensor purposes. ; D.G.-A is founded by MAT2017-83631-C3-R. This work was also supported by Spanish MCIU under PGC2018-099530-B-C31 (MCIU/AEI/FEDER, UE) and by the Government of the Basque Country under PIBA 2018-44 project and by the University of Basque Country under the scheme of "Ayuda a Grupos Consolidados" (Ref.: GIU18/192).
Magnetic microwires can present excellent soft magnetic properties and a giant magnetoimpedance effect. In this paper, we present our last results on the effect of postprocessing allowing optimization of the magnetoimpedance effect in Co-rich microwires suitable for magnetic microsensor applications. Giant magnetoimpedance effect improvement was achieved either by annealing or stress-annealing. Annealed Co-rich presents rectangular hysteresis loops. However, an improvement in magnetoimpedance ratio is observed at fairly high annealing temperatures over a wide frequency range. Application of stress during annealing at moderate values of annealing temperatures and stress allows for a remarkable decrease in coercivity and increase in squareness ratio and further giant magnetoimpedance effect improvement. Stress-annealing, carried out at sufficiently high temperatures and/or stress allowed induction of transverse magnetic anisotropy, as well as magnetoimpedance effect improvement. Enhanced magnetoimpedance ratio values for annealed and stress-annealed samples and frequency dependence of the magnetoimpedance are discussed in terms of the radial distribution of the magnetic anisotropy. Accordingly, we demonstrated that the giant magnetoimpedance effect of Co-rich microwires can be tailored by controlling the magnetic anisotropy of Co-rich microwires, using appropriate thermal treatment. ; This work was supported by Spanish MCIU under PGC2018-099530-B-C31 (MCIU/AEI/FEDER, UE) and by the Government of the Basque Country under PIBA 2018-44 projects.
This work was supported by EU ERA-NET programme under Project "SoMaMicSens" (MANUNET 2010-Basque-3), by EU under FP7 "EM-safety" project and by the Basque Government under Saiotek 11 MICMAGN Project (S- PE11UN087). B.H. and L.G.-L. acknowledge the financial support from the Principado de Asturias (SV-PA-13- ECOEMP- 47), and L.G.-L. acknowledges a FPI grant of MICINN. Technical and human support provided by SGIker(UPV/EHU, MICINN, GV/EJ, ERDF, and ESF) is gratefully acknowledged
We overviewed the correlation between the structure, magnetic and transport properties of magnetic microwires prepared by the Taylor-Ulitovsky method involving rapid quenching from the melt and drawing of the composite (metallic core, glass coated) wire. We showed that this method can be useful for the preparation of different families of magnetic microwires: soft magnetic microwires displaying Giant magnetoimpedance (GMI) effect, semi-hard magnetic microwires, microwires with granular structure exhibiting Giant Magnetoresistance (GMR) effect and Heusler-type microwires. Magnetic and transport properties of magnetic microwires depend on the chemical composition of metallic nucleus and on the structural features (grain size, precipitating phases) of prepared microwires. In all families of crystalline microwires, their structure, magnetic and transport properties are affected by internal stresses induced by the glass coating, depending on the quenching rate. Therefore, properties of glass-coated microwires are considerably different from conventional bulk crystalline alloys. ; This work was supported by Spanish Ministry of Economy and Competitiveness (MINECO) under Projects MAT2013-47231-C2-1-P and MAT2013-47231-C2-2-P. The authors thank for technical and human support provided by SGIker (Magnetic Measurements Gipuzkoa) of UPV/EHU. VZ and AZ wish to acknowledge the support under Program of Mobility of the Researchers of the Basque Government (grants MV-2016-1-0025 and MV-2016-1-0018 respectively).
We studied magnetic properties and GMI effect of Finemet-type FeCuNbSiB microwires. We observed that GMI effect and magnetic softness of microwires produced by the Taylor-Ulitovski technique, can be tailored by either controlling magnetoelastic anisotropy of as-prepared FeCuNbSiB microwires or controlling their structure by heat treatment or changing the fabrication conditions. GMI effect has been observed in as-prepared Fe-rich microwires with nanocrystalline structure. ; This work was supported by EU ERA-NET programme under project "SoMaMicSens" (MANUNET-2010-Basque-3), by Spanish MICINN under project MAT2010-18914, by the Basque Government under Saiotek-12 MEMFOMAG project (S-PE12UN139) and by federal target program "Scientific and scientific-pedagogical personnel of innovative Russia", state contract no 14.R18.21.0762. A. Zh. and V.Zh. wish to acknowledge support of the Basque Government under the Mobility Program (grants MV-2013-2-22 and MV-2013-2-23). Technical and human support provided by SGIker (UPV/EHU, MICINN, GV/EJ, ERDF and ESF) is gratefully acknowledged.
