Suchergebnisse

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 2018e44 and under Elkartek RTM 4.0 projects, by Russian Foundation for Basic Research (Grant 16-53-48012) and partially supported by Act 211 Government of the Russian Federation, contract # 02. A03.21.0011. The authors thank for technical and human support provided by SGIker of UPV/EHU and European funding (ERDF and ESF). The work was carried out with financial support from the Ministry of Education and Science of the Russian Federation in the framework of increase Competitiveness Program of NUST "MISIS", implemented by a governmental decree dated 16th of March 2013, No 211.

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)

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.

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

Giant magnetoimpedance (GMI) effect is a powerful technique for magnetic label detection. Co-based amorphous ribbons are cheap materials showing high GMI effect at low operation frequencies for close to zero magnitostriction compositions. In this work magnetic properties and GMI were studied for CoFeMoSiB amorphous ribbons in as-quenched and surface modified states without and in the presence of water-based ferrofluid with electrostatic stabilization of γ-Fe2O3 nanoparticles. Surface modification by ultrasound treatment resulted in appearance of round defects with average diameter of about 150 micrometers. The GMI difference for as-quenched ribbons in absence and in the presence of ferrofluid was measured for the frequency range of 0.5 to 10 MHz. Although proposed surface modification by the ultrasound treatment did not improve the sensitivity limit for ferrofluid detection, it did not decrease it either. Observed changes of GMI are useful for understanding of functionality of GMI biosensors. © 2018 The Authors, published by EDP Sciences. ; The work was supported in part by the Government of the B is acknowledged for financial support under th e Elkartek Program, the Project Micro4Fab (KK -206/01 30)00 and the Ministry of dE ucation and Science of the RF Project N 055 , within the state job 3.21.61 20/17.9 . We thank I.V. Beketov , A.I . Medvedev and A. Larr anga for special support. Selected measurements were made at SGIKER services of .UPV/EHU

In this work a sensitive micrometric non-contact position sensor based on the Giant MagnetoImpedance effect (GMI) is analyzed. A nearly zero magnetostrictive CoFeSiBCr wire was employed as sensor nucleus. The sensing principle is based on the changes in the high frequency electric impedance, Z, of the soft magnetic element as a function of the relative position of a permanent magnet generating a non-uniform magnetic field along the wires axis. The sensor sensitivity is analyzed in terms of the magnetic field gradient and wire's length. The comparison between the sensing response of a single wire element and a long wire (12 cm in length) with different voltage contacts along its axis is performed. Higher micrometric sensitivities are achieved in wires with a certain critical length. A slight enhancement of the sensor sensitivity is found under the single wire configuration below the critical wire length. These results are interpreted as the contribution of the characteristic closure domain structure at the sample ends in these soft magnetic wires. Finally, the application of the sensor for the detection of the daily micrometric trunk shrinkage variations in a lemon tree is presented. The results indicate that this type of magnetic sensors can be easily implemented in the agricultural sector, providing a low cost and sensitive detection technique regarding water monitoring purposes. ; The work has been performed within the framework of the project VITICS, IIM14244.RI1 financially supported by the Departamento de Economía, Haciencia, Industria y Empleo, Navarra Government (Spain) and cofinanced with FEDER EU funds.

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).

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.

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).

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).

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).

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 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)