Amorphous Glass-coated Microwires Research Articles

Magnetic Properties and Applications of Glass-coated Ferromagnetic Microwires

A remarkable magnetic softness and giant magnetoimpedance (GMI) effect at GHz frequency range havebeen observed in glass-coated microwires subjected to appropriate postprocessing. Co-based microwires present higher GMI effect. Insulating and flexible glass-coating allows use of magnetically soft amorphous glass-coated microwires for stresses or temperature monitoring insmartcomposites using free space facility. Such composites with magnetic microwire inclusions can present tunable magnetic permittivity. We report on in-situ the evolution of the transmission and reflection parameters of the polymer containing magnetic microwire inclusions during the polymerization process. A remarkable change of the reflection and transmission in the range of 4-7 GHz upon the matrix polymerization is observed. Observed dependencies are discussed in terms of the effect of the temperature and stresses variation on magnetic properties of glass-coated microwires during the thermoset matrix polymerization. Obtained results are considered as a base for novel sensing technique allowing non-destructive and non-contact monitoring of the composites utilizing ferromagnetic glass-coated microwire inclusions with magnetic properties sensitive to tensile stress and temperature.

The Magnetostriction of Amorphous Magnetic Microwires: The Role of the Local Atomic Environment and Internal Stresses Relaxation

We studied the magnetostriction coefficients, λs, Curie temperature, Tc, and their dependence on annealing conditions in Fe47Ni27Si11B13C2 and Co67Fe3.9Ni1.5B11.5Si14.5Mo1.6 amorphous glass-coated microwires with rather different character of hysteresis loops. A positive λs ≈ 20 × 10−6 is observed in as-prepared Fe47Ni27Si11B13C2, while low and negative λs ≈ −0.3 × 10−6 is obtained for Co67Fe3.9Ni1.5B11.5Si14.5Mo1.6 microwire. Annealing affects the magnetostriction coefficients and Curie temperatures, Tc, of both Fe47Ni27Si11B13C2 and Co67Fe3.9Ni1.5B11.5Si14.5Mo1.6 glass-coated microwires in a similar way. Observed dependencies of hysteresis loops, λs and Tc on annealing conditions are discussed in terms of superposition of internal stresses relaxation and structural relaxation of studied microwires. We observed linear λs dependence on applied stress, σ, in both studied microwires. A decrease in the magnetostriction coefficient upon applied stress is observed for Co-rich microwires with low and negative magnetostriction coefficient. On the contrary, for Fe-Ni-rich microwires with a positive magnetostriction coefficient, an increase in the magnetostriction coefficient with applied stress is observed. The observed results are discussed considering the internal stresses relaxation and short range atomic rearrangements induced by annealing on hysteresis loops, magnetostriction coefficients and Curie temperatures of studied microwires.

MI-Sensor Element Features and Estimation of Penetration Depth and Magnetic Permeability by Magnetoresistance and Magnetoreactance of CoFeSiB Amorphous Wires

The magnetoimpedance (MI) of amorphous soft magnetic Co <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">68.15</sub> Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4.35</sub> Si <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12.5</sub> B <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">15</sub> wires produced by the in-rotating water quenching technique was systematically studied. The behavior of the MI-element designed for magnetic sensors was examined in an external longitudinal dc magnetic field in the low-frequency range (f ≤ 1 MHz) and at the beginning of the intermediate frequency range (2 MHz ≤ f ≤ 5 MHz). A critical frequency of about 5 kHz - 7 kHz was observed with an initial increase in the MI effect. A maximum MI ratio of 334% was recorded at 0.95 MHz in a magnetically saturated MI-element. The intermediate frequency range is explored using the magnetoresistive - MR and magnetoreactive - MX components of magnetoimpedance Z. The MI anisotropy field profile occurs in the MHz operating frequency range with values increasing up to 25 A/m, exhibiting frequency dependence. The magnetic penetration depth was calculated using experimental magnetoresistance data, and the values obtained were about 3 μm - 4 μm for 5 MHz, showing a saturation trend. The magnetic permeability is analyzed in the framework of the electromagnetic classical high-limit model of a cylinder, which includes penetration depth and magnetoreactance. In our experiments and calculations, the classical high limit is satisfied in the operating frequency range of a few MHz. The magnetic permeability peak value is about 35% lower than the comparable data of amorphous CoFeNiMoSiB glass-coated microwires.

Tuning the giant magnetoimpedance response of a glass-coated microwire reinforced polymer by in-situ laser annealing

The ability to modify the giant magnetoimpedance (GMI) effect in amorphous glass-coated ferromagnetic Co-based microwire reinforced polymer via laser irradiation is presented. Through in-situ laser annealing of microwires embedded into a polymer matrix, a 25 % improvement in the GMI response is demonstrated after only 4.9 min of annealing. This improvement is compared to a conventional oven anneal technique, requiring an hour of oven annealing, subsequent sample cooling and polymer casting. This unique in-situ technique offers a novel and expedient path toward tailorable multi-functional composites in the areas of tunable electromagnetic shielding, structurally integrated antennas and magnetic sensors.

Off-Diagonal Magnetoimpedance in Annealed Amorphous Microwires with Positive Magnetostriction: Effect of External Stresses

It was observed recently that the giant magnetoimpedance (GMI) effect in Fe-rich glass-coated amorphous microwires with positive magnetostriction can be improved significantly by means of post-annealing. The increase in the GMI is attributed to the induced helical magnetic anisotropy in the surface layer of the microwire, which appears after the annealing. The application of external stresses to the microwire may result in changes in its magnetic structure and affect the GMI response. In this work, we study theoretically the influence of the tensile and torsional stresses on the off-diagonal magnetoimpedance in annealed amorphous microwires with positive magnetostriction. The static magnetization distribution is analyzed in terms of the core–shell magnetic structure. The surface impedance tensor is obtained taking into account the magnetoelastic anisotropy induced by the external stresses. It is shown that the off-diagonal magnetoimpedance response exhibits strong sensitivity to the magnitude of the applied stress. The obtained results may be useful for sensor applications of amorphous microwires.

Magneto-optical imaging of the domain wall distortions enhanced by magnetic fields in amorphous glass-coated microwire

Here, we employ time-resolved magneto-optical Kerr system (MOKE) imaging to ascertain the origin of domain wall motion in microwires. The MOKE visualisations of the domain walls motion on the surface of the microwires prove the domain wall pinning and distortions tailored due to the perpendicular magnetic field. It is shown that domain wall pinning in a perpendicular field increases the domain wall tilting angle, which is in turn, related to the apparent domain wall velocity. The obtained result is important for correct interpretation of domain wall velocity measurements in microwires obtained by the Sixtus-Tonks method.

Temperature influence on magnetic properties and magnetoimpedance effect of Fe-rich glass-coated microwires

Giant magnetoimpedance, GMI, effect and magnetic properties upon temperature influence of as-prepared and stress-annealed amorphous Fe75B9Si12C4 glass-coated microwires produced by the Taylor-Ulitovsky technique are analyzed. Remarkable change in the hysteresis loops and GMI effect is observed for both samples upon heating. Tuning of the stress-annealing conditions allows one to vary the temperature dependence. Furthermore, it is observed almost complete reversibility of the changes induced by the temperature. Observed dependences are explained by the heating effect on the internal stresses relaxation, by the modification of the thermal expansion coefficients of the metallic nucleus and the glass coating, and by the Hopkinson effect.

High-Sensitivity Wireless Sensing Using Amorphous Magnetic Microwires

Glass-coated amorphous ferromagnetic microwires subjected to variations in mass loading and parallel wire arrays with 0.5–6-cm interwire spacing were found to deliver exceptional magnetomechanical and wireless giant magnetoimpedance (GMI) responses, in the kilohertz and microwave range, respectively. The microwires allow wireless quantification of microgram mass differences: the magnetomechanical resonance frequency measured in zero applied field demonstrates an approximately linear decrease of 3 Hz/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{g}$ </tex-math></inline-formula> , and a sensitivity response that is ten times greater than that reported for commercial METGLAS-type amorphous magnetic ribbons of comparable length. Microwave giant magnetoimpedance data collected from planar arrays of parallel microwires show either constructive or destructive interference when compared to data obtained from a single microwire. The exceptional responsiveness of the glass-coated amorphous ferromagnetic microwires to mass loading and to geometric arrangement, along with their small diameter and ease of fabrication, highlights their promise for a wide variety of sensor applications, including biosensing, civil infrastructure monitoring, and high-throughput remote detection schemes.

Ultralight broadband microwave-absorbing materials based on the short fibers of glass-coated amorphous magnetic microwires

Glass-coated amorphous magnetic microwires (GAWs) typically have a glass skin and amorphous metal alloy inner core, giving them special electromagnetic (EM) properties. GAWs not only exhibit multiple EM losses and suitable impedance matching but also have a conductive core with magnetic properties. In this study, GAW filament fibers (LFs) and short fibers (SFs) were prepared, and they exhibited completely different EM performance. LFs with filaments closely arrayed reflected EM waves and could thus act as an EM shielding material, whereas SFs with randomly distributed fibers demonstrated excellent microwave-absorbing (MA) properties. Single-layer SFs of just 3 g/m2 and a length of 5 mm had a minimum reflectivity (RL) of −20.4 dB at 12.3 GHz, and the effective absorption bandwidth (EAB) of RL< −10 dB was 5.36 GHz with a thickness of just 1 mm. Moreover, the MA properties of the SFs were obtained and controlled by adjusting the length, content, and lamination of the SFs in accordance with their multiple MA mechanisms. Double-layer SFs with a thickness of 2 mm could also achieve an EAB (RL< −10 dB) above 10 GHz. The novel and effective strategy proposed in this study can thus produce SFs GAWs from ultralight MA fabric that exhibit excellent MA properties and broadband.

Direct Visualization of a Domain Wall Pinning by Time-Resolved Microscopy in Amorphous Glass-Coated Microwires

Amorphous glass-coated microwires with positive magnetostriction are composite material with very fast domain wall (DW) propagation that can reach up to 18 km/s. Previously it was shown that such high DW velocity can be explained by the tilted orientation of a DW in static or quasi-static experimental conditions. Here we perform time-resolved observation of a DW in propagation. The shape of a DW is studied via magneto-optical Kerr effect (MOKE) imaging. Time-resolved MOKE microscope operating in the single-shot regime and a static mode is used to ascertain the role of surface pinning on DW velocity fluctuation. It is shown that a tilted DW undergoes complex DW distortions on a local scale.

Ultralight Broadband Microwave Absorbing Materials Basing on Short Fibers of the Glass-Coated Amorphous Magnetic Microwires

Ultralight Broadband Microwave Absorbing Materials Basing on Short Fibers of the Glass-Coated Amorphous Magnetic Microwires

Ultralight Broadband Microwave-Absorbing Materials Based on the Short Fibers of Glass-Coated Amorphous Magnetic Microwires

Ultralight Broadband Microwave-Absorbing Materials Based on the Short Fibers of Glass-Coated Amorphous Magnetic Microwires

Ultralight Broadband Microwave Absorbing Materials Basing on Short Fibers of the Glass-Coated Amorphous Magnetic Microwires

Ultralight Broadband Microwave Absorbing Materials Basing on Short Fibers of the Glass-Coated Amorphous Magnetic Microwires

Mechanical Properties Test and Simulation Analysis of Glass Coated Amorphous Filaments

Taking the Co68.7Fe4Ni1B13Si11Mo2.3 glass-coated amorphous microwire as the research object, the mechanical properties of the amorphous wire were tested through biaxial tensile experiments, and the fracture deformation process of the amorphous wire was analyzed. Based on the experimental data, the finite element method was used The simulation software ABAQUS numerically simulates the tensile deformation of the amorphous wire, and the fracture relationship between the glass cladding layer and the core wire, and further reveals the tensile deformation fracture behavior of the amorphous wire was analyzed. The experimental results indicate that the fabricated microwires exhibit good tensile properties, and the maximum tensile breaking strength can reach 2918MPa; the fracture of the amorphous wire is a typical brittle fracture, and there is no obvious yield phenomenon. The tensile mechanics simulation results of the amorphous wire are consistent with the experimental results. The glass cladding layer breaks before the core wire, and the stress transfer effect in the amorphous wire is good. The model fracture is consistent with the fracture morphology of the amorphous wire. These results show that the amorphous wire exhibits good tensile properties and stress transmission capabilities, confirming the huge application potential of amorphous wire materials in sensor applications and functional composite materials.

Influence of Joule heating on electrical resistivity in Co-rich amorphous microwires

The paper investigates the electrical resistivity of two types of the glass-coated Co-rich amorphous ferromagnetic microwires during the Joule heating by direct current. We measured the relationships between the microwire’s resistivity and the power, which applied to the samples in as-prepared and crystallized conditions. Both types of microwires were demonstrated to completely crystallize on exposure to a temperature of more than 600 °C. During heating by a power up to 2.5 W (~400 °C), the microwires with Mo-Ni content were characterized by a monotonic resistivity increase with the temperature. But the microwires with Cr content had a well-marked resistivity minimum near the temperature Tм ~ 163 °C. This minimum shifted to a temperature value of ~260 °C after annealing. The research shows that the temperature dependence of resistivity in the temperature range below Tм obeys the f(T) = -ln(T) law.

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The paper investigates the electrical resistivity of two types of the glass-coated Co-rich amorphous ferromagnetic microwires during the Joule heating by direct current. We measured the relationships between the microwire’s resistivity and the power, which applied to the samples in as-prepared and crystallized conditions. Both types of microwires were demonstrated to completely crystallize on exposure to a temperature of more than 600 °C. During heating by a power up to 2.5 W (~400 °C), the microwires with Mo-Ni content were characterized by a monotonic resistivity increase with the temperature. But the microwires with Cr content had a well-marked resistivity minimum near the temperature Tм ~ 163 °C. This minimum shifted to a temperature value of ~260 °C after annealing. The research shows that the temperature dependence of resistivity in the temperature range below Tм obeys the f(T) = -ln(T) law.

Domain wall mobility engineering by a perpendicular magnetic field in microwires with a gradient of perpendicular anisotropy

Fast domain wall propagation is a typical feature of amorphous glass-coated microwires with positive magnetostriction. The high domain wall velocity can be effectively tailored either by sample postprocessing or temperature. In this work, we show that the domain wall dynamics can be engineered by a perpendicular magnetic field. We perform the domain wall mobility measurements in microwires with a varying gradient of the perpendicular magnetic anisotropy. It is shown that domain wall mobility is mainly determined by counterplay between the amplitude of perpendicular anisotropy and externally applied perpendicular field. The presence of perpendicular magnetic anisotropy is observed by Scanning electron microscopy. The relation between the maximum applied perpendicular magnetic field, and the wire dimensions are provided based on the measured data.

A domain wall creation paradigm: Realization for amorphous Fe-based microwires

The creation of a domain wall pair in the magnetic core of amorphous glass-coated bistable microwires with circular cross-section is studied. Energy balance is formulated in the spirit of particle decay, equalizing magnetic field work and energy of two domain walls, emitted in opposite directions. The critical nucleation field is evaluated and compared with observations.

An Indirect Method of Micromagnetic Structure Estimation in Microwires.

The tunable magnetic properties of amorphous ferromagnetic glass-coated microwires make them suitable for a wide range of applications. Accurate knowledge of the micromagnetic structure is highly desirable since it affects almost all magnetic properties. To select an appropriate wire-sample for a specific application, a deeper understanding of the magnetization reversal process is required, because it determines the measurable response (such as induced voltage waveform and its spectrum). However, the experimental observation of micromagnetic structure of micro-scale amorphous objects has strict size limitations. In this work we proposed a novel experimental technique for evaluating the microstructural characteristics of glass-coated microwires. The cross-sectional permeability distribution in the sample was obtained from impedance measurements at different frequencies. This distribution enables estimation of the prevailing anisotropy in the local region of the wire cross-section. The results obtained were compared with the findings of magnetostatic measurements and remanent state analysis. The advantages and limitations of the methods were discussed.

The Design and Production of a Suitable Carrier for Microwires Used for Non-Contact Detection of Mechanical Strains

During the loading process, strain gauges connected to measuring devices are usually used to detect the strains of structural load-bearing members. Nowadays, newer and more sophisticated measurement methods are being developed. One of these involves the application of amorphous glass-coated microwires for non-contact detection of mechanical strains. This paper presents the results of research work aimed at finding a suitable carrier or transfer medium for such microwires. The identification of a suitable transfer medium was part of extensive theoretical and experimental research focusing on non-contact detection of mechanical strains based on amorphous glass-coated microwires. The results present an innovative and effective approach for sustainable practices in various fields of construction activity.