Glass-coated Magnetic Microwires Research Articles

Non-Destructive Testing of Pipe Conveyor Belts Using Glass-Coated Magnetic Microwires

Belt conveyors have been used in a wide range of applications because in comparison to the alternative solutions represented by the rail or road transportation, their operation is typically more cost effective, with lower energy demands and the possibility of utilizing renewable energy sources, and during their operation, less noise and air pollution is produced. The presented article is focused on pipe belt conveyors that are even more sustainable and in harmony with the environment, especially considering transportation of fine and dusty materials. More specifically, pipe belt conveyors have the possibility of utilizing microwires as a sensing element for microwire-based sensors for the pipe belt conveyor diagnostics from a mechanical loading point of view. This is because during the enclosing of the pipe conveyor belt, periodical cyclical mechanical loading is applied due to the bending. From the results of the performed set of FEM (Finite Element Method) analyses of the glass-coated magnetic microwires, it can be concluded that during the selection process of the microwires, emphasis should be directed the thickness of the glass coating, which can affect the lifetime of the microwire significantly. The microwire length has negligible influence on the estimated number of bending cycles until the damage or crack occurs.

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

Ferromagnetic glass-coated microwires for cell manipulation

The application of magnetic nanoparticles allows labeling the cell for its manipulation via the external magnetic field. In this work, it is proposed to use glass-coated magnetic microwires as a magnetic pin system to create a strong and well-localized magnetic field at the end of such microwires. Magnetic microwires manufactured by the Taylor − Ulitovsky method exhibit tunable magnetic properties correlated with their unique micromagnetic structure. The control of magnetic properties can be achieved by, for example, the chemical composition of the wire: Fe-based microwire shows bistable hysteresis and thus strong stray fields at the ends, while Co-based one demonstrates S-shaped hysteresis with almost zero remanent magnetization because of a closed domain structure. In this research, we discovered by theoretical calculation and experiments the usability of both kinds of microwires for different approaches of cell manipulations.

Field and Current Controlled Domain Wall Propagation in Twisted Glass-Coated Magnetic Microwires

The torsion effect on the field and current driven magnetization reversal and the associated domain wall velocity in cylindrical amorphous and nanocrystalline glass-coated microwires is reported. Samples from three representative compositions have been investigated: (1) amorphous Fe77.5Si7.5B15 with positive magnetostriction, λ ≅ 25 × 10−6, (2) amorphous Co68.18Fe4.32Si12.5B15 with nearly zero negative magnetostriction, λ ≅ −1 × 10−7, and (3) nanocrystalline Fe73.5Si13.5B9Cu1Nb3 (FINEMET) with small positive magnetostriction, λ ≅ 2.1 × 10−6, all having the diameter of the metallic nucleus, d, of 20 µm and the glass coating thickness, tg, of 11 µm. The results are explained through a phenomenological interpretation of the effects of applied torque on the anisotropy axes within the microwires with different characteristics. Among all the complex mechanical deformations caused by the application of torque on magnetic microwire samples, the most important are the axial compression – for axial field-driven domain wall motion, and the circumferential tension – for electrical current/circumferential field-driven domain wall motion. The Co68.18Fe4.32Si12.5B15 microwire, annealed at 300 °C for 1 hour and twisted at 168 Rad/m exhibits the optimum characteristics, e.g. the lowest switching current (down to 9 mA~2.9 × 10−3 A/cm2) and the largest domain wall velocity (up to 2300 m/s).

Glass-coated Ni2MnGa microwires with narrow structural transition range and enhanced magnetocaloric effect at low fields

The structural, magnetic and magnetocaloric properties of glass-coated magnetic microwires, composed of Ni2MnGa and produced with the Taylor-Ulitovski technique, have been investigated with XRD, EBSD, SEM and magnetization measurements. At room temperature, the microwires exhibit a monocrystalline phase with a Cu2MnAl-type crystal structure (space group Fm-3m; cell parameter a = 5.832 Å). The microwires in this study show a magnetocaloric effect with a sharp martensitic transformation in the range of 185–195 K, as well as a magnetocaloric effect owing to the magnetic phase transition at the Curie temperature. Due to the different strength of anisotropy and easy magnetization axis, the magnetocaloric effect during the martensitic transformation exhibit a maximum at low fields (0.5 T), and high efficiency (defined as a ratio between refrigerant capacity and applied magnetic field) at 0.2 T.

Technology, Preparation and Properties of the Cast Glass-Coated Magnetic Microwires

Magnetic properties of cast amorphous and nanocrystalline microwires have been reviewed considering their potential application. Microwires were produced from Co Fe Mn Cr Cu B and Si using the Taylor–Ulitovsky method. Technological aspects of the Taylor–Ulitovsky method for fabrication of glass-coated microwire with different structure are analyzed. Magnetic microwires demonstrate a large variety of magnetic behaviors, which is important for sensing applications. Depending on the chemical composition of the metallic core, for Co-, Fe- and Ni-based composition, the microwires’ properties are very different. The geometrical characteristics (diameter of metallic core and thickness of the glass) of the microwire depend on the physical properties of a metallic composition and of glass and the parameters of the heating inductor and the speed of obtaining a microwire. The diameter of metallic core in these microwires can range from 0.5 to 70 μm, and their thickness of the glass can vary from 1 to 50 μm.

Mechanical Stress Dependence of the Switching Field in Amorphous Microwires

Glass-coated magnetic microwires belong to a unique rank among materials that have high potential to be used in new technologies. We have studied the possibility to employ amorphous bistable microwires as a sensor for bending of carbon fiber composite. The measurement of switching time instead of switching field drastically increases the sensitivity of such sensors up to 380% for positive bending and 125% for negative bending. The results show that microwires applied on the surface structures of the materials can be used as sensors of mechanical stresses or bending.

Influence of Fixation on Magnetic Properties of Glass-Coated Magnetic Microwires for Biomedical Applications

The control of biomechanical processes in the tissue-implant interface and thermal changes created by friction or inflammatory processes in the implant and its environment represent the key validating processes of the postimplanting process. It is crucial for a patient and their health to minimize the invasiveness of the temperature measuring processes and the inner mechanical stress in the implant-tissue interface. For the purpose of these measurements, amorphous magnetic glass-coated microwires are the most suitable. Compared with other sensors, such as radio frequency identification sensors, the microwires have a significant advantage due to their dimensions (~2 cm × 50 μm) (because of which the sensor almost does not interfere with the inner implant structures), their production is relatively cheap, and only ~ 20 mm microwire is needed for the functional sensor. This paper is concerned with the testing of more types of microwire fixation in an implant and the impact of the fixation; it deals with necessary magnetic properties of a microwire and their dependence on the temperature. Microwire made of master alloy Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">78</sub> W <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sub> B <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">17</sub> was created and fixed in four ways: 1) on one end; 2) on two ends; 3) in the middle; and 4) along its full length. The results show that the optimal way of fixation is the one along the full length of a microwire; however, the final signal is influenced by both, the type and volume of the applied fixation material. The highest sensitivity of the designed microwire was in the range of 120-140 °C with no fixation and only with the full length fixation, this sensitivity decreased to 40-50 °C, which is a level close to the level required for biomedical applications (35-42 °C).

Possibile Applications of Magnetic Microwires in Aviation

Abstract Magnetic microwires have been rediscovered due to a number of the unusual magnetic properties and their potential applications. The paper concerns glass-coated magnetic microwires composed of a ferromagnetic metallic core with a diameter of 0.6 - 30 jj.m and of a glass coat with a thickness of 2 - 20 jj.m. The fabrication process and magnetic properties of these microwires are described. Due to their unique properties microwires can be used as a sensing element of sensors. Microwire-based sensors can be used in a wide range of aviation applications as magnetic field sensors, tensile stress sensors or temperature sensors. The main advantages of microwire-based sensors are associated with their small dimensions and weight, which play a very important role in aviation.

Thermal Conductivity and Diffusivity Measurements of Glass-Coated Magnetic Microwires Using Lock-in Thermography

Magnetic microwires (with a diameter of a few tens of micrometers) have been introduced in the last years following the tendency in miniaturization of magnetic sensor devices. The aim of this work is to measure the thermal diffusivity \((D)\) and thermal conductivity \((K)\) of coated magnetic microwires made of a metallic core with glass coating. Both thermal properties are measured in amorphous and crystalline states. Lock-in infrared thermography, using a modulated and focused laser beam to heat the sample, is specially suited to study heat propagation along the wire.

Micromagnetic Simulation on the Microwave Magnetic Properties of Glass-Coated Amorphous Alloy Microwires

The magnetic structure of the glass-coated magnetic alloy microwires were modeled based on the main magnetic domain structure and meshed by finite element method. The magnetic spectrum of the magnetic alloy microwires was calculated based on the micromagnetic theory. The simulation results of the magnetic spectrum of glass-coated magnetic alloy microwires showed that the magnetic anisotropy field increase as the magneto-crystalline anisotropy constants increase. The microwave resonance frequency increased accompanied by the reduction of the permeability and the increase of the magnetic anisotropy field of the glass-coated magnetic alloy microwires.

Simulation of the Diameters, Length and Content Effect on the Magnetic Properties of Glass-Coated Magnetic Alloy Microwires

The microwave permeability of glass-coated magnetic alloy microwires / dielectric composite was investigated by apparent permeability linked with intrinsic permeability calculated based on Landau-Lifshitz function. The effect of diameter, length and microwires content on the composite effective permeability was simulated. The simulated results show that the complex permeability decreases with the increase of the microwires diameter and the wire content in the composite. The microwave magnetic resonance frequency increase distinctly with the lengthening of the glass-coated microwires. The full width at half maximum of the ferromagnetic resonance peak increases with the lengthening of the microwires and the decrease of the wire content.

Influence of the magnetoelastic anisotropy on the domain wall dynamics in bistable amorphous wires

We deal with the influence of the applied stress on the domain wall velocity in glass-coated magnetic microwires. In general, the domain wall velocity decreases with the applied tensile stress. Four regimes of the domain wall dynamics appear: (1) diffusion-damped, (2) a regime with variable domain wall width, (3) a viscous and (4) a vortex regime. Detailed analysis of domain wall parameters shows that the structural relaxation plays an important role even at ambient temperatures if high tensile stress is present. At higher fields (viscous regime), the most important damping arises from magnetic relaxation of magnetic moments. Finally, the domain wall velocity steeply increases (reaching a maximum at 7000 m s−1) in the vortex regime and so does the domain wall mobility.

Magnetostatic interaction of glass-coated magnetic microwires

We report on tailoring the hysteresis loops of arrays containing Fe- and Co-rich microwires utilizing effects of magnetostatic coupling. The interacting wires of both types may produce a complex magnetic response and highly specific spectral characteristics. For Fe-rich microwires we observed step-wise hysteresis loops with a number of Barkhausen jumps equal to a number of Fe-rich microwires. For arrays of Co-based microwires the change in the hysteresis loop shape is less pronounced and is characterized by an increase in the magnetic anisotropy due to interwire interactions. The most interesting multistage magnetization behavior is obtained for arrays containing both types of wires and is characterized by field intervals with both gradual and abrupt magnetization changes. We also investigated the spectral properties associated with each type of magnetization process. The field plots for higher harmonics are highly specific and can be used to discriminate the types of wires in the array.

Influence of varying metal-to-glass ratio on GMI effect in [formula omitted] amorphous glass-coated microwires

The influence of a varying metal-to-glass ratio on the GMI effect in amorphous glass-coated Co 70.3Fe 3.7B 10Si 13Cr 3 microwires has been investigated. In the range of frequencies investigated (1–10 MHz), the magnitude of the GMI effect increases as the metal-to-glass ratio ( h ) increases from 4.11 to 9.29. The GMI curves for the h = 4.11 microwire exhibit a single-peak feature for f ≤ 1 MHz and a double-peak feature for f > 1 MHz, whereas a consistent double-peak feature is observed for microwires with h = 8.07 , 8.72 , and 9.29. The largest GMI effect is achieved for microwires with h = 9.29 . The anisotropy field ( H k ) , determined from GMI curves, increases with h = 4.11 to h = 8.07 and decreases when h > 8.07 . The calculated radial stress decreases as h increases from 4.11 to 9.29. These results provide further insights into the correlation between the GMI effect and microwire dimensions towards the GMI optimization of amorphous glass-coated magnetic microwires for sensor applications.

Thermal Annealing Influence on Magnetic and Structural Properties of Cu56Ga28Mn16 Microwires

AbstractWe report on the crystalline structure, morphology and thermomagnetic properties of glass-coated magnetic microwires with Cu56Ga28Mn16 composition, as well as the thermal annealing influence on its magneto-structural properties. As-cast CuMnGa microwires exhibit a majority cubic B2 phase, and upon annealing at temperatures up to 573 K a new hexagonal phase appears coexisting with the cubic B2 major phase. Thermal annealing treatments also shift the Curie temperature about 150 K with respect to the one for the as-cast microwire. Furthermore, the signature of a structural phase transition is observed for the microwire annealed at 523 K

Fe–(Au,Cu)–B two-phase magnetic microwires with exchange coupled nanosized grains

Results on the magnetic behavior of glass-coated magnetic microwires prepared from the Fe87Au2−xCuxB11 alloy system are reported for the first time. The changes induced in their axial magnetization process by the substitution of Au with Cu have been studied. Hysteresis loops with typical shapes for soft magnetic materials have been observed in all cases except for x=1.5at.% of Cu. Fe87Au0.5Cu1.5B11 microwires display a two-step hysteresis loop with a plateau at zero magnetization. The observed change in the axial magnetization process of Fe–(Au,Cu)–B microwires with Cu content has been explained considering the average distance among adjacent α‐(Fe,Cu) nanosized grains to be smaller than the exchange length. In this way, the ensemble of grains is collectively magnetized and it behaves as a single material from the magnetic point of view. The remainder amorphous matrix is also collectively magnetized, and the resulting stepped loop is the result of the magnetostatic coupling between these two systems: the grain ensemble and the amorphous matrix. The results demonstrate the effectiveness of composition control on the magnetic properties of Fe–(Au,Cu)–B microwires and open up new application opportunities for glass-coated microwires.

Domain-wall dynamics in glass-coated magnetic microwires

Glass-coated magnetic microwires with positive magnetostriction show peculiar domain structure that consists mostly of one large domain with magnetization-oriented axially. It was shown that small closure domains appear at the end of the microwire in order to decrease the stray fields. As a result of such domain structure, the magnetization reversal in axial direction runs through the depinning of one of such closure domains and subsequent propagation of the corresponding domain wall. Quite unusual domain-wall (DW) dynamics of the DW propagation predicted previously from the theory has been found in such amorphous microwires. In this paper, we are dealing with the DW dynamics of glass-coated microwires with small positive magnetostriction. The DW damping coming from the structural relaxation dominates at low temperatures as a result of the decrease of the mobility of the structural atomic-level defects. Negative critical propagation field points to the possible DW propagation without applied magnetic field. Probable explanation could be in terms of the effective mass of the DW.

Tailoring of magnetic anisotropy in Fe-rich glass-coated magnetic microwires by thermo-mechanical annealing

The effect of thermal treatments such as conventional furnace annealing (CA) and annealing under tensile stress (SA) on the hysteretic magnetic properties of Fe74B13Si11C2 glass-coated microwires has been studied. CA treatment does not change the character of the hysteresis loop but coercivity, Hc, slightly decreases due to the internal stress relaxation. Under certain SA conditions (annealing temperature, Tann > 300 ◦ C, applied stress, σ> 700 MPa) the hysteresis loop becomes inclined with transverse anisotropy field about 1500 A/m. This modification of the hysteresis loop has been interpreted in terms of the change of the easy magnetization direction from axial to a transverse direction. On the other hand, samples subjected to stress annealing show noticeable (12%) magneto-impedance effect in spite of their large magnetostriction. Finally, application of tensile stresses to the stress-annealed sample results in the recovering of the rectangular hysteresis loop typical for the as-prepared state. This processing allows the tailoring of magnetic anisotropy in these microwires which is of interest for technological purposes. © 2003 Elsevier B.V. All rights reserved.

Stress induced magnetic anisotropy and giant magnetoimpedance in Fe-rich glass-coated magnetic microwires

The effect of conventional (CA) and stress annealing (SA) on magnetic properties of Fe74B13Si11C2 glass-coated microwires has been studied. CA treatment does not significantly change the character of the hysteresis loop. Under certain annealing conditions (annealing temperature, Tann&amp;gt;300 °C, applied stress, σ&amp;gt;700 MPa) rectangular hysteresis loop transforms into the inclined with magnetic anisotropy field above 1000 A/m. Such phenomenology has been related to the induction of transverse magnetic anisotropy by SA treatment. Under tensile stress the SA annealed microwire recovers rectangular hysteresis loop. Samples subjected to stress annealing show noticeable magnetoimpedance and stress impedance effects in spite of their large magnetostriction.