Length Of Microwires Research Articles

Development of amorphous microwires with graded magnetic anisotropy

We observed that the annealing at variable temperature allows to develop amorphous magnetic microwires with graded magnetic anisotropy. In such microwires, annealed with a temperature gradient, gradual variation of the hysteresis loops along the microwire length is observed. The peculiarity of such microwires with graded magnetic anisotropy and rectangular hysteresis loops is that in such microwires the energy landscape and hence the domain wall features, such as the domain wall velocity can be effectively controlled. Obtained spatial distribution of magnetic anisotropy must be attributed to a gradual modification of the domain structure along the length of the microwires annealed in a temperature gradient.Accordingly, we propose a rather simple route involving -annealing in a temperature gradient to design graded magnetic anisotropy in magnetic microwires.

Determination of Magnetic Structures in Magnetic Microwires with Longitudinally Distributed Magnetic Anisotropy.

We studied the magnetic properties of a glass-covered amorphous microwire that was stress-annealed at temperatures distributed along the microwire length. The Sixtus-Tonks, Kerr effect microscopy and magnetic impedance techniques have been applied. There was a transformation of the magnetic structure across the zones subjected to annealing at different temperatures. The annealing temperature distribution induces the graded magnetic anisotropy in the studied sample. The variety of the surface domain structures depending on the longitudinal location has been discovered. Spiral, circular, curved, elliptic and longitudinal domain structures coexist and replace each other in the process of magnetization reversal. The analysis of the obtained results was carried out based on the calculations of the magnetic structure, assuming the distribution of internal stresses.

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.

Graded magnetic anisotropy in Co-rich microwires

A gradual change in the hysteresis loop of Co-rich glass-coated microwire sample stress-annealed at variable temperature is observed. Such microwire annealed with a temperature gradient presents also variable squareness ratio along the microwire length, L. Obtained graded anisotropy has been attributed to a gradual modification of the domain structure along the microwire. Accordingly, we propose a rather simple route to design graded magnetic anisotropy in a magnetic microwire.

Thermoelectric microgenerators using a single large-scale Sb doped ZnO microwires

The large-scale ZnO microwires (MWs) arrays with different Sb doping concentrations were grown by chemical vapor deposition method without using metal catalyst or seed layer. The diameter and length of MWs were about 20–50 μm and 1–2.5 cm, respectively. The experimental results indicated that the length and orientation of ZnO MWs were improved gradually with increasing Sb concentration. The surfactant effect of Sb should be the major improvement reason. Furthermore, thermoelectric microgenerators based on single Sb doped ZnO MW have been fabricated on a glass substrate, which can generated maximum output voltage of 68 mV and maximum output current of 782 nA under a temperature difference of 20 K between the two electrodes. The single Sb doped ZnO MW showed a Seebeck coefficient of about 3.4 mV/K. In addition, the output current of the device was increased dramatically in ultraviolet (UV) illumination compared to dark conditions. The detail of the UV irradiation enhanced output properties of microgenerator was also discussed.

Influence of current annealing and length of microwires on GMI effect

Influence of current annealing and length of microwires on GMI effect

Structural and magnetic properties of “thick” microwires produced by the modernized Ulitovsky–Tailor method

In this article the results on the detailed investigation of the structural, elastic and magnetic properties of the “thick” Fe73,5Si13,5B9Nb3Cu1 and Fe31Co34Ni10(SiB)25 amorphous microwires with the glass shell, produced by the modernized Ulitovsky–Tailor method, are presented. The diameter of the metallic core of microwires was varied from 50 to 200µm. It was found that the core has the stable geometric parameters along the microwire length and the smooth (almost without defects) surface. The studied samples are characterized by the weak dispersion of magnetic anisotropy of the near-surface layers and the high homogeneity of the near-surface local magnetic properties. Furthermore, the microwires exhibit the high plasticity and strength. They are not destroyed even after their full tightening into a knot. The strong influence of tensile stress and torsion on the magnetic properties of the microwires was discovered. The comparison of magneto-field behavior of the studied samples was performed.

Broadband supercontinuum generation in all-normal dispersion chalcogenide microwires.

We report the first chalcogenide microwire designed with all-normal dispersion to generate supercontinuum by optical wave breaking, a low-noise nonlinear process. The chalcogenide (As2S3) microwire is coated with PMMA and tapered to a diameter of 0.58 μm to achieve the all-normal dispersion regime. The generated supercontinuum spectrum spans over an octave from 960 to >2500 nm using a microwire length of only 3 mm and a low pulse energy of 150 pJ.

Fast Magnetization Switching in Amorphous Microwires

We studied the magnetization switching in magnetically bistable amorphous ferromagnetic microwires. We observed quite fast domain wall propagation along the microwires and a correlation between the magnetoelastic anisotropy, distribution of the local nucleation eld along the length of microwire and the domain wall dynamics. We observed that both DW velocity and the range of elds, limiting single DW dynamics, can be manipulated by internal or applied stresses and by annealing. We also observed that under certain conditions a controllable domain wall (DW) collision can be realized in di erent parts of the wire, and that it is possible to manipulate the DW dynamics in a eld-driven regime.

Magnetic Properties of Glass-Coated FeWB Microwires

We have studied magnetization process in amorphous bistable Fe80W3B17 microwires with reduced Curie temperature. High mechanical stresses from glass-coating, induced during production process, result in high switching eld. Reducing the length of microwire, the switching eld decreases as a result of reduction of magnetoelastic anisotropy. Moreover, the decrease of magnetoelastic anisotropy results in a complex temperature dependence of the switching eld. On the other hand, strong variations of the switching eld with temperature can be employed in miniaturised temperature sensor.

Omni-Directional Selective Shielding Multilayered Material for High Frequency Radiation

The selective microwave absorption properties of individual and multiple CoFe-glass coated amorphous microwires (GCAW) with small negative value of magnetostriction <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$(\lambda\sim-1\times 10^{-7})$</tex></formula> , positioned in various configurations are investigated. The deep minimum in the transmission spectra correspond to the first antenna resonance for each length of the individual microwire indicating a selective stop filter behavior. A new type of shielding material in the shape of a multilayered material based on CoFe-GCAW with desired shielding effectiveness and selective absorption of the microwave frequency range by controlling the number of the layers and the length of microwires is proposed and the omni-directional selective shielding properties in the microwave frequency range are determinated. The shielding effectiveness measurements results were <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">${\rm SE}=4\ {\rm dB}$</tex></formula> to 9.5 dB for the samples with two layers, <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">${\rm SE}=18\ {\rm dB}$</tex></formula> to 33 dB for sample with 14 layers, and <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">${\rm SE}=36\ {\rm dB}$</tex></formula> to 48 dB for sample with 28 layers, respectively.

Mid-infrared sources based on the soliton self-frequency shift

We present a method to maximize the soliton self-frequency shift (SSFS) in microwires with diameter profiles varying nonuniformly along the soliton propagation path. The method is divided into two steps. The first step consists in selecting the input microwire diameter that leads to the highest rate of frequency shift per unit of propagation length. The second step consists in increasing gradually the microwire diameter along the soliton path to suppress dispersive wave emission and maintain a large rate of frequency shift per unit of propagation length. We first propose and apply a rule to select the initial diameter using the adiabatic theory. The optimal diameter profile is then achieved by maintaining the redshifting soliton at a fixed spectral separation from the zero-dispersion wavelengths. The optimized profile supports solitons with different input energies that allow a wavelength shift up to 650&#xA0;nm from the 2100&#xA0;nm pump wavelength in a 20&#xA0;cm microwire length. We compare our results with the SSFS generated in microwires with uniform diameter profile to illustrate the enhancement of wavelength shift in the designed nonuniform microwire.

Omni-directional selective shielding material based on amorphous glass coated microwires

The shielding effectiveness of the omni-directional selective shielding material based on CoFe-glass coated amorphous wires in 0.8 GHz-3 GHz microwave frequency range is investigated. The measurements were done in a controlled medium using a TEM cell and in the free space using horn antennas, respectively. Experimental results indicate that the composite shielding material can be developed with desired shielding effectiveness and selective absorption of the microwave frequency range by controlling the number of the layers and the length of microwires.

Wire-length effect on GMI in Co 70.3Fe 3.7B 10Si 13Cr 3 amorphous glass-coated microwires

The sample length dependence of giant magnetoimpedance (GMI) in Co 70.3Fe 3.7B 10Si 13Cr 3 amorphous glass-coated microwires has been studied experimentally and theoretically in the frequency range of 1–10 MHz. It has been shown that there exists a critical microwire length, below which the GMI effect is favored in shorter microwires and above which longer microwires possess a more sensitive dependence of the real component of the impedance to the frequency variation. It is demonstrated that once the resistance of the microwires of varied length is determined, it is possible to evaluate the change in GMI profiles with respect to the change of wire length. The simplified skin-effect model has been found to well explain the observed behaviors.

Magnetorheology of submicron diameter iron microwires dispersed in siliconeoil

We investigate the magnetorheological (MR) properties of suspensions containingiron microwires with 260 nm diameter and two distinct length distributions of5.4 ± 5.2 µm and 7.6 ± 5.1 µm suspended in silicone oil (0.45 Pa s). The rheological properties of these fluids were determinedusing a parallel plate rheometer equipped with a variable strength electromagnet. Theshear stress was measured as a function of shear rate for increasing applied magnetic fields.These results were modeled using the Bingham-plastic constitutive model to determine theapparent yield stress and viscosity as a function of increasing volume fraction and lengthof microwires. At a saturated magnetic flux density, the yield stress using the5.4 µm microwires was found to be 0.65, 2.23, and 4.76 kPa for the 2, 4, and 6 vol% suspensions, respectively. Forthe 7.6 µm wires, the yield stress increases to 8.2 kPa for the 6 vol% suspension. Compared withconventional MR fluids employing spherical particles, the degree of settling is markedlydecreased in the microwire-based fluids. At 6 vol%, conventional fluids display appreciablesettling whereas the microwire-based fluids display no discernable settling. Moreover, therod-shaped microwires are shown to increase the yield stress of the fluids and enhance theMR performance.

Large enhancement of GMI effect in polymer composites containing Co-based ferromagnetic microwires

A new kind of composite material consisting of parallel Co-based ferromagnetic microwires embedded in a polymer matrix was designed and produced for high-performance sensor applications. A great enhancement of the giant magnetoimpedance (GMI) effect and its field sensitivity was achieved in these composite materials. It was found that the GMI effect strongly increased with increasing number of ferromagnetic microwires. At a given frequency of 10 MHz, the GMI ratio and its field sensitivity reached the highest values of 450% and 45%/Oe for the composite containing four microwires when compared with those of 14% and 1%/Oe for that containing one microwire. This indicates that the newly developed composite material is very promising for high-performance GMI sensor applications. It was revealed that the increase of the GMI effect in the composite sample was attributed to the decrease of electrical resistance and the increase of effective permeability. An increase of GMI effect with reducing microwire length was also observed and attributed to decrease of the electrical resistance.