Search Results (6)

Glass-coated microwires exhibiting magnetic bistability have garnered significant attention as promising wireless sensing elements, primarily due to their rapid magnetization switching capabilities. These microwires consist of a metallic core with diameter d, encased in a glass coating, with a total diameter D. In this study, we investigated how the dimensions of both components and their ratio (d/D) influence the magnetization reversal behavior of Fe-based microwires. While previous studies have focused on either d or d/D individually, our research uniquely considered the combined effect of both parameters to provide a comprehensive understanding of their impact on magnetic properties. The metallic core diameter d varied from 10 to 19 µm and the d/D ratio was in the range of 0.48–0.68. To assess the magnetic properties of these microwires, including the shape of the hysteresis loop, coercivity, remanent magnetization, and the critical length of bistability, we employed vibrating sample magnetometry in conjunction with FORC-analysis. Additionally, to determine the critical length of bistability, magnetic measurements were conducted on microwires with various lengths, ranging from 1.5 cm down to 0.05 cm. Our findings reveal that coercivity is primarily dependent on the d/D parameter. These observations are effectively explained through an analysis that considers the competition between magnetostatic and magnetoelastic anisotropy energies. This comprehensive study paves the way for the tailored design of glass-coated microwires for diverse wireless sensing applications. Full article

In the current study we have obtained Co₂FeSi glass-coated microwires with different geometrical aspect ratios, ρ = d/D_tot (diameter of metallic nucleus, d and total diameter, D_tot). The structure and magnetic properties are investigated at a wide range of temperatures. XRD analysis illustrates a notable change in the microstructure by increasing the aspect ratio of Co₂FeSi-glass-coated microwires. The amorphous structure is detected for the sample with the lowest aspect ratio (ρ = 0.23), whereas a growth of crystalline structure is observed in the other samples (aspect ratio ρ = 0.30 and 0.43). This change in the microstructure properties correlates with dramatic changing in magnetic properties. For the sample with the lowest ρ-ratio, non-perfect square loops are obtained with low normalized remanent magnetization. A notable enhancement in the squareness and coercivity are obtained by increasing ρ-ratio. Changing the internal stresses strongly affects the microstructure, resulting in a complex magnetic reversal process. The thermomagnetic curves show large irreversibility for the Co₂FeSi with low ρ-ratio. Meanwhile, if we increase the ρ-ratio, the sample shows perfect ferromagnetic behavior without irreversibility. The current result illustrates the ability to control the microstructure and magnetic properties of Co₂FeSi glass-coated microwires by changing only their geometric properties without performing any additional heat treatment. The modification of geometric parameters of Co₂FeSi glass-coated microwires allows to obtain microwires that exhibit an unusual magnetization behavior that offers opportunities to understand the phenomena of various types of magnetic domain structures, which is essentially helpful for designing sensing devices based on thermal magnetization switching. Full article

Fe–based metallic microwires possess unique microstructure and size effects, exhibiting favorable mechanical, electrical, and magnetic properties, thus distinguishing them as a possible agents for use as microwave absorbing materials. In this paper, the absorbing properties of Ni–doped Fe–based metallic microwires optimized by orthogonal experiments were investigated, and based on the optimal parameters, the influencing mechanism of the Ni doping amount on the absorbing properties was further analyzed. It was noted that at the frequency f = 8.36 GHz, the maximum reflection loss R_L and electromagnetic wave absorption efficiency A_eff can reach −54.89 dB and 99.999%, respectively. Moreover, the Ni doping amount could result in the improved wave-absorbing properties of composites, obtain the corresponding optimal parameters, and even change the position of the maximum absorption peak, which are all of great significance for practical engineering applications. Full article

Herein, the effect of Ni-doping amount on microstructure, magnetic and mechanical properties of Fe-based metallic microwires was systematically investigated further to reveal the influence mechanism of Ni-doping on the microstructure and properties of metallic microwires. Experimental results indicate that the rotated-dipping Fe-based microwires structure is an amorphous and nanocrystalline biphasic structure; the wire surface is smooth, uniform and continuous, without obvious macro- and micro-defects that have favorable thermal stability; and moreover, the degree of wire structure order increases with an increase in Ni-doping amount. Meanwhile, FeSiBNi2 microwires possess the better softly magnetic properties than the other wires with different Ni-doping, and their main magnetic performance indexes of M_s, M_r, H_c and μ_m are 174.06 emu/g, 10.82 emu/g, 33.08 Oe and 0.43, respectively. Appropriate Ni-doping amount can effectively improve the tensile strength of Fe-based microwires, and the tensile strength of FeSiBNi3 microwires is the largest of all, reaching 2518 MPa. Weibull statistical analysis also indicates that the fracture reliability of FeSiBNi2 microwires is much better and its fracture threshold value σ_u is 1488 MPa. However, Fe-based microwires on macroscopic exhibit the brittle fracture feature, and the angle of sideview fracture θ decreases as Ni-doping amount increases, which also reveals the certain plasticity due to a certain amount of nanocrystalline in the microwires structure, also including a huge amount of shear bands in the sideview fracture and a few molten drops in the cross-section fracture. Therefore, Ni-doped Fe-based metallic microwires can be used as the functional integrated materials in practical engineering application as for their unique magnetic and mechanical performances. Full article

Co-based amorphous microwires presenting the giant magnetoimpedance effect are proposed as sensing elements for high sensitivity biosensors. In this work we report an experimental method for contactless detection of stress, temperature, and liquid concentration with application in medical sensors using the giant magnetoimpedance effect on microwires in the GHz range. The method is based on the scattering of electromagnetic microwaves by FeCoSiB amorphous metallic microwires. A modulation of the scattering parameter is achieved by applying a magnetic bias field that tunes the magnetic permeability of the ferromagnetic microwires. We demonstrate that the OFF/ON switching of the bias activates or cancels the amorphous ferromagnetic microwires (AFMW) antenna behavior. We show the advantages of measuring the performing time dependent frequency sweeps. In this case, the AC-bias modulation of the scattering coefficient versus frequency may be clearly appreciated. Furthermore, this modulation is enhanced by using arrays of microwires with an increasing number of individual microwires according to the antenna radiation theory. Transmission spectra show significant changes in the range of 3 dB for a relatively weak magnetic field of 15 Oe. A demonstration of the possibilities of the method for biomedical applications is shown by means of wireless temperature detector from 0 to 100 °C. Full article

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. Full article