Magnetic Properties Of Amorphous Microwires Research Articles

Performance of Fluxgate Magnetometer with Cu-Doped CoFeSiB Amorphous Microwire Core.

In this study, we investigated the effects of Cu doping on the performance of CoFeSiB amorphous microwires as the core of a fluxgate magnetometer. The noise performance of fluxgate sensors primarily depends on the crystal structure of constituent materials. CoFeSiB amorphous microwires with varying Cu doping ratios were prepared using melt-extraction technology. The microstructure of microwire configurations was observed using transmission electron microscopy, and the growth of nanocrystalline was examined. Additionally, the magnetic performance of the microwire and the noise of the magnetic fluxgate sensors were tested to establish the relationship between Cu-doped CoFeSiB amorphous wires and sensor noise performance. The results indicated that Cu doping triggers a positive mixing enthalpy and the reduced difference in the atomic radius that enhances the degree of nanocrystalline formation within the system; differential scanning calorimetry analysis indicates that this is due to Cu doping reducing the glass formation capacity of the system. In addition, Cu doping affects the soft magnetic properties of amorphous microwires, with 1% low-doping samples exhibiting better soft magnetic properties. This phenomenon is likely the result of the interaction between nanocrystalline organization and magnetic domains. Furthermore, a Cu doping ratio of 1% yields the best noise performance, aligning with the trend observed in the material's magnetic properties. Therefore, to reduce the noise of the CoFeSiB amorphous wire sensor, the primary goal should be to reduce microscopic defects in amorphous alloys and enhance soft magnetic properties. Cu doping is a superior preparation method which facilitates control over preparation conditions, ensuring the formation of stable amorphous wires with consistent performance.

Cylindrical micro and nanowires: Fabrication, properties and applications

The state of the art in cylindrical nano and micro wires is reviewed with particular emphasis on the latest research trends. We analyze some of the key properties for prospective applications including magnetic anisotropy and micromagnetic structure, spin-caloritronics, domain wall dynamics and its control by transverse magnetic field and induced anisotropy, high frequency impedance and magnetic control of the electric polarizability, shape-memory and magnetocaloric effects in Heusler alloys wires. Cylindrical nanowires present specific magnetic domain configurations as complex vortex and transverse domains while the magnetization reversal typically involves propagation of Bloch-point domain walls. Such magnetic behavior offers new perspectives for applications in advanced technologies including spintronics, logic devices and novel magnetic recording media, functionalization and bioengineering and sensor devises. In particular, rapidly solidified glass-coated amorphous nanowires and submicron wires which constitute a novel class of ultrathin soft magnetic materials are attractive for future micro and nano sensors.Amorphous and nanocrystalline microwires prepared by rapid quenching from the melt can present quite peculiar magnetic properties, like spontaneous magnetic bistability associated with single and large Barkhausen jump and magnetoimpedance effect. Magnetic properties of amorphous microwires are related to the value and sign of the magnetostriction constant since the magnetoelastic anisotropy is one of the main sources of the magnetic anisotropy. As-prepared microwires with positive magnetostriction constant show generally rectangular hysteresis loops and fast domain wall propagation. In the case of low and negative magnetostriction, the wires demonstrate inclined hysteresis loops and large magnetoimpedance. To refine the magnetic structure, the easy anisotropy can be adjusted by annealing in the presence of a magnetic field and/or mechanical stress. Thus, the magnetic bistability in negative magnetostriction wires can be induced by annealing. Minimizing the magnetoelastic anisotropy either by adjusting the chemical composition with a low magnetostriction coefficient or by heat treatment is an appropriate route for enhancing the domain wall velocity. Tailoring the magnetic anisotropy by stress-annealing is also a promising method of the optimization of the domain wall dynamics in magnetic microwires.Soft magnetic properties and tunable magnetic structure of amorphous microwires are responsible for the magnetoimpedance effect, which preserves a high sensitivity up to GHz frequencies. This opens up novel applications based on the electric polarization of a finite-length microwire depending on the wire surface impedance near the antenna resonance, including embedded wireless sensing elements, self-sensing composites and selective microwave materials.Heusler alloys demonstrate the huge variety of physical properties that can be obtained by simple change in composition. Naturally, the efforts have been made to produce Heusler-based nano and micro wires to take advantage of variety of their physical properties in a miniature form. In this review, the emphasis is made on Heusler alloy glass-coated microwires.

The effect of stress distribution in the bulk of a microwire on the magnetization processes

Abstract The effect of tensile stresses on the magnetic properties of amorphous microwires with positive magnetostriction has been studied. It has been determined that the experimental dependence of coercivity on the tensile stresses is reversible and consists of linear and square root parts. The evolution of an average stress level in the “core” and surface domain layer has been theoretically estimated depending on the external tensile stress. The value of internal stress level may vary from 150 to 600 MPa in “core” for microwires with different ratio of amorphous metallic nucleus diameter to thickness of glass shell. Crucial differences of tension of glass-coated and uncoated microwires have been investigated. The analysis of these differences with relation to effect under tension has been performed.

Stress state effect on the magnetic properties of amorphous microwires

The dependence of the magnetic structure and the hysteresis properties of the amorphous microwires on the applied load is investigated by the magnetic-optical method of the indicator films and the inductive pickup coils. We examine the amorphous microwires of Fe73.5Cu1Nb3Si13.5B9 and Fe77.5Si7.5B15, with a positive magnetostriction and different thickness of the glass coating and the diameter of the metal core. An increase in the stress level can be achieved by stretching along a microwire axis. The hysteresis properties and magnetic domain structure are examined during in situ stretching. Coercivity versus tension curves have been plotted for the examined microwires. It is shown that an increase in the stress leads to an increase in the coercivity.

Functional magnetoelectric composites with magnetostrictive microwires

This paper discusses the electric polarization properties of ferromagnetic microwires at microwave frequencies. At the vicinity of the antenna resonance, a strong magnetic control of the wire polarization is possible owing to the magnetoimpedance (MI) effect. In order to realize efficient tunable properties, magnetic microwires of Co-rich compositions in amorphous state are considered. The absence of the crystalline structure is an important condition to establish well-defined magnetic anisotropies of small magnitudes, which results in the magnetization processes sensitive to the external parameters such as a magnetic field and a mechanical stress. Tunable soft magnetic properties of amorphous microwires are responsible for the MI effect, which can be observed at high frequencies (1–10 GHz). Here we demonstrate that the electric polarization of a microwire depends on its impedance and, hence, can be modulated changing the wire magnetization state in response to the application of a magnetic field and a mechanical stress. The polarization problem is treated theoretically by solving the scattering problem from a cylindrical ferromagnetic wire with the impedance boundary conditions. The modelling results agree well with the available experimental data.

Stress Effects on Magnetic Properties of Amorphous Microwires Subjected to Current Annealing

Effects of current annealing on magnetic hysteresis properties and magnetoimpedance (MI) of glass-coated amorphous microwires with nominal composition of Co71Fe5B11Si10Cr3 and small positive magnetostriction were investigated with the purpose to control the magnetic anisotropy. We have demonstrated that current annealing can produce a controllable change in the easy anisotropy direction from almost axial to circular, depending on the annealing time. The induced magnetization configuration is very sensitive to the applied tensile stress. The combination of positive magnetostriction and helical anisotropy makes it possible to realise large stress-magnetoimpedance (S-MI) effect without use of any dc bias fields owing to the directional change in magnetization. This is especially important for microwave frequency S-MI effect and can be very interesting for developing stress-sensors operating at the high frequency region.

Effect of Temperature and Time of Stress Annealing on Magnetic Properties of Amorphous Microwires

E ect of Temperature and Time of Stress Annealing on Magnetic Properties of Amorphous Microwires K. Chichay, V. Rodionova, M. Ipatov, V. Zhukova and A. Zhukov Innovation Park and Institute of Physics and Technology, Immanuel Kant Baltic Federal University, Kaliningrad, 236041, Russia National University of Science and Technology MISIS , Moscow, 119049, Russia Dpto. Fisica de Materiales, Fac. Quimicas, UPV/EHU, San Sebastian, 20009, Spain IKERBASQUE, Basque Foundation for Science, Bilbao, 48011, Spain

Studies of Magnetic Properties of Amorphous Microwires Produced by Combination of by Quenching, Glass Removal and Drawing Techniques

In this paper we report on fabrication and characterization of nearly-zero magnetostriction Co69Fe4Cr4Si12B11amorphous microwires produced by two different methods: i-fabricated by combination of usual Tailor-Ulitovski method allowing rapid quenching of composite glass coated microwires following by glass removal techniques (with diameter about 90 μm); ii-produced by Tailor-Ulitovski method with consequent glass removal and warm drawing (at 300 °C). In first case the metallic nucleus diameter has been about 90 μm and after drawing we obtained microwires with diameter about 55 μm. Drawn samples have been annealed at temperatures between 250 and 450 °C. We studied GMI effect (dependence of impedance, Z, on applied magnetic field H) and hysteretic magnetic properties in produced microwires. Ferromagnetic magnetic without glass coating with good magnetic and mechanical properties and GMI effect have been obtained. We can tailor the microwires magnetic properties for its application in magnetic sensors through the selection of adequate thermal treatment conditions.

Susceptibility Spectroscopy in FeNiSiB Microwires

Amorphous magnetic microwires are novel materials, which are characterized by unusual soft magnetic properties, such as magnetic bistability and Giant MagnetoImpedance (GMI) effect [1]. The magnetic behavior of this microwire strongly depends on their composition, which is directly responsible of the sign and magnitude of magnetostriction constant, and also on the values and distribution of internal stresses induced during preparation [2]. The magnetic properties of amorphous microwires are usually described in terms of the core-shell model [3]. In accordance with the model, a microwire with positive magnetostriction consists of one large axial domain surrounded by the outer domains with radially oriented magnetization. Measurement of the amplitude dependence of the complex susceptibility is a useful method for studying dynamic magnetization processes in ferromagnetic materials because the magnetization processes can be resolved [4, 5]. We apply this method here to study the magnetization process in amorphous glass-coated FeNiSiB microwires with different Fe/Ni ratios.