Magnetostrictive Amorphous Wires Research Articles

Direct observation of magnetic domain walls in glass-coated submicronic amorphous wires

Results on the magnetic domain walls in rapidly solidified magnetostrictive and non-magnetostrictive amorphous submicronic wires are reported. Utilizing Lorentz transmission electron microscopy (LTEM) for the first time in this context, we have visualized and analyzed the domain walls in such ultra-thin amorphous wires. All the investigated samples display vortex magnetic domain walls, regardless of wire composition or diameter. In non-magnetostrictive wires, the domain walls maintain their structure and symmetry under varying magnetic field conditions. In contrast, magnetostrictive wires show an elongation of their domain walls upon magnetic field application, a response linked to the magnetoelastic coupling between magnetostriction and internal stresses induced during wire preparation. This study advances the understanding of magnetization reversal processes in amorphous submicronic wires. The insights gained are crucial for future developments in miniaturized magnetic devices.

A Curvature Sensor Utilizing the Matteucci Effect in Amorphous Wire.

The study of wearable sensors for human disease monitoring has developed into an important research area due to its potential for personalized health care. Various sensor types have been proposed for assessing the range of joint movement in patients with progressive diseases or following post-surgical treatments. Many of these methods suffer from poor accuracy, sensitivity, and linearity or are very expensive and complex to implement. To overcome some of these limitations, this paper reports on the development of a novel flexible sensor for the measurement of bending by utilizing the Matteucci effect in the amorphous wire. This paper describes a bend sensor that utilizes positive magnetostrictive amorphous wire to achieve a measurement sensitivity equal to 5.68 ± 0.02 mV/cm with a resolution of ±0.2° over a measuring range of 64 to 143°.

Magnetostrictive Materials for aerospace applications

Structural health monitoring of composite structures to detect barely visible damage is vitally important for the aerospace industry. This research has investigated amorphous magnetostrictive wires (Fe77.5Si7.5B15 and Co72.5Si12.5B15), as a possible solution to monitoring aerospace composites. The different amorphous wires were either embedded into the composite or epoxied on to the surface. How the wires effected the structure of the composite along with ultimate tensile strength was studied. Inductance measurements were used to study the strain within the composite, which provided a non-intrusive method of monitoring the composite.

A wearable magnetic sensing device for identifying the presence of static magnetic fields

Nowadays, the ever growing use of electronic equipment in everyday life raises issues regarding the safety of specific population groups, such as patients carrying EMI sensitive implantable devices (e.g. cardiac pacemakers, surgical stents, etc.). In this respect, the need for wearable magnetic monitoring systems, able of detecting the presence of possibly hazardous magnetic fields of various different origins may become obvious. In this work, a wearable magnetic sensing device has been constructed in order to assess its ability to identify the presence of static magnetic fields of magnetic flux density up to 6 Gauss. Magnetostrictive delay lines (MDLs) have been employed as the sensing elements, due to their fibrous form and minimal thickness, which allows integration in textile and clothing products. Two different amorphous magnetostrictive materials, in ribbon and wire form respectively, have been tested in order to reveal the most appropriate solution for the application under consideration. Moreover, different performance aspects, such as uniformity of sensor’s response as well as temperature effects have been examined. The experimental results indicate that the proposed system can effectively operate within the required magnetic flux density range. Moreover, the fibrous character of the MDL makes it a perfectly suitable material for wearable applications.

ChemInform Abstract: Novel Trends in the Study of Magnetically Soft Co‐Based Amorphous Glass‐Coated Wires

AbstractReview: 38 refs.

Investigation of Strain Sensing Capabilities of Amorphous Magnetostrictive Wires Embedded in Epoxy Resin

The development of fibers and adhesive systems with high durability has recently led to the creation of a new repair method of metallic structures, by the use of reinforcing patches made of composite materials. This technique is generally reported as "Composite patch repair" and provides very important advantages compared to the conventional methods of repairs. On the other hand, the technology of induction heating constitutes an innovative approach to achieve the supply of energy for the curing of resins or for the manufacturing of composite materials. In the case of resins, a ferromagnetic material must be imported into the resin, to produce the required heat. This may be achieved by importing a metallic grid in the resin. Moreover, this metallic grid, which remains inside the resin after the curing, may serve as sensor by analyzing its electrostatic properties, thus providing useful information about the structural integrity of the area (e.g. potential increase of the crack below a bonded composite repair). In this paper we present results concerning the strain sensing capabilities of amorphous magnetostrictive wires embedded in epoxy resin. The inverse magnetostrictive effect leads to a change of permeability of wires so that applied stress can change the impedance of the amorphous wires due to the skin effect with alternating current excitation. Two different types of sensing were used, contact sensing (attachment of the wire “gauge” to a sensing devise) and induction sensing (eddy current sensing probe).

Comparative study of the magnetic properties of positive and nearly zero magnetostrictive submicron amorphous wires

Rapidly solidified submicron amorphous wires with positive and nearly zero magnetostriction are studied in order to understand the effect that a significant reduction in the diameter of the metallic nucleus has on their magnetic behavior and anisotropy distribution. Submicron wires with metallic nucleus diameters between 350 and 800 nm were investigated with hysteresis loop measurements, the magneto-optical Kerr effect, and ferromagnetic resonance studies. The analysis of the results shows the dominant role of shape anisotropy in nearly zero magnetostrictive submicron wires, as well as in positive magnetostrictive ones with nucleus diameters smaller than 350 nm. Magnetoelastic anisotropy is still important in positive magnetostrictive submicron wires with metallic nucleus diameters larger than 500 nm.

Magnetoimpedance in soft magnetic amorphous and nanostructured wires

The surface impedance tensor approach has been used to review the impedance response in a variety of amorphous and nanocrystallized wires. An experimental study on the torsion annealing effect on the magnetoimpedance (MI) behaviour for positive and negative magnetostriction amorphous wires of FeSiB and CoSiB compositions, respectively, has been carried out. Moreover, the influence of the onset nanocrystallization on the MI behaviour in Finemet-type alloys, with particular attention focussed on the case that the wires are annealed under applied torsional stress, is also presented. The analysis of the MI and torsion-impedance (TI) effects allows us to compare the different magnetic characteristics observed in a variety of wires. Special attention is paid to new results of the off-diagonal MI huge responses of these ferromagnetic samples, which are also a very useful source of information on the magnetic properties of the wires.

Magnetic behavior of rapidly quenched submicron amorphous wires

Results on the magnetic behavior of glass-coated amorphous wires with metallic nucleus diameters in the submicron range are reported for the first time. The magnetic behavior of nearly zero magnetostrictive submicron amorphous wires is different from that observed in amorphous microwires with typical dimensions and similar composition. Submicron wires are bistable, whereas typical microwires show an almost anhysteretic loop. Bistability of submicron wires is maintained even in a very thin surface layer, which was shown to display a helical magnetic anisotropy. The origin of this specific behavior is the shape anisotropy which becomes dominant at lower dimensions of the metallic nucleus. The study of submicron amorphous wires opens up the way for new applications of amorphous wires.

Transformation of surface domain structure in Co-rich amorphous wires

The process of magnetization reversal in Co-rich nearly zero magnetostrictive amorphous wire having circumferential magnetic anisotropy in the outer shell has been studied. The investigations have been performed using magneto-optical Kerr effect microscope. The main regularities of the domain structure transformation have been elucidated. The nucleation and the movement of the domain wall and magnetic vortexes are the basic components of the magnetization reversal determined the value of the giant magneto-impedance effect in these wires.

Dynamic magnetization processes in magnetostrictive amorphous wires

We have performed the theoretical studies on the longitudinal dynamic magnetization process of magnetostrictive amorphous wires characterized by a large single Barkhausen jump (magnetic bistability) based on our previous experimental measurements on these wires. The domain structures of these wire samples consist of a single domain inner core with axial magnetization surrounded by the outer domain shell with the magnetization oriented perpendicular (λs>0) or circular (λs<0) to the wire axis. In the present work we use the resultant magnetization vector M⃗ tilting θ angle to z axis to describe the sample’s domain structures. In terms of solving the Landau-Lifshitz-Gilbert equation followed by M⃗ the analytical solution of the dimensionless axial component of the magnetization mz=MZ∕Ms has been obtained, and mz[t(H0,fe),τ,γ] is a function of the field amplitude H0, field frequency fe, and the samples’ material parameters such as the damping constant τ and the gyromagnetic ratio γ. The function mz[t(H0,fe),τ,γ] allows us to study the dynamic properties of the magnetization process of a wire sample. It has been found that the switching time ts, the switching field Hsw, and the dynamic coercive field Hdc depend on a magnetic field and material parameters. We found that the parameter α=γτ∕(1+τ2) related to the rate of M⃗, rotating the direction of the effective field, plays an important role in the magnetization process. By fitting the experimental data to the theoretical magnetization curve the value of the damping constant τ of the magnetostrictive amorphous wires can be estimated.

The effect of magnetoelastic interaction on the GMI behaviour of Fe-, Co- and Co–Fe-based amorphous wires

The giant magnetoimpedance is the sensitive change in ac impedance value with the application of dc magnetic field when ac current passes through the sample. In the present work GMI properties of positive (Fe 77.5Si 7.5B 15), negative (Co 72.5Si 12.5B 15) and nearly zero ((Co 94Fe 6) 72.5Si 12.5B 15) magnetostrictive amorphous wires have been studied. The result indicates that the magnetostriction constant plays an important role in GMI property. The maximum GMI ratio (330%) and maximum field sensitivity (7% per A/m) are observed in (Co 94Fe 6) 72.5Si 12.5B 15 amorphous wire. The frequency response of the GMI characteristics of the above alloys has been measured and zero magnetostrictive (Co 94Fe 6) 72.5Si 12.5B 15 material showed better frequency response.

Security Sensor System Based on Large Barkhausen Jump of Amorphous Magnetostrictive Metal Wires

This paper presents and discusses preliminary laboratory results for fabrication and testing of a security sensor system for use in article surveillance in such places as libraries, CD rental shops, and supermarkets, as a crime preventive measure. The system employs the large Barkhausen jump (LBJ) inherent in the amorphous magnetostrictive metal wires. The system takes advantage of the superior sensor characteristics of magnetostrictive metal wires. Journal of Agriculture, Science and Technology Vol.4(1) 2002: 91-101

Low-frequency circumferential magnetization curves in magnetostrictive amorphous wires

Circumferential magnetization curves have been derived from the imaginary component of the impedance response in an Fe 73.5Si 13.5B 9Cu 1Nb 3 amorphous wire. Measurements were performed at 1 kHz driving frequency, and 0.05– 20 mA rms current amplitude range. Axial DC fields from 0 to 100 Oe have been simultaneously applied in order to detect the magnetoinductive effect. The circular magnetization curves are compared with quasi-static longitudinal magnetization ones, and the results are analyzed on the basis of the core-shell model for a wire with positive magnetostriction.

The effect of furnace annealing and surface crystallization on the anisotropy, ΔE and magnetoimpedance effects in Fe71Cr7Si9B13 amorphous wires

The dependence of the magnetization loops, coercivity, anisotropy constant, ΔE and magnetoimpedance (MI) effects in positively magnetostrictive Fe71Cr7Si9B13 amorphous wires on annealing conditions were studied. Samples were annealed at temperatures of 440°C and 460°C for durations between 0.3 and 300 min. The results indicate that progressive annealing first leads to relief of internal stresses and annealing of wires at 460°C for 60 min produces the minimum coercivity of about 1 A m−1. Further annealing increases the coercivity and anisotropy, due to partial crystallization at the surface. It was found that the anisotropy changes its direction to the circumferential direction with the surface crystallization. The maximum change in Young's modulus was measured to be about 75% in a partly surface crystalline sample. It was observed that the magnitude of the MI effect of the stress relieved sample could exceed 200% at 1 MHz.

Fiber-optic extrinsic Fabry-Perot dc magnetic field sensor.

We demonstrate a compact extrinsic Fabry-Perot interferometer-based fiber-optic sensor that uses magnetostrictive amorphous metallic wire Unitika AF-10 (Fe77.5B15Si7.5) as a sensor gauge for measuring dc magnetic fields. We present a theoretical model based on a Gaussian electric field distribution to analyze the sensor operation as a function of longitudinal air-gap separation. The model shows good agreement with the experimental results. A resolution of 50 nT over a range of 50-40,000 nT with a simple passive temperature-compensation method is obtained.

Dynamic circular hysteresis in Co-based amorphous microwires

Abstract The circular hysteresis loops in CoFeSiB negative magnetostrictive amorphous wires with glass cover have been measured at frequencies up to 250 kHz under the effect of axial DC magnetic field. The loops are partitioned into reversible and irreversible portions assigning them corresponding permeability parameters. It is demonstrated that the introduced permeabilities are characterised by different field-frequency behaviour. This analysis is helpful to understand the variety of magnetoimpedance characteristics reported for different frequency ranges and excitation conditions.

Optimum driving of magnetostrictive amorphous wire micro-motor

Abstract Characteristics of a magnetostrictive vibration micro-motor were investigated in relation to a supporting position of a magnetostrictive amorphous wire for optimization of the motor. It was found that a vibration of the wire resembled a vibration mode of both ends free and a maximum rotational speed was obtained by supporting the nodes of vibration.

Correlation between magnetoelastic resonance and ac field-induced rotation of magnetostrictive amorphous wire

The influence of magnetoelastic resonance in rotation of FeSiB conventional amorphous wires under an axially applied ac field is investigated.

Stress and field dependence of the giant magnetoimpedance effect in Co-rich amorphous wires

Abstract The impedance of nearly zero magnetostriction amorphous wires (Co 68.1 Fe 4.4 Si 12.5 B 15 , λ s =−4×10 −8 ) has been measured as a function of an applied dc longitudinal field, circular driving field frequency and tensile stress. Giant magnetoimpedance (GMI) ratios up to 330% were observed in the lower magnetostriction wire (for frequency f =1 MHz).