Ferromagnetic Glass-coated Microwires Research Articles

An Indirect Method of Micromagnetic Structure Estimation in Microwires.

The tunable magnetic properties of amorphous ferromagnetic glass-coated microwires make them suitable for a wide range of applications. Accurate knowledge of the micromagnetic structure is highly desirable since it affects almost all magnetic properties. To select an appropriate wire-sample for a specific application, a deeper understanding of the magnetization reversal process is required, because it determines the measurable response (such as induced voltage waveform and its spectrum). However, the experimental observation of micromagnetic structure of micro-scale amorphous objects has strict size limitations. In this work we proposed a novel experimental technique for evaluating the microstructural characteristics of glass-coated microwires. The cross-sectional permeability distribution in the sample was obtained from impedance measurements at different frequencies. This distribution enables estimation of the prevailing anisotropy in the local region of the wire cross-section. The results obtained were compared with the findings of magnetostatic measurements and remanent state analysis. The advantages and limitations of the methods were discussed.

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.

Ferromagnetic Glass-Coated Microwires for Electromagnetic Shielding for Medical Application

Ferromagnetic Glass-Coated Microwires for Electromagnetic Shielding for Medical Application

Influence of Technological Parameters on Magnetic Properties of Co-Rich Amorphous Ferromagnetic Microwires

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Ferromagnetic glass-coated microwires with good heating properties for magnetic hyperthermia.

The heating properties of Fe71.7Si11B13.4Nb3Ni0.9 amorphous glass-coated microwires are explored for prospective applications in magnetic hyperthermia. We show that a single 5 mm long wire is able to produce a sufficient amount of heat, with the specific loss power (SLP) reaching a value as high as 521 W/g for an AC field of 700 Oe and a frequency of 310 kHz. The large SLP is attributed to the rectangular hysteresis loop resulting from a peculiar domain structure of the microwire. For an array of parallel microwires, we have observed an SLP improvement by one order of magnitude; 950 W/g for an AC field of 700 Oe. The magnetostatic interaction strength essential in the array of wires can be manipulated by varying the distance between the wires, showing a decreasing trend in SLP with increasing wire separation. The largest SLP is obtained when the wires are aligned along the direction of the AC field. The origin of the large SLP and relevant heating mechanisms are discussed.

Engineering of giant magnetoimpedance effect of amorphous and nanocrystalline microwires

We present our studies of the factors affecting soft magnetic properties and giant magnetoimpedance effect in thin amorphous and nanocrystalline microwires. We showed that the magnetoelastic anisotropy is one of the most important parameters that determine magnetic softness and GMI effect of glass-coated microwires and annealing can be very effective for manipulation the magnetic properties of amorphous ferromagnetic glass-coated microwires. Considerable magnetic softening and increasing of the GMI effect is observed in Fe-rich nanocrystalline FINEMET-type glass-coated microwires after the nanocrystallization.

Engineering of Giant Magnetoimpedance Effect of Amorphous and Nanocrystalline Microwires

We present an overview of the factors affecting soft magnetic properties and giant magnetoimpedance (GMI) effect of thin amorphous wires. Low coercivity and high GMI effect have been observed in as-prepared Co-rich microwires. We showed that the magnetoelastic anisotropy is one of the most important parameters that determines the magnetic softness and GMI effect of glass-coated microwires, and annealing can be very effective for manipulation of the magnetic properties of amorphous ferromagnetic glass-coated microwires. After annealing of Co-rich microwires, we can observe the transformation of inclined hysteresis loops to rectangle and coexistence of fast magnetization switching and GMI effect in the same sample. We demonstrated that the switching field value of microwires can be tailored by annealing in the range from 4 to 200 A/m. On the other hand in Fe-rich FeCuNbSiB microwires after appropriate annealing, we observed considerable magnetic softening and GMI effect enhancement.

Tailoring of Magnetic Properties and Magnetoimpedance Effect in Thin Amorphous Wires

We have studied the effect of annealing conditions on magnetic properties of amorphous CoFeNi-based glasscoated microwires. We show that annealing can be very effective for manipulation the magnetic properties of amorphous ferromagnetic glass-coated microwires. Low coercivity and high giant magnetoimpedance (GMI) effect have been observed in as-prepared Co-rich microwires. After annealing of Co-rich microwires we can observe transformation of inclined hysteresis loops into rectangular and coexistence of fast magnetization switching and GMI effect in the same sample. We demonstrate that the switching field value of microwires can be tailored by annealing in the range from 4 to 200 A/m.

Engineering of magnetic properties and GMI effect in Co-rich amorphous microwires

We studied the effect of annealing conditions on magnetic properties of amorphous CoFeNi-based glass-coated microwires. We showed that annealing can be very effective for manipulation of the magnetic properties of amorphous ferromagnetic glass-coated microwires. Low coercivity and high Gaint magnetoimpedance (GMI) effect have been observed in as-prepared Co-rich microwires. After annealing of Co-rich we can observe transformation of linear hysteresis loops to rectangular and coexistence of fast magnetization switching and GMI effect in the same sample. We demonstrated that the coercivity of microwires can be tailored by annealing in the range from 4 to 200 A/m. We found that the annealing considerably affects the magnetostriction coefficient and observed correlation between the magnetic hardening of studied microwires and the magnetostriction sign change.

Domain Wall Propagation in Co-Based Glass-Coated Microwires: Effect of Stress Annealing and Tensile Applied Stresses

RECENTLY, domain wall (DW) propagation in magnetic wires has been recognized as one of the important lines of research due to its potential use in magnetic devices [1]–[7]. The DW speed and the possibilities for the DW dynamics manipulation are quite relevant for these applications. Extremely fast DW propagation has been reported for amorphous magnetically bistable microwires with positive magnetostriction constant λs and circular cross section (usually, exceeding 1000 m/s) [3], [4]. On the other hand, ferromagnetic glass-coated microwires have attracted growing attention in the last few years, mostly owing to their outstanding soft magnetic properties (magnetic bistability, enhanced magnetic softness, Giant magnetoimpedance (GMI) effect, and fast DW propagation) [5]–[7]. These microwires have a composite character consisting of a cylindrical metallic nucleus of (1–30 μm) and glass coating (with thickness of 1–20 μm). These microwires can be prepared by the modified Taylor–Ulitvosky technique, which involves simultaneous rapid quenching and drawing of the metallic nucleus inside a glass capillary [6], [7]. Thus, strong stresses are introduced in the metallic nucleus arising from the drawing and quenching, as well as from the different thermal expansion coefficient between the glass sheath and the metallic nucleus [5], [6], [8]–[10]. Therefore, the magnetoelastic anisotropy induced by the internal stresses plays an important role in controlling their magnetic properties [4], [5], [7]–[9]. Fe-rich microwires with positive magnetostriction coefficient, λs , present magnetic bistability related to a large and single axially magnetized inner core. Therefore, one can observe quite fast magnetization switching within the single magnetic domain related with fast DW propagation. In particular, these materials are unique for studying the DW propagation since they can exhibit a very fast DW velocity [2]–[4], [6], [11]. On the other hand, it is well known that the DW dynamics in glasscoated microwires is strongly dependent to external parameters

Sensing RF and microwave energy with fiber Bragg grating heating via soft ferromagnetic glass-coated microwires

We present results from a fiber Bragg grating-based microwave energy sensor. The sensor relies on a soft ferromagnetic glass-coated microwire that is bonded to the cladding of the grating. The microwire absorbs microwave energy and heats up thus raising the temperature of the fiber Bragg grating. Compared to a similar sensor that uses gold to absorb electromagnetic radiation, the microwire yields a sensor with greater sensitivity (∼10 times at f=3.25GHz) relative to the perturbation of the microwave field. With the sensor reported here, the best sensitivity to electromagnetic radiation corresponds to AC electric fields that have an average electric energy density of approximately 1.3μJ/m3.

Interaction of bistable glass-coated microwires in different positional relationship

The amorphous ferromagnetic glass-coated microwires with positive magnetostriction constant of the metallic core possess the bistable magnetization reversal and the fast domain wall propagation along the microwire axis. These properties and also the magnetization processes in the systems of the microwires are of interest in the magnetic sensing technology, encoding systems and smart composite applications. In this work we present the results of the experimental investigation, simulations and theoretical estimations of the hysteresis process in the systems of the magnetically bistable microwires with different length and positional relationship between them. The location of the short microwires near the long microwire affects the switching fields (external coaxial magnetic field applied for starting of the domain wall propagation along the microwire axis) and the hysteresis process. The changes of these properties are not directly proportional to the value of the shorter microwire shift along the longer one. When the short microwire was placed in the middle of the long one and when the one end of the long microwire coincided with the end of the short one, the two-steps hysteresis loops were observed for both sample orientations: before and after sample rotation on 180°. When the short microwire was placed close to the end of the long microwire (but did not coincide with it) we observed at first the two-steps hysteresis loop and single step behavior for one branch of the hysteresis loop after sample rotation. Moreover, changing of the orientation of the samples results in the shift of the switching field of the shorter microwire when its end was located near the end or coincided with the end of the longer one. This uncommon hysteresis behavior was explained and illustrated using results of the simulations. The values of microwires interaction were also estimated.

Surface Magnetization Processes in Amorphous Microwires

Surface magnetization processes in ferromagnetic glass-coated amorphous microwires with positive, negative, and nearly zero magnetostriction have been investigated. The results indicate helical magnetization in the surface region of positive magnetostrictive microwires and enhanced soft magnetic properties on the axial direction. The typical bistable behavior of such microwires is maintained within the surface region. Nearly zero magnetostrictive microwires with diameters larger than 20 ¿m also display bistability in the surface region, whilst negative magnetostrictive ones are not bistable. The values of the metallic nucleus diameter and glass coating thickness affect the surface magnetoelastic anisotropy, as emphasized by the changes in the values of the axial and transverse switching fields. The obtained results are important for a better understanding and control over the surface magnetization processes for high frequency applications of amorphous microwires.

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We studied the effect of annealing conditions on magnetic properties of amorphous CoFeNi-based glass-coated microwires. We showed that annealing can be very effective for manipulation of the magnetic properties of amorphous ferromagnetic glass-coated microwires. Low coercivity and high Gaint magnetoimpedance (GMI) effect have been observed in as-prepared Co-rich microwires. After annealing of Co-rich we can observe transformation of linear hysteresis loops to rectangular and coexistence of fast magnetization switching and GMI effect in the same sample. We demonstrated that the coercivity of microwires can be tailored by annealing in the range from 4 to 200 A/m. We found that the annealing considerably affects the magnetostriction coefficient and observed correlation between the magnetic hardening of studied microwires and the magnetostriction sign change.

Static and Dynamic Properties of Fe-Si-B-Nb-Cu Nanocrystallized Ferromagnetic Glass-Coated Microwires From 20$^circ$C to 350$^circ$C

In this paper, nanocrystallized glass coated microwires have been elaborated. Their magnetic properties have been determined and compared to amorphous Co-based microwires. We studied two alloys in the Finemet family and two geometries of microwires. We observed a dependence of the magnetic anisotropy with both the composition and the diameters of the microwires. We also performed permeability measurement in the 200 MHz to 4 GHz range up to 350degC. We report a fair stability of the microwave properties, and also their reversible behavior. These properties are very attractive for high frequency high temperature applications. This contrasts with Co-based microwires that exhibit poor thermal stability. The origin of the anisotropy in nanocrystallized microwires is discussed

Microwave permeability of metamaterials based on ferromagnetic composites

In this paper, we focus on metamaterials based on ferromagnetic composite combined with an inductive pattern. CoFeSiB amorphous ferromagnetic glass-coated microwires and thin films are involved in the composite. The inductive pattern is a coiling of Copper wire with a varying number of loops. We derived the microwave permeability of the ferromagnetic material inside the inductive pattern through a Landau–Gilbert model of gyromagnetism. In agreement with experimental results, the engineering of resonance frequency of the sample is achieved through the number of loops of the coiling.

Magneto-elastic anisotropy of ferromagnetic glass-coated microwires

Abstract One of the interests of ferromagnetic glass-coated microwires is the possibility to engineer their anisotropy thanks to magneto-elastic effects. In this paper, we focus on the link between the stress models that have been established for these materials and the magneto-elastic behavior. We use the hysteresis loops under stress of microwires to determine their magneto-elastic properties. We compare the experimental magnetic anisotropy of many samples with different metallic core diameter and glass thickness with the magnetic anisotropy estimated using the magneto-striction coefficient and the total stress in the microwires: internal stress (coming from the elaboration process) and external stress (applied during the measurement).

Microwave permeability of amorphous ferromagnetic glass-coated microwires from 150 K to 450 K

Microwave permeability spectra of ferromagnetic glass-coated microwires at room temperature have already been studied. Using a new setup that we have recently developed, permeability spectra of ferromagnetic microwire at various temperatures are presented. CoFeSiB soft ferromagnetic microwires are studied from 150 K to 450 K, showing large changes in their permeabilities between 30 MHz and 3 GHz.

Interaction between Fe-rich ferromagnetic glass-coated microwires

Hysteresis loop measurements of several Fe-rich glass-coated amorphous microwires of Fe 65Si 15B 15C 5 composition have been performed using the conventional fluxmetric and SQUID magnetometers and magneto-optical Kerr effect technique. The number of the wires used in the measurements has been varied from 1 to 10. The hysteresis loops exhibit large Barkhausen jumps (LBJ) between two remanent states for all number of the wires involved in the measurements. The number of jumps is correlated with the number of wires. The lowest switching field decreases as the number of wires increases. The shape of the hysteresis loop and the switching field values depend on the sweeping rate, d H/d t, and on the distance between wires. The obtained results have been analyzed considering the mutual influence of the wires due to stray field effects. The superposition of external and stray fields creates some spatial distribution of the magnetic field to produce successive magnetization reversals in the multi-wire system.