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Magnetic anisotropy and stress-magnetoimpedance (S-MI) in current-annealed Co-rich glass-coated microwires with positive magnetostriction
Abstract
Effects of a dc current annealing, in terms of magnitude and inflow time, on magnetic hysteresis properties, magnetoimpedance (MI) and stress-magnetoimpedance (S-MI) in glass-coated amorphous Co71Fe5B11Si10Cr3 microwires with a small positive magnetostriction were investigated in this work. The annealing process combining Joule-heating and circular magnetic field leads to the creation of a specific magnetic anisotropy of a helical or circular type, and consequently, is helpful to control the MI and S-MI behaviours making them more suitable for particular sensing applications. After annealing, the magnetoimpedance plots transformed from a bell-shaped typical of an axial easy anisotropy to the shape with two symmetrical peaks, the magnitude and position of which are controlled with the annealing current parameters. Applying a tensile stress on the annealed wires changes the easy anisotropy direction which leads to the potential for highly sensitive S-MI without use of dc bias fields. A stress sensitivity of more than 260 % at σex=250 MPa at zero magnetic field is achieved.
... Furthermore, the hysteresis loops of as-cast and modified GCM were shown in Fig. 4a. The loop of as-cast GCM exhibits inclining shape with low coercivity and large susceptibility, implying that the wire has circumferential or helical anisotropy [25,26]. The shape of hysteresis loops did not considerably change after the modification of APTES solution. ...
... Certainly, these changes can also be derived from the interfacial stresses formed by other treatment agents or curing shrinkage. Thus, it is demonstrated that the impedance of GCM is extremely sensitive to the external stress field, including the tensile stress that have been reported [18,26] and the interfacial stress in this work. ...
... As mentioned above, GCM-3 has high-sensitivity of interfacial stress owing to their well-defined circumferential/helical anisotropy induced by surfactant layer [18,26]. For the microwire with tinier resin microdroplet, the impedance significantly increased due to helical anisotropy by interfacial stress [33]. ...
A new rapid evaluation method of composite interfacial shear strength (IFSS) on basis of impedance parameter utilizing the glass-coated cobalt-based ferromagnetic microwire (GCM) with sensitive stress-impedance effect is proposed. The intrinsic properties analysis and surface modification of GCM were performed to improve the sensitivity of stress-impedance effect and meet the application requirements in composites. The correlation between impedance increments and interfacial stress is investigated for GCM composites with different resin embedded length through experimental verification and finite element simulation. The impedance increment of microwire shows a high degree of dependence on IFSS of GCM/resin systems, which is mainly associated with local interfacial stress from the resin. Based on this correlation mechanism and IFSS measured by microdroplet debonding test, IFSS of composites with different resin matrix were successfully calculated from impedance parameter, and the interfacial bonding of resin matrix could be distinguished and sorted as relatively superior or inferior conveniently and rapidly. Comparing with sophisticated, lengthy and expensive interface mechanical tests after the manufacture of fibers and resin, the pre-use efficient interfacial assessing of resin matrixes only using GCM shows more necessary and potential to screen resin matrix with excellent interfacial properties towards advanced fiber-reinforced thermosetting resin matrix composite.
... Application magnetic glass-coated cast amorphous micro and nanowires (GCAMNWs) is considered also in articles [1][2][3][4]. The properties of the magnetic glass-coated cast amorphous micro and nanowires studies in many publications by various research groups [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. ...
... Another principle of detecting mechanical strain is examined in [15,16]. This principle is based on the giant magnetoimpedance (GMI) effect. ...
... This principle is based on the giant magnetoimpedance (GMI) effect. The GMI effect [15,16] demands external magnetization of the sample which is not required in the NFMR method [6][7][8][9]. ...
... The absorption of composite materials in the form of screens with built-in segments of GCAMNW have been experimentally investigated. Theoretical studies have also been carried out, which have shown that a significant proportion of the absorption can also be due to geometric resonance [3,4,[7][8][9][10]. The greatest effect is expected for nanowires with a core radius comparable with the thickness of the skin layer. ...
... Scientific literature presents the results of simultaneous research of the use of giant magnetic impedance (GMI) to measure such SEs (see, for example [8]). However, the use of the GMI effect does not seem to be technological (this issue has already been covered in [7]) and will not be considered in this paper. ...
The paper analyzes technological aspects of the Taylor–Ulitovsky method used to produce microwires of various structures. Natural ferromagnetic resonance (NFMR) in cast glass-coated amorphous magnetic micro- and nanowires was theoretically and experimentally studied. The NFMR phenomenon is due to the large residual stresses appearing in the core of the microwire during the casting process. These stresses, along with magnetostriction, determine magnetoelastic anisotropy. Besides residual stresses, the NFMR frequency is influenced by externally applied stresses on the microwire or the composite containing the so-called stress effect (SE). The dependence of the NFMR frequency on the deformation of microwires and the external stresses on them is proposed to be used for remote diagnostics in medicine
... The cast GCAMNWs are manufactured by means of a modi ied Taylor-Ulitovsky process [2][3][4]. The preparation of microwires and studies of the magnetic properties were reported in many publications by various research groups [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19]. ...
... It is well known that a large percentage of the destruction and resulting victims of earthquakes occur during repeated aftershocks of the earth's crust which are weaker than the primary tremors. However, no information on the implementation of such a control method has been published, although recent research in the ield of NFRM in microwires has become more intense [4,[6][7][8][9][10][11][12][13]19]. ...
... Amorphous alloys based on 3D metals produced in the form of ribbons and wires are excellent soft magnetic materials used in a large number of applications, including sensors [1][2][3][4]. The choice of composition depends on a particular application, but generally, the alloy includes (Fe,Co,Ni) [70][71][72][73][74][75][76][77][78][79][80][81][82][83][84][85] (Si,B) [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30] where the metalloids Si and B help glass formation [5]. The addition of other elements is also used, such as, for example, Cr and Mo to stabilize the amorphous structure [6][7][8][9]. ...
... Simultaneously, the internal stress frozen-in during fabrication is relaxed, which eliminates the temperature instability. For example, the current annealing of amorphous wires of Co-rich compositions with moderate current intensities induces a circumferential easy anisotropy and positive magnetostriction [24,28,29]. The application of tensile stress along the wire contributes to long-range axial anisotropy and strongly affects the remagnetization process and magnetoimpedance. ...
Amorphous ferromagnetic materials in the form of microwires are of interest for the development of various sensors. This paper analyzes and argues for the use of microwires of two basic compositions of Co71Fe5B11Si10Cr3 and Fe3.9(4.9)Co64.82B10.2Si12Cr9(8)Mo0.08 as stress/strain and temperature sensors, respectively. The following properties make them suitable for innovative applications: miniature dimensions, small coercivity, low anisotropy and magnetostriction, tunable magnetic structure, magnetic anisotropy, and Curie temperature by annealing. For example, these sensors can be used for testing the internal stress/strain condition of polymer composite materials and controlling the temperature of hypothermia treatments. The sensing operation is based on the two fundamental effects: the generation of higher frequency harmonics of the voltage pulse induced during remagnetization in wires demonstrating magnetic bistability, and magnetoimpedance.
... In the case of microwires with a metallic core diameter in the range of 20 μm, currents of 25-50 mA correspond to temperatures of 400-550 K which are high enough for structural relaxation and partial relief of internal stresses [18], but lower than the crystallization temperature T x of 720 K shown in Fig. 3 a. DSC curves of the as-cast wires and 30 mA and 40 mA annealed wires reveal the influence of current annealing on the structural relaxation and crystallization processes. ...
... Fig. 6 shows the magnetic hysteresis loops (Fig. 6 a) and the magnetic field dependence of the magneto-impedance (MI) ratio for the as-cast and annealed samples annealed with different currents (Fig. 6 b). Both the magnetization process and magneto-impedance ratio of microwires are defined by the magnetic anisotropy, which can be affected e.g. by current annealing [18,22]. Large internal stresses give rise to a large anisotropy, which is evidenced in the M-H loop of the as-cast wire (Fig. 6 a). ...
... In order to check the effect of annealing treatment on the structural and thermal properties of the microwires, we explored DSC and XRD analyses. In the case of microwires with a metallic core diameter in the range of 20 microns, currents of 25-50 mA correspond to temperatures of 400-550 K which are high enough for structural relaxation and partial relief of internal stresses [11], but lower than the crystallization temperature, Tc of 720 K shown in Fig. 3 a. In addition, the microwires are still magnetic in that range of temperature as evidenced by the Curie temperature, Tc of 630 K. ...
... [ Figure 5 here] Figure 6 shows the magnetic hysteresis loops (Fig. 6 a) and the magnetic field dependence of the magneto-impedance ratio for the as-cast and annealed samples annealed with different currents (Fig. 6 b). Both the magnetization process and magneto-impedance ratio of microwires are defined by the magnetic anisotropy affected e.g. by current annealing [11,13]. ...
Traditional approaches to realize microwave tunability in microwire polymer composites which mainly rely on topological factors, magnetic field/stress stimuli, and hybridization prove to be burdensome and restricted to rather narrow band frequencies. This work presents a novel yet facile strategy based on a single component tunable medium to program the transmission response over wide frequency bands. To this end, we demonstrated that structural modification of one type of microwire through suitable current annealing and arrangement of the annealed wires in multiple combinations were sufficient to distinctly red-shift the transmission dip frequency of the composites. Such one wire control-strategy endorsed a programmable multivariable system grounded on the variations in both the overall array conductivity or "effectiv" area determined by the wires arrangement and the relaxation time dictated by the annealing degree of microwires. These results can be used to prescribe transmission frequency bands of desired features via diverse microwire arrays and microwave performance from a single component to a composite system design.
... The electromagnetic properties at the microwave frequency of these meta-composites dependent on the external stress field and matrix damage, among others, are of considerable interest from the SHM application point of view [22,23], nevertheless, their application scenarios are limited due to electromagnetic shielding effect of carbon fiber reinforced composites. Thus, research efforts are switched to how to develop the intrinsic stress-sensitive magnetic and impedance properties of MFs [24,25]. The magnetic parameters (such as coercivity, and anisotropy field) of MFs extracted from the hysteresis loop can directly reflect the stress state, but their complicated measurement compromises these advantages [26]. ...
Multifunctional composites realized by embedded sensing materials draw much attention to structural health
monitoring applications. However, conventional composites are not able to recognize their strain behavior,
meanwhile, the embedded sensing elements lack compatibility with host structures and inevitably cause the
degradation of the properties. Herein, flexible and micro magnetic fibers (MFs) as embedded sensing units enable
conventional composites to possess intelligent self-sensing ability. Combining impedance measurement with
mechanical test, the sensing mechanism of MFs is elucidated that the stress-sensitivity of MFs derives from the
natural ferromagnetic resonance induced by its intrinsic magnetic anisotropy. The uniaxial tensile and cyclic
loading are executed to investigate the electromechanical response ability and monitoring stability of MF
monofilament as a sensing element. Then, MFs are embedded into glass fiber (GF) reinforced composites to
realize multi-functional MF/GF composites with self-sensing capability, which also do not deteriorate their
original mechanical properties. The MF/GF composites inherit high strain sensitivity with a maximum gauge
factor of 376, and simultaneously exhibit the ability of bending orientation recognition and damage detection.
The MF as a low invasive and embedded functional fiber has great potential to realize self-sensing ability of fiber reinforced composites, which find particular priority application in pressure vessels and pipes.
... cally have a combination of a circumferential anisotropy and negative magnetostriction or an axial anisotropy and positive magnetostriction [11,13,14]. The possibility of the combinations of a helical anisotropy and positive magnetostriction in Co-based and Fe-based amorphous wires due to current or stress annealing was recently demonstrated [15,16]. Here we aim at the optimization of the current annealing conditions to realize the required magnetic anisotropy and magnetostriction leading to a highly sensitive magnetoimpedance behavior with respect to applied tensile stress. ...
In this paper, the transformation in easy-axis anisotropy and magnetostriction in Co-rich amorphous microwires by dc current annealing has been studied with the aim to realize stress-sensitive magnetization process and magnetoimpedance (MI). With increasing the annealing current intensity Ian, the anisotropy and magnetostriction undergo non-monotonic changes owing to different processes occurring during annealing: structural relaxation, atomic pair ordering, atomic rearrangements, internal stress relief and phase transformation at the crystallization onset. At moderate values of Ian the induced anisotropy sets a near-circumferential easy direction whilst the magnetostriction parameter increases from a very low negative value in the as-cast state to positive values. At optimal combination of the induced anisotropy and positive magnetostriction a highly stress-sensitive MI behavior is observed which is important for stress-sensory applications. At these conditions, the impedance vs. magnetic field plots may change shape in the presence of tensile stress which at zero field is accompanied by a huge impedance change in the range of 70–162% per 100 MPa.
... Further annealing at 40 mA seems to deteriorate the magnetization along the circumference likely 7 due to the above-mentioned onset of crystallization in that sample. Such changes in magnetization and impedance curves are related to relief of internal stresses and structural relaxation [22,23]. Changes in electrical conductivity also reflect the structural modification of the microwires during current annealing (Fig. 3c). ...
Previously, we have shown the advantages of an approach based on microstructural modulation of the functional phase and topology of periodically arranged elements to program wave scattering in ferromagnetic microwire composites. However, the possibility of making full use of composite intrinsic structure was not exploited. In this work, we implement the concept of material plainification by an in-built vertical interface on randomly dispersed short-cut microwire composites allowing the adjustment of electromagnetic properties to a large extent. Such interface was modified through arranging wires of different structures in two separated regions and by enlarging or reducing these regions through wire concentration variations leading to polarization differences across the interface and hence microwave tunability. When the wire concentration was equal in both regions, two well-defined transmission windows with varied amplitude and bandwidth were generated. Wire concentration fluctuations resulted in strong scattering changes ranging from broad passbands to stopbands with pronounced transmission dips, demonstrating the intimate relationship between wire content and space charge variations at the interface. Overall, this study provides a novel method to rationally exploit interfacial effects in microwire composites. Moreover, the advantages of enabling significantly tunable scattering spectra by merely 0.053 vol. % filler loading and relatively simple structure make the proposed composite plainification strategy instrumental to designing microwave filters with broadband frequency selectivity.
... In this case, the annealing temperature should be noticeably lower than the Curie temperature of an amorphous alloy, that is, in the range of 250−300 °C. For the wire core diameter of 25 μm this corresponds to a current of 50−60 mA (or current density of 100-120 A/mm 2 ) [Nematov, Adam 2019]. To crystallize the wire, much higher temperatures (above 500 °C) are needed, which are achieved with currents above 90 mA (or current density above 180 A/mm 2 ). ...
Micro-magnets in the form of a microwire are of interest for various applications including magnetic field bias elements in miniature actuators, sensors, and manipulators. However, a preparation of hard magnetic microwires with sufficiently high magnetization is a difficult task which can be achieved by specific crystallization techniques. Here we propose the current annealing of amorphous microwires as a controllable crystallization technique to convert Co-rich microwire from soft to hard magnetic material. A large increase in coercivity up to 580 Oe is obtained after optimal current annealing (100 mA during 30 - 60 min) which causes crystallization with fine crystal grains of mainly hcp-Co with an average size of 74 nm. We put this forward as a novel technique for micro-magnet fabrication
... This method is based on Joule annealing [7]. It has been proven that the current in an amorphous wire can serve both as a source of heat as well as a source of magnetic field to change the anisotropy direction [8], [9], even if the method was applied on wires with different compositions. The effect of Joule heating on magnetic domain behavior of amorphous wires has been also investigated in [11]. ...
It has been shown that annealing of amorphous magnetic wire used as a core for orthogonal fluxgates in the fundamental mode can significantly decrease the noise of the sensors in the 1/f region. This is due to an increase in the circumferential anisotropy due to the dc current flowing through the wire during annealing. This method, however, presents some drawbacks: first, it requires an infrared furnace and precise compensation of the magnetic field inside it. Second, it is very slow, because it requires the cooling of the whole furnace before removing the wire. Most importantly, while the 1/f noise decreases, the noise floor increases. In this paper, we present a method that allows the simultaneous reduction of 1/f noise and noise floor. This method is based on Joule annealing by means of a very large current in the wire. The current is periodically flipped with 0.25 Hz frequency in order to avoid an excessive increase in the offset. The annealing is performed in a four-layer shielding to avoid the presence of an external dc field. Annealing for 1 min, 1 wire-based sensor returned a considerable noise reduction both in the 1/f regions from 2.5 to 1.5 pT/√ Hz) while the noise floor was unchanged at 650 fT/√ Hz. For larger annealing time, however, the noise floor rose. We tried to compensate this problem by increasing the number of wires to four, but also in this case, we achieved the best noise reduction (from 1.7 to 0.75 pT/√ Hz at 1 Hz and from 470 to 350 fT/√ Hz noise floor) with 1 min annealing. By the use of thermocamera, we discovered that the problem of long-time annealing was that the sensor head support was warming up too much. Therefore, we repeated the experiment by annealing 21 min as a series of 1 min annealing followed by 3 min of no current for 21 times to let the sensor head totally cool to room temperature after every annealing period. In this way, we achieved the lowest noise of 630 fT/√ Hz at 1 Hz and 400 fT/√ Hz noise floor.
The effect of heat treatment of Co-based amorphous microwires at temperatures near the crystallization (Tcr) onset on micromagnetic structure, magnetostriction, and magnetoimpedance (MI) was investigated. As the annealing temperature approaches Tcr, the hysteresis loops abruptly change the shape from almost rectangular to inclined with a small coercivity and remanence magnetization. This behavior is quite unique since even partial crystallization deteriorates soft magnetic properties. The Kerr-microscopy confirmed the formation of a fine circular domain structure and an easy anisotropy direction of a helical type. Both current and furnace annealing with appropriate high temperatures produce similar magnetic transformation. The origin of the formed easy anisotropy is different from that induced by current annealing at temperatures below the Curie temperature and is associated with a change in the magnetostriction constant, which drops from positive to negative values. This could be explained by structural relaxation leading to amorphous phase decomposition at the very initial stage of crystallization. The effect is not specific for the Co-rich alloy composition and was observed in microwires of two compositions: Co71Fe5B11Si10Cr3 and Co66.6Fe4.28B11.51Si14.48Ni1.44Mo1.69 which in the as-prepared state have axial and circumferential anisotropies, respectively. The obtained combination of magnetic anisotropy, magnetostriction and temperature stability leads to useful MI properties, in particular, at Gigahertz frequencies.
Previously, we have demonstrated a viable approach based on microstructural and topological modulation of periodically arranged elements to program wave scattering in ferromagnetic glass-coated microwire metacomposites. In order to fully exploit the intrinsic structure of the composite, here, we implement the concept of composites plainification by an in-built vertical interface on randomly dispersed short-cut microwires allowing the adjustment of electromagnetic properties to a larger extent. Such interface was modified through arranging wires with different internal structures in two separated regions and by alternating these regions through wire concentration variations associated with polarization differences across the interface. When the wire concentration was equal in both regions, two well-defined transmission windows with varied amplitude and bandwidth were generated. Wire concentration fluctuations resulted in strong scattering changes ranging from broad passbands to pronounced stopbands, demonstrating the intimate relationship between wire content and space charge variations at the interface. This provides a new method to rationally exploit interfacial effects and microstructural features of microwire metacomposites. Moreover, the advantages of enabling tunable scattering spectra by merely 0.053 vol.% of fillers and simple structure make the proposed plainification strategy instrumental to designing filters with broadband frequency selectivity.
The influence of the concentration of alloying components on thermal stability, magnetic and electrical properties of amorphous alloys of Co73-66Fe4,6-3Cr0-9(B,Si)22-29 system was studied by methods of differential scanning calorimetry, XRD, resistometry and magnetometry. The crystallization of several alloys with advanced magnetic characteristics was studied. At continuous heating of the ribbons, either primary or eutectic crystallization was observed depending on the chemical composition of these alloys. Certain tendencies in the anomalous behavior of temperature dependence of electrical resistance of ribbons were revealed. By increasing chromium and metalloids concentrations, we obtained the alloys with relatively low saturation induction and large difference between the Curie temperature and the temperature of crystallization onset. The heat treatment regimes to obtain the best magnetic properties of these alloys were found. Prospective applications of Co73-66Fe4,6-3Cr0-9(B,Si)22-29 amorphous ribbons for fabrication of high sensitive sensors of magnetic field were discussed.
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.
Approaches to modulate magnetoimpedance (MI) in amorphous wires mostly include annealing, ion irradiation, glass coating and patterning, which are mainly based on induction of transverse magnetic anisotropy. Here, through modulating the magnetization distribution across the wire and outer magnetic shell/ inner core ratio, enhanced magneto- and stress-impedance sensitivity were obtained. Such modulation was achieved by coating a Co-based melt-extracted wire with carbon nanotubes (CNT) and graphene oxide (GO) which induced different level of stresses allowing the increase in outer domain shell volume with helicoidal/circular-type magnetic anisotropy in expense of the axially magnetized inner core. Moreover, through controlling nanocarbon thickness, we demonstrated the validity of high frequency impedance measurements to map the magnetic microstructure across the wire and reveal the core–shell interaction and its contribution to MI. The improvement in transversal anisotropy was evidenced by a drastic increase in MI effect from 170% at 10 MHz for uncoated wire to 400% and 300% for CNT and GO-coated wires, respectively. Finally, by developing a planar model with a four-layer structure, the main features of MI curves were reproduced in the simulated curves. Our results establish a simple platform for the design of microwave materials towards a wide range of sensing applications.
Microwire composites possess a wide range of functionalities that can be actively manipulated by magnetic field/stress stimuli or hybridization. Beyond those strategies, here we focus on programming microwave response by designing the wire functional units and assembling them in a specific arrangement. The programming was based on a code type defined by structural relaxation and electromagnetic damping and on a code pattern by wave attenuation, effective conductivity and near-field interaction effects. Structural relaxation was achieved by current annealing the wires, which was reflected in changes in Curie temperature, structural, magnetic and electrical properties. The wave propagation mapped by the transmission coefficient was manipulated by the wire concentration and periodicity and by arrangement of as-cast and annealed wires in the array. Increasing the wire concentration blueshifted the transmission band due to larger conductivity, while decreasing the wire periodicity redshifted the band owing to stronger inter-wire coupling. A larger blueshift was obtained by alternating as-cast and annealed wires due to an overlapped flow closure of fields from the same type of wire in the array. Our strategy demonstrates that macroscopic properties of wire composites can be effectively programmed from materials/structure perspective, which further promotes this concept towards deeper understanding of physical properties and broader applications in fields such as information, energy, and security technologies.
Amorphous ferromagnetic microwires have drawn attention primarily due to their excellent soft magnetic properties as the elements of sensors. In this work, semi-hard magnetic microwires of composition
Fe4.3Co67.7Si11B14Cr3 were obtained after a process of directional crystallization from amorphous state. The XRD analysis of crushed and whole wires identified the formation of the face-centered Co-modification as the main phase of directionally crystallized core alloy, which explains a large increase in anisotropy and coercivity. The application of a magnetic field during crystallization may orient the easy anisotropy axis of crystallites along the wire. This is confirmed by the investigation of crystallite orientation with respect to the wire axis and X-rays direction in diffractometer. The obtained results revealed that the formation of crystallites in amorphous Co-rich microwires occurs with the predominant orientation of the crystallographic direction [111] along the wire axis and the direction of a magnetic field during the directional crystallization process.
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.
There is a pressing need for improving of the high-frequency magneto-impedance effect of cost-effective soft magnetic materials for use in high-performance sensing devices. The impact of the stress-annealing on magnetic properties and high frequency impedance of Fe-rich glass-coated microwires was studied. Hysteresis loops of Fe-rich microwires have been considerably affected by stress- annealing. In stress-annealed Fe- rich microwire we obtained drastic decreasing of coercivity and change of character of hysteresis loop from rectangular to linear. By controlling stress-annealing conditions (temperature and time) we achieved drastic increasing (by order of magnitude) of giant magnetoimpedance ratio. Coercivity, remanent magnetization, diagonal and of-diagonal magnetoimpedance effect of Fe-rich microwires can be tuned by stress-annealing conditions: annealing temperature and time. Observed experimental results are discussed considering relaxation of internal stresses, compressive "back-stresses" arising after stress annealing and topological short range ordering.
The effect of temperature on static and dynamic magnetization in Co-based amorphous microwires was investigated with the aim of potential applications in miniature temperature sensors. The wires of two compositions with different magnetostriction and Curie temperature in glass-cover and after removing the glass layer demonstrated very different temperature behaviour of the magnetization loops and magnetoimpedance. The mechanisms of the temperature effects are related to the residual stress distribution due to fast solidification, the difference in thermal expansion coefficient of metal and glass and the proximity to the Curie temperature. The interplay of these factors may result in a very strong temperature dependence of magnetoimpedance in a moderate temperature range (room temperature −373K). Such elements may be incorporated in various composite materials for a local temperature monitoring.
Testing internal stress/strain condition of polymer composite materials is of high importance in structural health monitoring. We are presenting here a new method of monitoring internal stresses. The method can be referred to as embedded sensing technique, where the sensing element is a glass-coated ferromagnetic microwire with a specific magnetic anisotropy and stress-dependent magnetostriction. When the microwire is remagnetized the sharp voltage is induced which is characterized by high frequency harmonics. The amplitude of these harmonics sensitively depends on various stresses. The microwire of composition Co71Fe5B11Si10Cr3 with the metallic core diameter of 22.8 μm show abrupt transformation of the magnetization process under applied tensile stress owing to the stress-dependent magnetostriction.
We have studied effect of current annealing on domain wall dynamics of FeCoMoB microwires. It was showed that 10 minutes of current annealing corresponds to 1 hour of classical annealing in furnace. Moreover, electrical current flowing through microwire produces Oersted magnetic field and therefore circular magnetic anisotropy is induced during annealing. As a result, induced circular magnetic anisotropy prefers vortex domain wall with velocities up to 3 km/s that can be observed in the current annealed nanocrystalline FeCoMoB microwires with much higher temperature stability.
We have developed sensitive micro magnetic sensors referred to as MI sensors based on magneto-impedance effect in amorphous wires and CMOS IC electronic circuits providing a sharp-pulse excitation. Micro sized MI-HIC chips have been in mass production of electronic compasses by Aichi Steel Corp. since 2002 for mobile phones and since 2010 for smart phones. Recently we have realized pico-Tesla (10-8 Oe) resolution for micro MI sensors making use of ultralow intrinsic magnetic noise in amorphous wires with the pulse magnetoimpedance effect. The pico-Tesla MI sensor is useful especially for bio-magnetic measurements without any magnetic shielding at room temperature. In order to avoid a risk of traffic accident due to noise reduction electric vehicles, an alert system for the pedestrians having a smart phone would be useful, if pico-Tesla MI sensor were built in the smart phones.
In this work, we present a study on the magnetic properties of Joule-heated CoFeSiB glass-covered amorphous microwires under applied stress. A comparison between the magnetic properties of four samples is made: (i) as cast, Joule-heated under (ii) dc current or ac current of (iii) 100 Hz or (iv) 500 Hz. The stress modifies the anisotropy and the domain structure in such a way that it can be studied through magnetoimpedance measurements and ferromagnetic resonance (FMR) dispersion relations (DR) extracted from them. From the fitting of the FMR DR, the magnitude and the orientation of the transverse anisotropy field, as well as an insight into the micromagnetic structure of the microwires were obtained. It was concluded that longitudinal anisotropy dominates the microwire behaviour under zero stress. By applying an increasing stress to the microwires, the inner core with longitudinal anisotropy is surrounded by two concentric outer shells with almost circumferential anisotropies. These magnetic configurations can be explained in terms of the residual stress arising from the wire's manufacturing procedure and the additional applied stress.
A remarkably strong dependence of magnetoimpedance (MI) on tensile stress has been observed in the microwave frequency range for thin CoFeCrSiB glass-coated microwires with an axial anisotropy induced by tension annealing. The relative change in impedance runs into more than 100% at 0.5-1.5 GHz for a characteristic stress of 600 MPa. It was demonstrated that this stress MI is due to the transformation of the anisotropy from the axial toward the circumferential under the effect of applied tension and does not require the assistance of the dc bias magnetic field. Such microwires incorporated into a dielectric matrix may constitute a new sensing medium that is characterized by the stress-dependent effective permittivity. The proposed medium can be used for the microwave visualization of the stress distribution inside of a composite structure or on its surface.
The dependence of the magnetic parameters as switching field H*, coercive field H c and reduced remanence m r , on applied tensile stress σ a has been studied in current annealed amorphous wires. The switching field increases as σ 1/2 a in fully relaxed samples, while in both ‘‘as‐quenched’’ and partially relaxed samples the σ 1/2 a law holds only at high values of σ a . The coercive field increases with σ a in a way similar to H* and m r increases up to the saturation value. This behavior can be explained by taking into account the different magnetic regions that have been proposed for these wires.
The effect of conventional (CA) and stress annealing (SA) on magnetic properties of Fe 74 B 13 Si 11 C 2 glass-coated microwires has been studied. CA treatment does not significantly change the character of the hysteresis loop. Under certain annealing conditions (annealing temperature, T ann ≫300 ° C , applied stress, σ≫700 MPa ) rectangular hysteresis loop transforms into the inclined with magnetic anisotropy field above 1000 A/m. Such phenomenology has been related to the induction of transverse magnetic anisotropy by SA treatment. Under tensile stress the SA annealed microwire recovers rectangular hysteresis loop. Samples subjected to stress annealing show noticeable magnetoimpedance and stress impedance effects in spite of their large magnetostriction. © 2003 American Institute of Physics.
The main bottlenecks limiting the practical applications of current magnetoresistive random access memory (MRAM) technology are its low storage density and high writing energy consumption. Although a number of proposals have been reported for voltage-controlled memory device in recent years, none of them simultaneously satisfy the important device attributes: high storage capacity, low power consumption and room temperature operation. Here we present, using phase-field simulations, a simple and new pathway towards high-performance MRAMs that display significant improvements over existing MRAM technologies or proposed concepts. The proposed nanoscale MRAM device simultaneously exhibits ultrahigh storage capacity of up to 88 Gb inch(-2), ultralow power dissipation as low as 0.16 fJ per bit and room temperature high-speed operation below 10 ns.
This paper discusses two different mechanisms of temperature effects on magnetoimpedance (MI), namely, the internal stress relaxation upon heating and critical behavior of magnetic parameters near the Curie temperature Tc. When a microwire is heated, the residual stress is partially released changing the effective anisotropy, which inevitably leads to the temperature dependence of hysteresis and MI. A very large change in impedance up to 200% with moderate temperature increase (50-70 °C) occurs in microwires of Co66.94Fe3.83Ni1.44 B11.51Si14.59Mo1.69 compositions with high Tc≈340°C where the magnetostriction changes a sign from negative to positive due to stress relaxation. Proper annealing is demonstrated to stabilize such temperature variations in MI. Near the Curie temperature, the impedance undergoes large variations due to a corresponding drop in the magnetization saturation and magnetic anisotropy. The theoretical modelling reveals an increase in the dc initial permeability when approaching Tc, which results in different temperature behaviours of MI at low and high frequencies. This was confirmed experimentally for Co23.67Fe7.14Ni43.08B13.85Si12.26 amorphous microwires (Tc = 62 °C): at a frequency of 10 MHz the impedance increases with temperature until very close proximity of Tc, whilst at a frequency of 300 MHz it continuously decreases with increasing temperature. Controlling the value of Tc the impedance temperature dependence can be realized in the industrial temperature range of 20-100 °C. This has potential applications for developing embedded miniature temperature sensors.
Various thermal treatments have long been known to be effective in tailoring structural and magnetic properties of amorphous ferromagnetic wires, consequently, a desired magnetic anisotropy can be controlled for specific sensing applications. This work deals with the effects of annealing and applied stresses on the magnetization processes and magnetoimpedance (MI) in Co71Fe5B11Si10Cr3 glass-coated microwires having amorphous or partially crystalline structure. The alloy under study has a small positive magnetostriction (approximately 10-8) in its amorphous unstressed state. By applying a tensile stress to amorphous microwires, an abrupt transformation of the hysteresis loop is observed owing to the anisotropy type change due to stress-dependent magnetostriction which changes sign. The modification in the anisotropy type greatly enhances the stress sensitivity of higher frequency harmonics induced during re-magnetization and MI. The wires with a partially crystalline structure did not exhibit a noticeable stress dependence of magnetic properties, but after annealing a significant increase in coercivity was observed after applying a tensile stress. The obtained results were investigated in terms of a magnetostrictive model of magnetic anisotropy offering a reasonable explanation.
The whole set of geometrical, mechanical and magnetic parameters of Co-rich amorphous
ferromagnetic microwires very promising for the development of sensitive stress and Giant Magneto-
Impedance sensors have been determined by means of scanning electron microscopy, selective
nanoindentation and small angle magnetization rotation method. The magnetostriction constants
obtained are sensitive to the true microwire compositions. The experimentally estimated amplitudes of
the residual quenching stress are mainly determined by the ratio of the inner and outer wire diameters.
They are found to be in good correspondence with the theoretical values calculated based on the theory
of viscoelasticity.
We present a concept and prototype of a memory element based on current driven magneto-impedance (MI) effect that stores the binary data (0, 1) as the orientation of the magnetization. The magnetization orientation in the surface layer with tilted anisotropy easy axis can be switched controllably between two stable states by applying current pulses of the appropriate sign, and can be detected by sensing the impedance. We demonstrated the functioning of a non-volatile magnetic memory with a read speed performance up to and above 2 GHz. A prototype of a memory element was realized on a short piece of amorphous microwire, as this material exhibits the highest MI effect, and the required anisotropy can be quite easily obtained. Nevertheless, this concept can be extended to other materials and geometries exhibiting MI effect and possessing a required magnetic anisotropy.
High-frequency properties of magnetic microwires in glass coating and related applications are discussed. In ferromagnetic wires with a spiral type of magnetic anisotropy, the permeability spectra are very wide, and the permeability values may substantially differ from unity in the GHz frequency band. This makes the wires attractive to those trying to design artificial magnetic dielectrics with enhanced and tunable permeability. The applications include controllable absorbing or shielding materials and microwave left-handed materials. This type of anisotropy also results in a large and sensitive magnetoimpedance (MI) effect. Composites with MI wires could be used to engineer a dielectric response that depends on external stimuli including magnetic, mechanical, and thermal forces. This has potential for applications in structural health monitoring.
The effect of both thermal treatments as well as chemical etching treatments on the magnetic behavior has been investigated in nearly-zero magnetostriction glass-coated amorphous (Co1−xMnx)75Si10B15(x=0.08, 0.09, and 0.10) microwires. Such a small change in x results in rather strong changes in the hysteresis loop parameters including coercitivity, Hc, and initial magnetic permeability, μ15. This effect was ascribed to the change of sign of the magnetostriction constant with a proper combination of the coercivity and relatively high initial permeability for the as-cast x=0.09 sample. Thermal treatment (temperatures 100–200 °C for 0.5–2 h) as well as chemical etching in 20% diluted fluoridric acid with duration from 0.5 up to 50 min modify this magnetic parameters owing to the internal stresses relaxation process. In particular, annealing under applied magnetic field (field annealing) can improve more significantly these magnetic parameters: increasing both Hc and μ15. Such phenomenology can be interpreted considering the noticeable longitudinal magnetic anisotropy induced by the combined effects of the magnetic field and strong internal stresses arising from the coating during the thermal treatment. The reduction of the glass coating thickness by chemical etching leads to a decrease of the internal stresses from a coating and, consequently, to a decrease of the transverse magnetoelastic anisotropy. Such decrease of anisotropy plays a role similar to that induced by field annealing on the hysteretic behavior.
The giant magnetoimpedance (GMI) effect consists of the huge change of both real and imaginary parts of the impedance upon the application of static magnetic field. The relative change of impedance can reach ratios up to around 700%, with extremely large sensitivities in the very low field region. The magnetoimpedance phenomenon is observed in soft magnetic metals. Apart from the applied DC field, the main parameter determining GMI is the frequency of the driving current (which generates the circular AC driving magnetic field). In addition to fundamental aspects related to micromagnetics and to magnetization dynamics, the main interest of GMI effect lies in the large number of possibilities that it offers to technical researchers for employing this phenomenon as sensing principle in novel sensor devices. Under particular suitable conditions (ultrasoft magnetic character, adequate magnetic anisotropy, and adequate geometry), the GMI material undergoes modifications in its impedance in the presence of external agents such as static magnetic field and mechanical stress. Consequently, this variation of impedance is used as the measurement principle to sense the correlated changes in magnetic field strength, stress, or torsion. The chapter describes various types of sensors based on GMI, such as magnetic field sensors (wire and thin film technologies); current, position and rotation sensors (applications that derive from field sensing); stress sensors; and microwave applications, along with the particular characteristics necessary for the materials to be employed in GMI applications.
The magnetic aftereffect (MAE) δr/r, the perminvar critical field Hcr, the initial susceptibility x10, the coercive field Hc, and the magnetically induced anisotropy (MIA) Kuin in (Co1−xFex)75Si15B10 (0 ≦ x ≦ 1) metallic glasses are examined. The ribbons are subjected to different kinds of heat treatments: annealings in parallel and transverse magnetic field. The results are discussed in terms of the theory of two-level systems.Die magnetische Nachwirkung δr/r, das kritische Feld Her des Perminvar-Effekts, die Anfangs-suszeptibilität x10, die Koerzitivfeldstärke Hc und die feldinduzierte Anisotropie Kuin in ferromagneti-schen Legierungen werden untersucht. Die amorphen Legierungen werden unterschiedlichen Warme-behandlungen unterworfen: Magnetfeldtempern im parallelen und senkrechten Feld. Die Resultate werden mit der Theorie der Zwei-Niveau-Systeme beschrieben.
In this work, we present a domain wall dynamics study on Joule heated Co68.15Fe4.35Si12.5B15 glass-covered amorphous microwires. Three samples were annealed with: (i) DC current or AC current with frequency of (ii) 100Hz and (iii) 500Hz. The current density was equivalent to an annealing temperature of 250°C. The permeability spectra were obtained from the magnetoimpedance measurements at different axial applied stresses. Contributions from domain wall motion and magnetization rotation to the total permeability were separated and analyzed. Without axial stress, the samples present a longitudinal anisotropy, which is converted to a core–shell domain structure (bamboo-like structure) when stress is applied. A huge increase of domain wall component of the permeability until a critical stress followed by a linear reduction is present in all samples. The main difference is that the domain wall contribution to the permeability and the critical stress are lowest for the DC annealed sample and reach a maximum for the sample annealed at 500Hz. The results are discussed in terms of the field-induced anisotropy during the annealing and the internal stress distribution.
Technological aspects of the Taylor–Ulitovsky method for fabricating glass-coated microwires with different structures of metallic nucleus are discussed. The main parameters of the process can be distinguished as follows: a casting rate of microwire and its limits, cooling rate of the metal core, geometrical characteristics and alloy composition. The casting rate is important in determining the upper and lower limits of the diameter of microwire. Depending on the critical quenching rate (104–107K/s), metastable, amorphous or supersaturated state phases are obtained. Mixed structures consisting of micro- and nanocrystallites embedded into the amorphous matrix can also be formed. During the fabrication process, strong internal stresses are generated, which determine some of the most interesting properties of these materials. In particular, magnetic properties depend mostly on the magnetoelastic anisotropy arising from the coupling of the internal stresses with magnetostriction constant.
Induced magnetic anisotropy and changes of the saturation magnetostriction are reported for a Co-rich (Co-Fe) amorphous wire after annealing under tensile stress. On the other hand, it is confirmed that in wires, magnetostriction depends linearly on applied stress. Experimental results of these parameters show a similar behavior to that reported in metallic glass ribbons with similar composition.
Two approaches for obtaining asymmetrical magnetoimpedance (MI) characteristics in Co-based negative magnetostrictive amorphous wires are analyzed in terms of the surface impedance tensor , which is expressed in the form of orthogonal expansions in Bessel functions in a general case of a helical magnetization. The asymmetry in MI behavior with respect to an axial dc magnetic field can be related to either a certain asymmetric arrangement of the dc magnetic configuration or a contribution to the wire voltage due to the ac cross-magnetization process (represented by the off-diagonal component of ). The first case is realized in a wire having a helical anisotropy and subjected to an ac current superposed with a dc current. In the other approach, the asymmetric voltage response can be obtained by applying the ac current in series through the wire and the coil mounted on it. No helical anisotropy is required in this case. These kinds of asymmetrical MI are especially important for developing autobiased linear MI sensors. © 1999 American Institute of Physics.
The calculation of the residual stress tensor components in glass-coated amorphous ferromagnetic microwire is carried out on the basis of the theory of viscoelasticity. The approach takes into account the relaxation of the stresses both in a metallic core and a glass shell of the wire within a certain temperature interval near the point of the wire's vitrification. The distribution of the residual stresses is investigated as function of mechanical characteristics of metallic core and glass shell at different ratios of the metallic core radius to the total wire radius. The magnetic behaviour of a glass-coated amorphous microwire with small negative magnetostriction is analysed and is shown to be consistent with the experimental data.
a b s t r a c t Structural, magnetic and mechanical properties of Co-based magnetic microwires and their composites had been investigated. It was found that annealing amorphous microwires at 600 °C caused a drastic var-iation in the amorphous structure due to crystallization and consequently degraded the soft magnetic properties of the microwires. The tensile tests on the single microwires of different size with and without glass-coated layer revealed a coherent correlation between the mechanical properties and the wire geometry. When compared with single magnetic microwires, the magnetic and magneto-impedance properties of composites were much improved. The strong field dependence of the effective permittivity and transmission/reflection parameters in the Gigahertz range of the composites containing short wires or arrays of continuous wires indicated that these new composites are promising candidate materials for a variety of self-sensing applications.
Recognizing the importance of magnetic thin wires for science and technology, the 6th International Workshop on Magnetic Wires was held on 6–7 July 2010, in Bodrum, Turkey. A wide range of topics were addressed from technological problems of micro- and nanowire fabrication, to advanced physical effects and novel applications. Furthermore, critical discussions on the present state of knowledge and future trends arose during the Panel Session on microwires. In the present report, the main aspects addressed at the Discussion Panel and at workshop presentations are summarized with the aim to state the present and future perspectives on these wire systems. This report is focused upon four topics chosen for broad discussions at the Panel: Fabrication and processing, Magnetization reversal and Dynamics, High-frequency properties, and Technological applications.
A simple and fully gate-voltage-controlled magnetic random access memory is designed based on anisotropic magnetoresistance. This multiferroic memory device consists of just a single magnetic film grown on a ferroelectric layer with bistable in-plane anisotropic ferroelastic or piezo strains induced by out-of-plane voltages. It can simultaneously achieve ultrahigh storage density, ultralow energy consumption, and GHz high-speed operation at room temperature.
An asymmetrical and sensitive magneto-impedance effect was
realized in twisted FeCoSiB and CoSiB amorphous wires magnetized with a
dc-biased ac current, in impedance up to about 120%/Oe. The asymmetrical
magneto-impedance (AMI) is useful to construct linear field sensors
without any dc bias field. Mechanisms of the AMI are also
discussed
A bistable microwire reader is an inductive type sensor that measures the fast magnetic flux reversals in ferromagnetic microwires having predominant longitudinal magnetisation. The signal processing in such readers is a challenging problem due to short induced pulses, pile up effect, pickup noise, and ringing distortion in the pickup coils. In our present work, analog and digital reading schemes for multi-bit tags made of several bistable microwires have been proposed. The performance of an analog reader can be sufficient for well separated pulses. However, the digital algorithms deliver a clearer output signal with better pulse resolution in the case of the pulse pile up effect. In turn, this enables reliable code recognition. Here, two digital algorithms have been tested. The digital low-pass Gauss filter effectively suppresses the pickup noise and ringing oscillations. The deconvolution algorithm constitutes the inverse task with respect to the convolution operator defining the pickup voltage output. This algorithm recovers the initial pulse profiles and provides the highest possible resolution of a pulse series. The obtained results will be useful for the creation of a robust reader for bistable microwire tags that can be implemented in recycling projects, marking of items, and fraud protection.
Method of continuous casting of glass coated microwire
- A V Ulitovsky
- I M Maianski
- A I Avramenco
Ulitovsky A. V., Maianski I. M. & Avramenco A. I., Method of continuous casting of glass
coated microwire, USSR Patent, No.128427, 1960, Bulletin No. 10, p. 14.
Mechanical properties and internal quenching stresses in Co-rich amorphous ferromagnetic microwires
- V Kostitsyna
- S A Gudoshnikov
- A V Popova
- M I Petrzhik
- V P Tarasov
- N A Usov
- A S Ignatov
V. Kostitsyna, S.A. Gudoshnikov, A.V. Popova, M.I. Petrzhik, V.P. Tarasov, N.A. Usov, A.S.
Ignatov, Mechanical properties and internal quenching stresses in Co-rich amorphous
ferromagnetic microwires. J. Alloys Compd. 707 (2017) 199-204
Fe 5 B 11 Si 10 Cr 3 Amorphous Microwires
Fe 5 B 11 Si 10 Cr 3 Amorphous Microwires, IEEE Trans. on Magn., V. 53, (2017) 2003106.