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In this article we evaluate the possibility of using glass coated magnetic microwires as an alternative to optical fiber devices in structural health monitoring in the railway industry. The effect of applied stress on hysteresis loops of Fe71.80B13.27Si11.02Nb2.99Ni0.92 and Co65.34Si12.00B10.20Cr8.48Fe3.90Mo0.08 microwires has been studied and analyzed. An interpolation function has been obtained relating the coercitivity Hc with the applied stress. [ABSTRACT FROM AUTHOR]

In this article, we studied the effect of annealing (600 °C for 1 h) and the applied magnetic field from 50 Oe to 20 kOe of Co2FeSi glass-coated microwires with ordered L21 structure prepared by Taylor–Ulitovsky technique on the magnetic behavior. The as-prepared and annealed samples show a ferromagnetic behavior at the range of measuring temperature (5 to 400 K) and magnetic field (50 Oe to 20 kOe). M–H loops of as prepared sample do not show a squared shape. Meanwhile, perfectly squared hysteresis loops have detected for the annealed sample. In addition, annealed sample shows high magnetization M/M5K ratio, coercivity, and anisotropy field, as-compared to the as-prepared one. The annealed sample shows considerable irreversibility when the magnetic behavior changes with temperature upon the applied magnetic field at 50 and 200 Oe. Such irreversibility does not found in the as-prepared sample measured at the same magnetic field due to mixed amorphous and crystalline structure. By increasing the external magnetic field higher than 200 Oe and up to 20 kOe a gradual changing in the magnetic behavior has been detected where the irreversibility disappeared at applying magnetic field about 1 kOe and the magnetic behavior is totally change by increasing the external magnetic field up to the maximum 20 kOe. The difference in the magnetic behavior of the annealed glass-coated Co2FeSi glass-coated microwires indicates the effect of internal stresses induced by the presence of the glass-coating and the annealing-induced recrystallization. [ABSTRACT FROM AUTHOR]

Giant magnetoimpedance, GMI, effect and magnetic properties upon temperature influence of as-prepared and stress-annealed amorphous Fe75B9Si12C4 glass-coated microwires produced by the Taylor-Ulitovsky technique are analyzed. Remarkable change in the hysteresis loops and GMI effect is observed for both samples upon heating. Tuning of the stress-annealing conditions allows one to vary the temperature dependence. Furthermore, it is observed almost complete reversibility of the changes induced by the temperature. Observed dependences are explained by the heating effect on the internal stresses relaxation, by the modification of the thermal expansion coefficients of the metallic nucleus and the glass coating, and by the Hopkinson effect. [ABSTRACT FROM AUTHOR]

A gradual change in the hysteresis loop of Co-rich glass-coated microwire sample stress-annealed at variable temperature is observed. Such microwire annealed with a temperature gradient presents also variable squareness ratio along the microwire length, L. Obtained graded anisotropy has been attributed to a gradual modification of the domain structure along the microwire. Accordingly, we propose a rather simple route to design graded magnetic anisotropy in a magnetic microwire. [ABSTRACT FROM AUTHOR]

Influence of Joule heating on magnetic properties and GMI effect of Fe75B9Si12C4 glass-coated microwires was studied. A decrease in coercivity after Joule heating is observed, while hysteresis loops of Joule heated samples maintain a rectangular shape. However, a remarkable increase in GMI ratio is observed in Joule heated samples. Observed GMI ratio improvement has been discussed considering magnetic anisotropy induced by Oersted magnetic field during Joule heating and internal stress relaxation. A remarkable GMI effect improvement observed in Joule heated Fe-rich microwires, along the fact that Fe is a more common, less expensive metal than Co, makes them suitable for magnetic sensor applications. [ABSTRACT FROM AUTHOR]

The giant magnetoimpedance (GMI) effect, as well as the magnetic and magneto-optical properties, of Co69.2Fe4.1B11.8Si13.8C1.1 and Fe73.8Cu1Nb3.1B9.1Si13 amorphous microwires is studied. It is observed that the magnetic properties and the GMI effect of the Co-rich microwire can be tuned by heat treatment. A high GMI effect has been observed in as-prepared Co-rich microwires. After appropriate annealing of the Co-rich microwires, fast domain wall propagation and a GMI effect can be simultaneously observed in the same sample, and annealing is seen to affect both the diagonal and off-diagonal GMI components. Using complementary studies of the bulk and surface magnetic properties, an attempt is made to explain the great difference observed in the GMI properties of Co- and Fe-based microwires exhibiting very similar bulk hysteresis loops. [ABSTRACT FROM AUTHOR]

We present experimental studies related to the influence of annealing on domain wall (DW) dynamics and magnetic hysteresis of Fe-Ni-rich microwires. As-prepared and annealed Fe62Ni15.5Si7.5B15 and Fe49.6Ni27.9Si7.5B15 microwires present perfectly rectangular hysteresis loops and single DW propagation. DW velocity, v, DW mobility, S, and coercivity, Hc, of both studied microwires have been considerably affected after annealing. In Fe62Ni15.5Si7.5B15 microwires, we observed a gradual S increase with annealing time, tann, increasing. However, a non-monotonic S (tann) dependence was observed in Fe49.6Ni27.9Si7.5B15 microwires. We discussed observed dependencies in terms of different magnetoelastic anisotropy, domain walls stabilization, and different Curie temperatures of studied microwires. [ABSTRACT FROM AUTHOR]

We report on tailoring the hysteresis loops of arrays containing Fe- and Co-rich microwires utilizing effects of magnetostatic coupling. The interacting wires of both types may produce a complex magnetic response and highly specific spectral characteristics. For Fe-rich microwires we observed step-wise hysteresis loops with a number of Barkhausen jumps equal to a number of Fe-rich microwires. For arrays of Co-based microwires the change in the hysteresis loop shape is less pronounced and is characterized by an increase in the magnetic anisotropy due to interwire interactions. The most interesting multistage magnetization behavior is obtained for arrays containing both types of wires and is characterized by field intervals with both gradual and abrupt magnetization changes. We also investigated the spectral properties associated with each type of magnetization process. The field plots for higher harmonics are highly specific and can be used to discriminate the types of wires in the array. [ABSTRACT FROM AUTHOR]

We report on preparation and magnetic properties of Fe71.7B13.4Si11Nb3Ni0.9 glass-coated microwire with metallic nucleus diameter d = 103 μm and total diameter D = 158 μm prepared by Taylor-Ulitovsky method. Amorphous structure of as-prepared microwires is confirmed by X-ray diffraction. As-prepared glass-coated microwires present relatively high GMI effect (about 50%) and relatively low coercivity (about 25 A/m). Additionally, as-prepared sample present rectangular hysteresis loop and fast single domain wall propagation with domain wall mobility of about 11,9 m2/As. After annealing we observed considerable improvement of the GMI ratio (from 50% up to 100%). Observed GMI effect improvement has been attributed to the stresses relaxation. From aforementioned studies we can conclude that the Taylor-Ulitovsky technique allows us to obtain thick ferromagnetic microwires with good magnetic properties and GMI effect suitable for industrial applications. [ABSTRACT FROM AUTHOR]

The influence of stress-annealing on the magnetic softness and the magnetoimpedance effect of Fe-and Co-based glass-coated microwires is studied. As-prepared Co-rich glass-coated microwires present better magnetic softness and rather higher magnetoimpedance ratio with a double-peak dependence, typical for materials with transverse magnetic anisotropy. As-prepared Fe-based microwires present a rectangular hysteresis loop with a coercivity an order of magnitude higher and a magnetoimpedance ratio of an order of magnitude lower. Stress-annealing of Co- and Fe-based glass-coated microwire allows considerable magnetoimpedance ratio increasing. The impact of stress-annealing is especially pronounced in a Fe-based microwire, where transverse magnetic anisotropy, large (an order of magnitude) improvement of the magnetic softness and magnetoimpedance ratio are observed. In Co-based microwire a magnetoimpedance ratio improvement for short annealing time and a change of hysteresis loop from linear to rectangular are observed. Observed stress-induced anisotropy and related changes of magnetic properties are discussed considering internal stresses relaxation and “back-stresses”. Obtained experimental results yield new and important insights into the influence of stress-induced magnetic anisotropy on the magnetoimpedance effect and hysteresis loops of glass-coated microwires. [ABSTRACT FROM AUTHOR]

We present an overview of the factors affecting soft magnetic properties and giant magnetoimpedance (GMI) effect as well as of post processing tools allowing optimization of magnetic softness and GMI effect of thin amorphous wires. Generally low coercivity and high GMI effect have been observed in as-prepared Co-rich microwires. The magnetoelastic anisotropy is one of the most important parameters that determine the magnetic softness and GMI effect of glass-coated microwires. Annealing at adequate conditions can be very effective for manipulation the magnetic properties of amorphous ferromagnetic glass-coated microwires. After annealing of Co-rich we can observe transformation of inclined hysteresis loops to rectangular and coexistence of fast magnetization switching and GMI effect in the same sample. Using stress-annealing, GMI effect of Co-rich microwires can be increased. We demonstrated that the switching field value of microwires can be tailored by annealing in the range from 4 to 200 A/m. Similarly stress-annealing allows induction of transverse magnetic anisotropy and improvement of magnetic softness and GMI effect in amorphous Fe-rich microwires. On the other hand in Fe-rich FeCuNbSiB microwires after appropriate annealing we observed considerable magnetic softening and GMI effect enhancement. [ABSTRACT FROM AUTHOR]

We report on comparison of magnetic properties and GMI effect of as-prepared, annealed and stress-annealed Fe- and Co-rich microwires. Generally after annealing hysteresis loop of Co-rich microwires becomes rectangular. Stress annealed Co-rich microwires exhibit lower coercivity as-compared with conventionally annealed samples. Additionally we observed increasing of GMI ratio after stress annealing and its decreasing after conventional annealing. In the case of Fe-rich microwires the hysteresis loops of stress annealed samples present linear shape with low coercivity. Considerable improvement of GMI effect in Fe-rich microwires after stress annealing is observed. For interpretation of observed changes of hysteresis loops after stress annealing we considered internal stresses relaxation and different mechanisms of stress-induced anisotropy. Observed versatile properties of stress annealed glass-coated microwires with enhanced and tunable soft magnetic properties make them suitable for technological sensing applications. [ABSTRACT FROM AUTHOR]

We have studied the effect of annealing conditions on magnetic properties of amorphous CoFeNi-based glass-coated 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. [ABSTRACT FROM AUTHOR]

We studied the influence of two different kind of annealing, conventional annealing and current annealing, on the magnetic and magneto-transport properties of amorphous Co-Fe rich glass-coated microwires with the nominal composition Co69.2Fe4.1B11.8Si13.8C1.1 fabricated by Taylor-Ulitvosky technique. At a certain annealing conditions we have been able to obtain high domain wall velocity with perfectly rectangular hysteresis loop, high giant magneto-impedance response (GMI) and almost linear with low hysteretic off-diagonal GMI response simultaneously in the same sample. Such results could be essential from application's point of view. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

We report on tailoring of magnetic properties of Fe- and Co-rich microwires through magnetostatic coupling among them. We studied hysteresis loops of the arrays containing different number of the CoFeNiBSiM and FeBSiC amorphous microwires. FeBSiC microwires have rectangular hysteresis loop, while CoFeNiB1SiM with vanishing magnetostriction constant posses inclined hysteresis loop with low coercivity. The presence of neighboring microwire (Fe either Co-based) significantly modifies hysteresis loop of whole microwire array. In a microwire array containing Fe-based microwires, we observed splitting of the initially rectangular hysteresis loop with a number of Barkhausen jumps correlated with number of Fe-rich microwires. In Co-Co arrays, we observed a change of inclination of overall hysteresis loop, and consequently magnetic anisotropy field under influence of the additional of Co-based microwire. In the case of mixed arrays containing Fe and Co-rich microwires, we were able to obtain irregular hysteresis loops with unusual shape. In this case, considerable increase of harmonics has been observed. Magnetic field amplitude and frequency affect the behavior of all studied arrays. Increasing the amplitude the shape of hysteresis loop of microwire array containing Fe-based microwires transforms from multi-step to single above certain magnetic field amplitude. In the array with Co-based microwires, we observe a change of coercivity. Observed dependences have been attributed by us to the magnetostatic interaction between the microwires with different magnetic domain structure. Together with the conventional method, such as thermal treatment, designing of arrays containing different types of microwires can serve for tailoring of their magnetic properties. [ABSTRACT FROM AUTHOR]

This work is devoted to the study of the magnetization reversal in the Co-rich glass covered microwire with nearly-zero magnetostriction in the presence of super high frequency (SHF) (about 1 GHz) circular magnetic field that is important for the elucidation of GMI mechanism. Magnetic domain imaging has been performed by means of magneto-optical Kerr effect (MOKE) polarizing microscopy. Local hysteresis loops were obtained from the magneto-optic intensity as a result of images processing. The increase of the SHF field amplitude causes the change of the magnetization reversal mechanism - the rotation of the magnetization dominates. Also the hysteresis loop has an asymmetric shape that confirms the competition between stable and meta-stable helical magnetic states. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

We present an overview of the factors as well as post processing tools allowing optimization of magnetic softness and GMI effect of rapidly quenched materials: microwires and ribbons. Generally, low coercivity and high GMI effect have been observed in as-prepared Co-rich compositions. Annealing at adequate conditions can be very effective for manipulation of the magnetic properties and GMI effect of amorphous and nanocrystalline rapidly quenched materials. After annealing of Co-rich compositions, we can observe transformation of inclined hysteresis loops to rectangular. However, at certain annealing conditions GMI effect can be improved. Using stress-annealing, GMI effect of both Fe-rich and Co-rich microwires as well as of amorphous ribbons can be improved. On the other hand, in Fe-rich FeCuNbSiB microwires after appropriate annealing we observed considerable magnetic softening and GMI effect enhancement. The other promising post-processing allowing GMI effect optimization is Joule heating. Image 1 • Trends in optimization of GMI effect in amorphous and nanocrystalline materials. • Magnetic softening of Fe-rich microwires after stress-annealing or nanocrystallization. • Improvement of GMI effect after Joule heating of Co-rich microwires. • Optimization of GMI effect after post-processing of Co-rich amorphous ribbons. • Improvement of GMI effect after annealing and stress-annealing of Co-rich microwires. [ABSTRACT FROM AUTHOR]

Processing by stress-annealing (450 MPa, 300 °C, 1 h) the glass-coated microwire of Fe 75 B 9 Si 12 C 4 composition a macroscopic magnetic anisotropy with a circular component is developed. This anisotropy very significantly improves the giant magnetoimpedance (GMI) effect with respect to the observed in the as-prepared microwire. The analysis of the GMI response as a function of the frequency (10–1000 MHz) opens new lights to understand the distribution of the magnetic anisotropy inside the glass-coated microwire. We have investigated the GMI response of the stress-annealed Fe 75 B 9 Si 12 C 4 glass-coated microwire. From the frequency dependence of the GMI we have analyzed the distribution of the magnetic anisotropy inside the metallic nucleus obtaining good agreement with the average value of the anisotropy field deduced from the hysteresis loop of the bulk. From measured magnetic field dependences of GMI ratio we evaluated the frequency and magnetic field dependences of the penetration depth. We found that the minimum penetration depth of Fe 75 B 9 Si 12 C 4 microwire decreases from about 1.5 μm down to 0.8 μm after stress annealing. Obtained dependences demonstrate that the minimum penetration depth value as well as the frequency and magnetic field dependences are considerably affected by the stress-annealing. Image 1 • Preparation of thick glass-coated amorphous microwires. • Improvement of GMI effect of microwires by -annealing. • Fast single domain wall propagation with domain wall mobility of about 11,9 m2/As. • Enhancement of domain wall propagation by annealing. • Change of Hysteresis loop of microwires from rectangular to linear after stress annealing. [ABSTRACT FROM AUTHOR]

We studied the effect of applied tensile stresses on magnetic properties of Fe- and Co-rich amorphous glass-coated microwires. Rising of magnetic anisotropy field upon tensile stress in Co-rich glass-coated microwires is described by a linear dependence. Furthermore, decrease of magnetic susceptibility upon tensile stress is observed in Co-rich microwires. A monotonous increase in the coercivity and the switching field upon tensile applied stress is observed for as-prepared Fe-rich microwire. Stress induced magnetic bistability consisting of transformation of hysteresis and onset of rectangular hysteresis loop upon tensile stress, σ , of about 22.5 MPa is observed in stress-annealed Fe-rich microwires. Such stress-induced magnetic bistability results in considerable growing of coercivity and remanent magnetization in stress-annealed Fe-rich microwires. The rising in the coercivity and the switching field upon applied tensile stresses in stress-annealed Fe-rich microwires with stress induced magnetic bistability (at σ > 22.5 MPa) is roughly described by the σ ½ dependence, as previously reported for the wires with spontaneous magnetic bistability. Consequently, stress-annealing of Fe-rich microwire allows beneficial enhancement of the stress dependence of coercivity. Observed dependencies are discussed considering stress dependence of the magnetostriction coefficient in Co-rich glass-coated microwires, internal stresses redistribution and domain structure rearrangement in stress-annealed Fe-rich microwires upon applied tensile stresses. Image 1 • Linear increase in the magnetic anisotropy field upon stress in Co-rich microwires. • Decrease in the magnetic susceptibility upon applied stress in Co-rich microwires. • Observation of stress induced magnetic bistability in stress-annealed Fe-rich microwires. • Enhanced stress dependence of coercivity in stress-annealed Fe-rich microwires. • Observation of σ ½ dependence of switching field in stress-annealed Fe-rich microwires. [ABSTRACT FROM AUTHOR]

We studied effect of annealing on Giant magnetoimpedance (GMI) effect and magnetic properties of amorphous Fe and Co-rich microwires. High GMI effect has been observed in as-prepared Co-rich microwires. We observed that changing the annealing conditions we can obtain a great variety of properties in Co-rich microwire. High domain wall (DW) velocity and rectangular hysteresis loops we observed in heat treated Co-rich microwires. We observed increasing of the DW velocity under stress and coexistence of the GMI effect and fast DW propagation in the Co-rich microwires annealed at certain conditions. Fe-rich microwires with similar bulk hysteresis loop do not present considerable GMI effect. We assume that the outer domain shall of the annealed Co-rich microwire exhibiting both fast DW propagation and GMI effect has high circumferential magnetic permeability. Observed fast DW propagation in both kind of microwires is related to the fast magnetization switching within the single domain axially magnetized inner core, i.e. related to the remagnetization process of the inner part of the microwire. [ABSTRACT FROM AUTHOR]

• Remarkable improvement of GMI effect in Joule heatedCo -rich microwires. • Interpretation of the GMI effect improvement considering circumferential magnetic field associated to Joule heating. • Superior GMI ratio of Joule heated microwire in the frequency range up to 400 MHz. [Display omitted] The effect of Joule-heating on hysteresis loops and giant magnetoimpedance effect, GMI; of Co 69.2 Fe 3.6 Ni 1 B 12.5 Si 11 Mo 1.5 C 1.2 glass-coated microwire is studied. Joule heating performed at suitable conditions prevents the magnetic hardening observed during conventional furnace annealing of the studied microwires. A remarkable GMI ratio improvement is observed as compared to as-prepared annealed and even stress-annealed microwires. Observed magnetic softening and GMI ratio improvement have been discussed considering magnetic anisotropy induced by Oersted magnetic field during Joule heating and internal stresses relaxation. [ABSTRACT FROM AUTHOR]

In this paper we provide results on effect of post-processing on magnetic properties (giant magnetoimpedance, GMI, effect and domain wall dynamics) of Fe 71.7 B 13.4 Si 11 Nb 3 Ni 0.9 glass-coated microwire with metallic nucleus diameter d = 103 μm and total diameter D = 158 μm prepared by Taylor-Ulitovsky method. Amorphous structure of as-prepared wires is confirmed by X-ray diffraction and electronic microscopy. As-prepared glass-coated wires present relatively low GMI ratio (about 50% at 500 MHz) and relatively low coercivity (about 25 A/m). Additionally, as-prepared sample present rectangular hysteresis loop and fast single domain wall propagation with domain wall mobility of about 11,9 m2/As. After annealing (either under tensile stress or without stress) we observed considerable improvement of the GMI ratio (from 50% up to 220% at 200 MHz) and domain wall mobility up to 15,5 m2/As. Observed GMI effect and domain wall mobility improvement has been attributed to the stresses relaxation and creep anisotropy. We demonstrated that the Taylor-Ulitovsky technique is suitable for preparation of "thick" Fe based amorphous microwires with good magnetic properties and GMI effect suitable for industrial applications. Image 1 • Preparation of thick glass-coated amorphous microwires. • Improvement of GMI effect of microwires by -annealing. • Fast single domain wall propagation with domain wall mobility of about 11,9 m2/As. • Enhancement of domain wall propagation by annealing. • Change of Hysteresis loop of microwires from rectangular to linear after stress annealing. • Enhanced GMI ratio of thick microwires in a wide frequency range. [ABSTRACT FROM AUTHOR]

[Display omitted] • Gradual modification of the hysteresis loops along the microwire length of Fe-rich stress-annealed in temperature gradient. • Gradual modification of the hysteresis loops along the microwire length Co-rich annealed in temperature gradient. • Essentially non-uniform domain wall propagation in microwires with graded magnetic anisotropy. • A faster DW propagation is observed in the microwire segments with transverse induced magnetic anisotropy. We observed that the annealing at variable temperature allows to develop amorphous magnetic microwires with graded magnetic anisotropy. In such microwires, annealed with a temperature gradient, gradual variation of the hysteresis loops along the microwire length is observed. The peculiarity of such microwires with graded magnetic anisotropy and rectangular hysteresis loops is that in such microwires the energy landscape and hence the domain wall features, such as the domain wall velocity can be effectively controlled. Obtained spatial distribution of magnetic anisotropy must be attributed to a gradual modification of the domain structure along the length of the microwires annealed in a temperature gradient. Accordingly, we propose a rather simple route involving -annealing in a temperature gradient to design graded magnetic anisotropy in magnetic microwires. [ABSTRACT FROM AUTHOR]

We have studied the magnetic properties and domain wall dynamics in Fe-rich microwires subjected to stress-annealing. The hysteresis loops of Fe-rich microwires were considerably affected by stress-annealing. We obtained drastic decrease in coercivity and change in the character of hysteresis loops from rectangular to linear in stress-annealed Fe-rich microwires. For the wires after stress-annealing at variable temperatures we obtained a graded magnetic behavior with local hysteresis loops shapes and features (coercivity, remanent magnetization) changing along the sample length. In the samples subjected to local stress-annealing we created an artificial source of domain wall injection allowing the manipulation of domain wall dynamics. The observed stress-induced anisotropy could be related to the internal stress relaxation after annealing and the interplay of compressive “back-stresses” arisen after stress annealing and axial internal stresses. [ABSTRACT FROM AUTHOR]

In the current work, we demonstrate that the magnetic and structural properties of Ni 2 FeSi glass-coated microwires are strongly dependent on annealing conditions. A noticeable change in the magnetic and structural properties has also been compared to as- prepared samples. Annealing conditions increase the crystalline phase content from 34% to 72% for annealing duration 1 h and 6 h, respectively. While as- prepared samples show square hysteresis loops for a wide range of measuring temperatures, annealed samples show inclined hysteresis loops shape. Additionally, a marked increase in coercive and magnetic anisotropy fields has been observed for annealed samples as compared to as- prepared ones at and below room temperature. Meanwhile, highly reduced magnetic remanence was measured in the as-prepared samples. Temperature dependence of the coercivity shows anomalous behavior for as-prepared and annealed samples as well. An increase in the magnetization of the metallic nuclei of Ni 2 FeSi glass-coated observed in annealed microwire has been attributed to the internal stresses relaxation caused by annealing. The anomalous magnetic behavior at low temperature is due to the coexistence of ordered and disordered phases induced by annealing conditions. The difference in magnetization behavior, remanence, and coercivity values for Ni 2 FeSi glass-coated microwires samples indicates the influence of internal stresses created by the presence of the glass coating. These findings reveal the sensitivity of Heusler-based glass-coated microwires to temperature and annealing conditions, which will open the door to the design of spintronic devices and sensing applications. • Satisfactory production of Ni 2 FeSi Heusler alloy glass-coated microwires. • Strong dependence of the magnetic properties Ni 2 FeSi Heusler alloy glass-coated microwires on the annealing conditions. • Magnetic softening of Ni 2 FeSi glass-coated microwire upon annealing. • Anomalous magnetic behaviour at low temperature, observed for annealed at 873 K samples. • Ni 2 FeSi glass-coated microwires sensitivity on annealing conditions makes them suitable for sensors and spintronic devices. [ABSTRACT FROM AUTHOR]

We studied the influence of post-processing on magnetic properties of Fe-rich microwires and defined the routes to obtain Fe-rich cost-effective microwires with unique combination of magnetic properties allowing observation of fast and single domain wall, DW, propagation and Giant Magnetoimpedance, GMI, effect in the same microwire. By modifying the annealing conditions, we have identified the appropriate regimes allowing to achieve remarkable improvements in GMI ratio and single DW dynamics. The observed experimental results are discussed considering the radial distribution of the magnetic anisotropy and the correlation of the GMI effect and DW dynamics with hysteresis loops. Image, graphical abstract [ABSTRACT FROM AUTHOR]

The Giant magneto-impedance (GMI) effect in the frequency range 10–1000 MHz and surface magnetic characterization using the magneto-optical Kerr effect (MOKE) in (Co 63 Ni 37) 75 Si 15 B 10 amorphous ribbon were studied. The GMI ratio increases with a frequency up to around 500 MHz followed by a slow decrease. Observed dependence of GMI ratio is discussed by considering the frequency dependencies of the skin depth penetration and magnetic permeability. MOKE in the transverse and longitudinal applied magnetic field to the ribbon direction configurations provides images of magnetic domain structure and hysteresis loops of the two surface sides of the ribbon. An inclined magnetic structure with respect to the longitudinal direction of the ribbon was observed. This inclined magnetic structure is related to a significant transverse component of the magnetic susceptibility tensor, which is a prerequisite to observe GMI effect. The magnetic anisotropy field evaluated from the hysteresis loop with the transverse applied magnetic field configuration is in agreement with the longitudinal magnetic field necessary to obtain the maximum GMI ratio. The MOKE characteristic of two sides ribbon is quite vertical associated to large Barkhausen jumps because the anisotropy axis is, in this configuration, parallel to the applied magnetic field. • The GMI ratio increases with a frequency up to around 500 MHz followed by a slow decrease. • Inclined magnetic structure is related to a significant transverse component of the magnetic susceptibility tensor. • MOKE characteristic of two sides ribbon is associated to large Barkhausen jumps. [ABSTRACT FROM AUTHOR]

We studied influence of post-processing (annealing and stress-annealing) on domain wall dynamics in Fe-, Ni- and Co-based magnetic microwires with spontaneous and induced magnetic bistability. As-prepared Co-based microwires with low and negative magnetostriction present linear hysteresis loops. Magnetic bistability in Co-based microwires has been induced by annealing. Minimizing magnetoelastic anisotropy either by adjusting the chemical composition with a low magnetostriction coefficient or by heat treatment is an appropriate route for the domain wall dynamics optimization in magnetic microwires. Stress-annealing allows further improvement of domain wall velocity and hence is a promising method allowing optimization of the DW dynamics in magnetic microwires. The beneficial influence of stress-annealing on the DW dynamics is explained considering an increase in the volume of outer domain shell with transverse magnetization orientation in expense of decrease in the radius of the inner axially magnetized core. Such transverse magnetic anisotropy can affect the DW dynamics in similar way as the applied transverse magnetic field and hence is beneficial for the DW dynamics optimization. Thus, stress-annealing allows designing the magnetic anisotropy distribution more favorable for the DW dynamics improvement. Co-rich microwires with magnetic bistability induced by annealing present a considerable enhancement in the DW velocity upon applied tensile stress: exactly the opposite to the case of magnetic microwires with spontaneous magnetic bistability. Observed dependence has been explained considering decrease in the magnetostriction coefficient under effect of the applied stress. Image 1 • Rectangular hysteresis loops of annealed Co-rich microwires. • Tuning of hysteresis loops varying stress-annealing conditions. • Enhancement of domain wall velocity after annealing and stress-annealing. • Enhancement of domain wall velocity by applied stress in Co-rich microwires. • Modification of the magnetic anisotropy distribution by stress-annealing. [ABSTRACT FROM AUTHOR]

The influence of post-processing (annealing and stress-annealing) on the magnetic softness, Giant magnetoimpedance (GMI) effect and domain wall dynamics of Fe 3.6 Co 69.2 Ni 1 B 12.5 Si 11 Mo 1.5 C 1.2 glass-coated microwires is studied. As-prepared Co-rich glass-coated microwire presents linear hysteresis loops and rather higher magnetoimpedance ratio with double-peak magnetic field dependence, typical for materials with transverse magnetic anisotropy. Considerable magnetic hardening and transformation of linear hysteresis loop with low coercivity (H c ≈ 4 A/m) into rectangular with H c ≈ 90 A/m upon annealing without stress is observed. However, we observed remarkable MI effect improvement at certain annealing conditions. Stress-annealing of studied microwire allows considerable magnetoimpedance ratio and domain wall velocity increasing. Additionally, remanent magnetization growth and coercivity decrease are generally observed upon stress annealing. Frequency dependence of maximum GMI ratio for as-prepared and annealed samples is evaluated. The obtained frequency dependence of the maximum GMI ratio allows determination of the optimal GMI measurement conditions for each sample. The observed stress-induced anisotropy and related changes in magnetic properties are discussed considering the internal stresses relaxation and "back-stresses". Image 1 • Magnetic softening of Co-rich microwires after stress-annealing. • Improvement of GMI effect after annealing and stress-annealing in Co-rich microwires. • Fast single domain wall propagation in annealed and stress- annealed Co-rich microwires. • Evolution of the magnetostriction coefficient upon annealing of Co-rich microwires. • Effect of annealing conditions on frequency dependence of maximum MI ratio. [ABSTRACT FROM AUTHOR]