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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]

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]

Studies of magnetic properties and GMI effect of amorphous Co-Fe rich microwires reveal that they present GMI effect at GHz frequencies. Magnetic field dependences of GMI effect are affected by the post-processing conditions. In particular, we observed that in Co-Fe rich microwires stress-annealing allows improvement of frequency dependence of GMI ratio at high frequencies. We discussed observed experimental dependences considering both different magnetic structure and the anisotropy in the bulk and near the surface and close analogy between giant magnetoimpedance and ferromagnetic resonance. [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]

We report on fabrication and magnetic properties of Heusler-type NiMnInCo glass-coated microwires with metallic nucleus diameters, d, from 13 up to 23 μm and total diameters, D, from 47 to 55 lm by the Taylor-Ulitovsky technique. Considerable dependence of magnetization on magnetic field below and in vicinity of Curie temperature can be related with two-phase structure or with the Hopkinson effect. [ABSTRACT FROM AUTHOR]

We observed different kind of defects, such as gas bubbles, glass coating thickness inhomogeneities, indications of the chemical interaction between the glass shell and the metallic nucleus. We showed that the existence of such bubbles might be the origin of the spontaneous fluctuations of the local nucleation field. [ABSTRACT FROM AUTHOR]

We studied magnetic properties and domain wall propagation in Fe77.5-xNixSi7.5B15 (0⩽x⩽77.5) microwires considering effect of applied and internal stresses. We observed rectangular hysteresis loops and fast domain wall propagation for the Fe77.5-xNixSi7.5B15 (0⩽⩽38.75) microwires. We measured dependences of domain wall velocity on applied magnetic field for the Fe77.5-xNixSi7.5B15 microwires with x⩽38.75. In Fe77.5Si7.5B15 and Fe62Ni15.5Si7.5B15 samples, we observed domain wall velocities up to 2.5 km/s. In all studied samples exhibiting fast domain wall propagation, we observed reduction of domain wall velocity under application of tensile stresses. [ABSTRACT FROM AUTHOR]

We report on the magnetic properties of NdFeB powders produced by gas atomization, which is a powder manufacturing technology scarcely used in the past to produce such alloys. Using this technique, we have produced several ternary NdFeB alloys with Nd contents between 26.9 wt.% and 28.5 wt.%. The as-atomized powders were split into different size fractions by sieving. Subsequently, we measured the magnetic properties as a function of temperature, between 10 and 400 K, and particle size. The magnetic behavior depends strongly on the microstructure of the material, which in turn is determined by the particle size. It is reported a slope anomaly in the curve of magnetization as a function of temperature at around 150 K due to a spin-reorientation transition. Since gas-atomized powders are isotropic, this magnetic transition produces an increment of the magnetization below this temperature. [ABSTRACT FROM AUTHOR]

We have prepared Fe-Pt and Fe-Pt- M (M = B, Si) microwires using Taylor-Ulitovsky technique and studied their magnetic properties. Magnetic properties considerably depend on the metallic core composition and annealing conditions. As-prepared microwires present either amorphous or mixture of amorphous and nanocrystalline phases with a presence of BCC FePt, FCC PtFe and small amount of tetragonal FePt phase. After annealing at 500 °C Fe 50 Pt 40 Si 10 microwires we observed a remarkable magnetic hardening (coercivity increasing from 5 Oe up to 500 Oe) related to crystallization of as-prepared amorphous Fe 50 Pt 40 Si 10 microwires. Annealed Fe 50 Pt 50 sample present coercivity up to 800 Oe at 5K, but the magnetization of Fe 50 Pt 50 sample is low and rapidly decreases with temperature. We discussed peculiarity of Fe 50 Pt 50 microwires considering the influence of internal stresses on magnetic ordering of Fe-atoms. [ABSTRACT FROM AUTHOR]

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

We studied the effect of annealing on magneto-transport, magnetic, and structural properties of CuCo ( x = 5, 10, 20) glass-coated microwires prepared using the Taylor-Ulitovsky technique. Both as-prepared and annealed samples exhibit magnetoresistance effect. We observed a Kondo-like effect in as-prepared and annealed CuCo microwire and a significant increase of the giant magnetoresistance (GMR) in all studied Co-Cu after annealing. The origin of GMR effect and Kondo-like behavior is discussed considering structural changes of the annealed samples. [ABSTRACT FROM AUTHOR]

We have studied Hitperm-type and Finemet-type glass-coated microwires with a nanocrystalline structure. In Hitperm-type microwires where the nanocrystalline structure has been obtained directly after melt quenching using the Taylor-Ulitovsky fabrication technique, we observed rectangular hysteresis loops and studied the domain wall propagation. We measured and analyzed the switching field dependence on the frequency in as-prepared and annealed Hitperm-type microwires. A conventional annealing results in a drastic change of the frequency dependence of the switching field. This effect might be interpreted considering the stress relaxation process. We have also studied the correlation of magnetic properties, structure, and giant magnetoimpedance (GMI) effect in Finemet-type FeCuNbSiB microwires prepared by the Taylor-Ulitovsky technique. We observed that both GMI effect and magnetic softness of Finemet-type glass-coated microwires can be tailored by heat treatment, and after annealing a considerable magnetic softening of studied samples has been achieved. This magnetic softening correlates well with the devitrification of amorphous samples. Amorphous Fe-rich microwires exhibit a low GMI effect (GMI ratio below 1%). A considerable enhancement of the GMI effect (GMI ratio up to 100%) has been observed in heat-treated microwires developing a nanocrystalline structure. [ABSTRACT FROM AUTHOR]

We studied giant magnetoimpedance (GMI) effect, magnetic, and magneto-optic properties of Finemet-type FeCuNbSiB microwires. We observed that GMI effect and magnetic softness of glass-coated microwires produced by the Taylor-Ulitovsky technique can be tailored either controlling magnetoelastic anisotropy of as-prepared FeCuNbSiB microwires or controlling their structure either by heat treatment or changing the fabrication conditions. We observed considerable magnetic softening of studied microwires after annealing. This magnetic softening correlates with the devitrification of amorphous samples. Amorphous Fe-rich microwires exhibited low GMI effect (GMI ratio below 1 %). Considerable enhancement of the GMI effect (GMI ratio up to 100 %) has been observed in heat-treated microwires with nanocrystalline structure. Some of as-prepared Fe-rich magnetic microwires exhibited nanocrystalline structure and GMI ratio up to 45 %. The magneto-optical study demonstrated the existence of helical surface magnetic structure in the as-prepared microwires. [ABSTRACT FROM AUTHOR]

Ribbons of composition Co49Ni21Ga30 have been prepared by melt-spinning method. X-ray diffraction investigation revealed single phase with B2 structure at room temperature. However, analysis of magnetization dependence of temperature suggests phase transition in the range 150-250 K. Resistivity measurements revealed similar transition with shift to higher temperatures in the presence of magnetic field. [ABSTRACT FROM AUTHOR]

We report on the magnetic, transport and structural properties of Cox-Cu100-x (5=x=40) glass-coated microwires. For x=5 we observed the resistivity minimum at 40 K associated with the Kondo effect. For x = 10 we observed considerable magnetoresistance effect. Temperature dependence of susceptibility show considerable difference for x>10 and x= 10 attributed to the presence of small Co grains embedded in the Cu matrix f or x = 1 0. U sing X -ray diffraction we found, that the structure of Cox-Cu100-x microwires x = 10 is granular consisting of two phases: fcc Cu appearing in all the samples and fcc a-Co presented only in microwires with higher Co content. [ABSTRACT FROM AUTHOR]

We studied giant magneto-impedance (GMI) effect, magnetic and structural properties of thin Finemet-type (FeCuNbSiB) glass-coated microwires fabricated by Taylor-Ulitovsky technique with different composition and diameters, with the aim to achieve the optimal conditions for improving the final GMI response. We observed that GMI can be tailored either by controlling the microwires microstructure through the thermal annealing, or by controlling the quenching rate velocity during the fabrication processes. Finally, we obtained up to 50% GMI in the as-prepared samples and up to 100% in annealed microwires. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

We studied GMI effect and magnetic properties of Finemet-type FeCuNbSiB microwires. We observed that GMI magnetic field and frequency dependences and magnetic softness of composite microwires produced by the Taylor-Ulitovski technique can be tailored either controlling magnetoelastic anisotropy of as-prepared FeCuNbSiB microwires or controlling their structure by heat treatment or changing the fabrication conditions. GMI effect has been observed in as-prepared Fe-rich microwires with nanocrystalline structure. [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]

Abstract: In this paper, we present the giant magneto-impedance (GMI) effect (real part of longitudinal impedance, Z, and of the off-diagonal impedance) and hysteretic magnetic properties of amorphous glass-coated microwires with different compositions possessing nearly zero, positive and negative magnetostriction constant and metallic nucleus diameter ranging between 6 and 16μm. Enhanced soft magnetic properties (low coercivity of about 4A/m) and high-GMI effect have been observed in Co-rich microwires with vanishing magnetostriction constant. The magnetic anisotropy field of these microwires depends on the ratio between metallic diameter, d and total microwires diameter, D. Stress-sensitive magnetic properties have been obtained in Fe-rich microwires after stress annealing: hysteresis loop stress-annealed (SA) microwires drastically changes under applied stress. A variety of hysteresis loops with different hysteresis loops can be obtained in Fe-rich microwires changing the conditions (time and/or temperature) of the stress annealing. The obtained results allow us to tailor the microwire magnetic properties for magnetic sensors applications through selection of their composition and/or geometry and by thermal treatment. [Copyright &y& Elsevier]

Abstract: In this paper we report novel results on the fabrication and magnetic characterization of microwires with compositions Co100− x –Fe–Ni x –Si–B and Co–Fe–Cr–Si–B fabricated by Taylor–Ulitovsky. Additions of Ni or Cr resulted in decreasing of the Curie temperature, T C. Few samples with low T C possessing also high GMI effect are obtained. Concrete temperature sensors applications based on the drastic change of magnetic properties in the vicinity of Curie temperature are shown. [Copyright &y& Elsevier]

In this work we studied influence of time and temperature of stress annealing on magnetic properties of amorphous Co-based and CoFeNi-based microwires. We showed that this type of treatment can be very effective for manipulation of magnetic properties of amorphous ferromagnetic glass-coated microwires. Co-based microwires keep S-shape hysteresis loop after any annealing. Annealing of Co-based microwires at different conditions allows tailoring of the saturation field. CoFeNi-based microwires present either S-shape or rectangular shape of the hysteresis loops depending on the value of the axial stress during the annealing. We demonstrated the possibility to change the switching field of microwires with acquired bistability in the range from 0.5 to 25 A/m. [ABSTRACT FROM AUTHOR]

We present studies of the temperature dependence of AC susceptibility, χ, and magnetization, M in few Fe-Cr based microwires. We observed drastic increasing of the χ in vicinity of Curie temperature which we interpreted as the Hopkinson effect. Cr content drastically affects the Curie temperature of studied microwires. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

Structural characterization (differential scanning calorimetry, DSC, and X-ray diffraction, XRD) and temperature dependence of the magnetization are reported in Ni 80 Si 10 B 10 and Ni 75 Si 15 B 10 alloy ribbons produced by rapid solidification. XDR and DSC measurements lead to confirm the amorphous character of Ni 75 Si 15 B 10 alloy while the Ni 80 Si 10 B 10 alloy presents a mixture of amorphous and crystalline (Nickel face-centered cubic) phase. Low-temperature magnetization dependencies were analyzed in terms of spin-wave excitation and fluctuations of the exchange interaction. While both mechanisms are relevant for the high Ni-content alloy, fluctuations of exchange could be ascribed as mechanism for low Ni-content alloy. The effect of annealing (523 and 623 K during 1 h) on the magnetic behavior is also presented. Thus, annealing of Ni75 sample at 623 K also results in appearance of highly magnetic Ni phase. [ABSTRACT FROM AUTHOR]

We studied the effect of annealing on the magnetic properties and domain wall (DW) dynamics of magnetically bistable, Fe-based, glass-covered microwires with two different compositions, and different diameters. We observed the correlation of the domain wall dynamics with the distribution of the nucleation fields, measured in as-prepared samples, and after annealing for up to 150 min at temperatures of 250 and 300 °C. We found that both DW velocity and the range of the field limiting the single DW dynamics changed after annealing. [ABSTRACT FROM AUTHOR]

Abstract: We have applied the measurement of the amplitude dependence of the complex AC susceptibility to study the magnetization processes in amorphous glass-coated microwires with positive, negative and vanishing magnetostriction. The features of the magnetization process (reversible domain wall movement, irreversible domain wall movement, reversible magnetization rotation or irreversible magnetization rotation) can be recognized from the shape of the amplitude dependence of complex AC susceptibility, which confirms the domain structures predicted in microwires with different magnetostriction constant. [Copyright &y& Elsevier]

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]

We studied magnetic properties and GMI effect of Finemet-type FeCuNbSiB microwires. We observed that GMI effect and magnetic softness of microwires produced by the Taylor-Ulitovski technique, can be tailored by either controlling magnetoelastic anisotropy of as-prepared FeCuNbSiB microwires or controlling their structure by heat treatment or changing the fabrication conditions. GMI effect has been observed in as-prepared Fe-rich microwires with nanocrystalline structure. [ABSTRACT FROM AUTHOR]

We studied magnetic properties and GMI effect of Finemet-type FeCuNbSiB microwires. We observed that GMI effect and magnetic softness of microwires produced by the Taylor-Ulitovski technique, can be tailored by either controlling magnetoelastic anisotropy of as-prepared FeCuNbSiB microwires or controlling their structure by heat treatment or changing the fabrication conditions. GMI effect has been observed in as-prepared Fe-rich microwires with nanocrystalline structure. [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]

The effect of cobalt doping on martensitic transformations and the magnetic properties of Ni 50−x Co x Mn 37 Sn 13 (x = 1, 2, 3) magnetic shape memory alloys obtained by melt spinning in the form of ribbons is studied. The crystallographic structure of all of the ribbons at room temperature is austenite cubic L2 1 . SEM micrographs indicate the formation of textured ribbons with columnar grains growing up perpendicular to the ribbon plane. For all of the ribbons, DSC cyclic scans reveal the martensitic transformation on cooling and the reverse austenitic transformation upon heating below room temperature. In addition, they indicate that the martensitic transformation temperatures decrease with an increasing cobalt content. Thermomagnetic curves reveal the coexistence of AFM and FM exchange interactions at low temperatures. Likewise, the magnetization change (Δ M ) between the martensite and austenite phase, as well as the austenite Curie temperature ( T C A ), increase with increasing cobalt content in the ribbons. Structural transformations are also sensitive to the external applied magnetic field. This fact suggests that the structural transformation temperatures of the ribbons could be tuned to the desired functional temperature by controlling the cobalt amount through the replacement of Ni as well as by changing the applied magnetic field, which could lead to an enhancement of the magnetic properties. [ABSTRACT FROM AUTHOR]

We present comparative studies of magnetic properties and giant magnetoimpedance (GMI) effect of Fe and Co-rich microwires. As-prepared Co-rich microwires present much higher GMI ratio. The impact of the stress-annealing on magnetic softness and high frequency magnetoimpedance effect of Fe-rich microwires has been studied. The large improvement of the magnetoimpedance response in a wide frequency range by the stress-annealing is observed. We have achieved GMI ratio increase by an order of magnitude after stress-annealing of Fe-rich microwire. Observed stress-induced anisotropy and related changes of magnetic properties are discussed considering internal stresses relaxation and “back-stresses”. [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]

Abstract: We studied giant magnetoimpedance (GMI) effect and magnetic properties of Fe70.8Cu1Nb3.1Si14.5B10.6 and Fe71.8Cu1Nb3.1Si15B9.1 Finemet microwires. We observed that GMI effect and magnetic softness of glass-coated microwires produced by the Taylor–Ulitovski technique can be tailored either controlling magnetoelastic anisotropy of as-cast FeCuNbSiB microwires, and/or controlling their structure by heat treatment or by changing the fabrication conditions. High GMI effect has been observed in as-prepared Fe-rich and heat treated microwires with nanocrystalline structure. [Copyright &y& Elsevier]

Abstract: A novel family of magnetic materials, thin ferromagnetic metallic glass-coated wires (1/30μm in diameter) produced by the Taylor–Ulitovsky method present excellent magnetic properties such as magnetic bistability, GMI effect or enhanced magnetic softness attracting great attention for sensor applications. In this paper we report novel results on the fabrication and magnetic characterization of a number of Co–Fe–Ni–Si–B and Co–Fe–Cr–Si–B microwires with total diameter between 15 and 37μm fabricated by the Taylor–Ulitovsky method with low Curie temperature possessing also good magnetic softness and high GMI effect. Magnetization, hysteresis loops, magnetic susceptibility and their magnetic field dependence and GMI effect at frequencies up to 500MHz have been measured. Few samples possessing low T C (below 100°C) also present high GMI effect with GMI ratio achieving 110% at 100MHz. Additions of Ni or Cr to the conventional Co–Fe–Si–B composition with vanishing magnetostriction constant resulted in significant decreasing of the Curie temperature. Concrete applications have been designed such as the temperature sensors applications based on drastic change of the magnetic properties in the vicinity of Curie temperature. [Copyright &y& Elsevier]

Abstract: Different kinds of magnetic anisotropies have been induced during the nanocrystallization process of Co- and Ni-rich amorphous ferromagnetic (Finemet) ribbons using diverse procedures like the application of a constant stress or an axial magnetic field during the annealing process. Magnetization measurements have evidenced the anisotropy of the treated samples. The main goal of this work has been the structural and microstructural analysis of the treated ribbons using X-ray Diffraction (XRD) and Atomic Force Microscopy (AFM), detecting substantial differences in the crystallization state and grain size of the samples depending on the treatment that was carried out. Moreover, AFM measurements revealed in all the treated samples a strong nanocrystallization of the surface without evidences of amorphous matrix, which contrast with XRD measurements that have shown a high content of amorphous phase in the bulk of the ribbons. Magneto-optical Kerr effect measurements have been performed with the aim to elucidate the complex magnetic behavior that is expected for the surface of the ribbons, measuring surface hysteresis loops that show much higher coercive field values than in the bulk. [Copyright &y& Elsevier]

• 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]

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]

Herein, the temperature dependence of hysteresis loops and the Giant magnetoimpedance, GMI, effect of amorphous as-prepared and stress-annealed FeSiBC microwires have been thoroughly analyzed. We observed a remarkable improvement of GMI ratio and modification of hysteresis loops from rectangular to inclined with increase in temperature for as-prepared FeSiBC microwires. Observed changes have almost completely reversible character. On the other hand, rather different behavior is observed in stress-annealed FeSiBC microwires: a substantial GMI ratio improvement is observed in stress-annealed FeSiBC microwires. However, a decrease in GMI effect is observed with temperature increasing. Observed experimental results are discussed considering relaxation of internal stresses upon heating, Hopkinson effect and modification of the thermal expansion coefficients upon heating. • Strong temperature dependence of hysteresis loops and Giant magnetoimpedance effect of Fe 75 B 9 Si 12 C 4 glass-coated microwires. • Almost complete reversibility of the hysteresis loops and GMI effect modification upon heating of as-prepared FeBSiC microwires. • Substantial improvement of the GMI ratio with increase in temperature for as-prepared FeSiBC microwires. • Temperature dependence of the GMI effect in Fe-rich microwires useful for temperature monitoring. [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 magnetic properties of Fe 38.5 Co 38.5 B 18 Mo 4 Cu 1 Hitperm-like glass-coated microwires obtained by Taylor-Ulitovsky technique with nanocrystalline structure consisting of about 20–30 nm BCC α-FeCo and an amorphous precursor in as-prepared samples. We observed a considerable decrease of the average grain size (from about 23 to 11 nm) after annealing. As-prepared and annealed Fe 38.5 Co 38.5 B 18 Mo 4 Cu 1 Hitperm-like glass-coated microwires present rectangular hysteresis loops and fast domain wall propagation. We measured and analyzed the frequency dependence of the switching field dependence and domain wall dynamics in as-prepared and annealed Hitperm-type microwires. Obtained results are discussed in terms of the microstructural relaxation, grains refinement and internal stresses relaxation. An enhancement of the domain wall velocity as well as mobility after annealing has been attributed to the structural relaxation of such grains with positive magnetostriction. [ABSTRACT FROM AUTHOR]

In the current study, we have succeeded to fabricate Co 2 FeSi Heusler alloy glass-covered microwires with magnetic core nucleus diameter d = 4.36 µm and total diameter D = 17.55 µm, with high Curie temperature (T c >1100 K) and well-defined magnetic anisotropy for high temperature spintronic devices application. The magnetic properties of as-prepared and annealed at different temperature (873 K, 973 K and 1073 K for 1 h) of Co 2 FeSi Heusler alloy glass-covered microwires have been investigated. Strong dependence of the magnetic properties on the annealing conditions has been indicated. Anomalous magnetic behavior for annealed samples at 873 K and 973 K has been found and structural properties of such samples have been analyzed. Critical temperatures 155 K and 250 K have been detected for annealed samples at 873 K and 973 K, respectively, where the behavior of M-H loops and coercivity changed. Below the critical point the M-H curve shows "kink or wasp-waisted" magnetic behavior and complex magnetic reversal mechanism is supposed. The anomalous magnetic behavior is due to the martensitic phases induced by annealing conditions below the room temperature. This unusual magnetization behavior provides opportunities to understand the phenomena of different types of magnetic domain structures in the preferred crystallographically oriented Co 2 FeSi Heusler alloy glass-coated micro-wires, essentially helpful for designing the devices based on magnetization switching. • Production of Co 2 FeSi Heusler alloy glass-coated microwires with high Curie temperature. • Strong dependence of the magnetic properties Co 2 FeSi Heusler alloy glass-coated microwires on the annealing conditions. • Anomalous magnetic behavior below the room temperature for Co 2 FeSi glass-coated microwires annealed at 873 K and 973 K. • Critical temperatures where changes in the magnetic and structure phases appear were detected for annealed samples. • Suitability of Co 2 FeSi microwires for the design of devices based on magnetization switching. [ABSTRACT FROM AUTHOR]

We have employed melt-spinning method to produce Ni 2 MnSn-based half-metallic Heusler alloy. It allows fast and simple production of large amount of materials in a single production step avoiding high temperature post-production annealing. Microstructural, magnetic and spin polarization study of Ni 2 MnSn ribbon is used for characterization. SEM analysis reveals the polycrystalline structure with the columnar crystals grown perpendicularly to the ribbon plane. A single-phase austenite with L2 1 structure was confirmed by X-ray. Magnetic measurements shows the ordinary ferromagnetic behavior with Curie temperature 344 K and magnetic moment 4.08 µ B /f.u. Particular crystal structure leads to the well defined anisotropy having an easy plane in the ribbon's plane. Finally, the spin polarization parameter P 0 estimated by Point-Contact Andreev-reflection Spectroscopy is varying in the range 40–70% for Ni 2 MnSn which is comparable with other values reported earlier for other Heusler alloys. [ABSTRACT FROM AUTHOR]

We demonstrated that magnetic properties (hysteresis loops, domain wall propagation and giant magnetoimpedance effect) of Fe and Co-rich amorphous microwires can be tailored by stress and conventional annealing. Observed dependences discussed considering stress relaxation, back stresses and change of the magnetostriction after samples annealing. These considerations have been proved by experimental observation of the change of the magnetostriction coefficient sign induced by annealing. [ABSTRACT FROM AUTHOR]

Highlights: [•] Preparation of Ni–Mn–In Heusler alloys by melt spinning technique in ribbon shape. [•] Short annealing effects on the crystal structure, microstructure and magnetic properties. [•] Influence of annealing on the martensitic transformation. [•] Enhancement of the exchange bias effect. [ABSTRACT FROM AUTHOR]

Abstract: Magnetic anisotropy has been induced during the nanocrystallization process of Ni-rich amorphous ferromagnetic (Finemet) ribbons by means of the application of a constant stress during the annealing process. Magnetization measurements have evidenced the anisotropy of the treated samples. The main goal of this work was the analysis of the treated ribbons using X-ray Diffraction (XRD), Transmission Electronic Microscopy (TEM) and Atomic Force Microscopy (AFM). AFM measurements revealed in all the cases a strong nanocrystallisation of the surface without evidences of amorphous matrix, which contrast with XRD and TEM measurements that have shown a high content of amorphous phase in the bulk of the ribbons. Magneto-optical Kerr effect measurements show much higher coercive field values than in the bulk, indicating a complex magnetic behavior for the surface of the ribbons. [Copyright &y& Elsevier]

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]

Herein, by using both hysteresis loops and the Giant magnetoimpedance, GMI, measurements, the magnetic properties of amorphous FeSiBC microwires have been thoroughly analyzed paying attention on the influence of annealing (under stress or without stress) on the GMI effect and magnetic properties of Fe–Si–B–C microwires. We observed that stress annealing allows the induction of transverse magnetic anisotropy and the GMI effect improvement. This stress-annealing induced anisotropy depends on the stress-annealing conditions: annealing time and stress applied during the annealing and can be partially annealed out by subsequent furnace annealing. However, the reversibility of the stress-annealing induced anisotropy depends on the stress-annealing conditions. Particularly, most of the transverse induced magnetic anisotropy obtained by stress-annealing at high stresses values is irreversible. Stress-annealing followed by annealing without stress allows further improvement of the GMI effect in Fe–Si–B–C microwires in a wide frequency range. Coercivity, remanent magnetization, and magnetoimpedance ratio of FeSiBC microwires can be tuned by annealing conditions: annealing time and stress. All studied microwires present GMI hysteresis. The sample with the highest GMI ratio presents the lowest GMI hysteresis. Observed experimental results are discussed considering relaxation of internal stresses, compressive "back-stresses" arising after stress annealing and topological short range ordering. Image 1 • Considerable enhancement of the GMI effect by subsequent annealing of stress-annealed Fe-based microwires. • Growing contribution of irreversible stress-annealing induced anisotropy with increasing stress applied during the annealing. • Stress-annealing induced anisotropy affected by annealing time and stress applied during the annealing. • Correlation of the GMI hysteresis observed in as-prepared and annealed microwires and the GMI ratio. • Interpretation of induced anisotropy considering stress relaxation, back stresses and topological short range ordering. [ABSTRACT FROM AUTHOR]