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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]

We observed that stress-annealing of Fe75B9Si12C4 magnetic microwire at variable annealing temperature allows to create graded magnetic anisotropy. We have found that single domain wall (DW) propagation in a media with graded magnetic anisotropy is essentially non-uniform: faster DW propagation is observed in the region with moderate stress-annealing induced magnetic anisotropy. Higher DW velocity in the region with induced magnetic anisotropy is explained by the transverse character of stress-annealing induced magnetic anisotropy which affects the travelling DW in a similar way as application of transversal bias magnetic field. Obtained graded magnetic anisotropy allows engineering the DW dynamics of Fe-rich microwires. [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 investigated the effects of induced helical anisotropy and application of dc bias current IB on longitudinal magnetoimpedance (MI) in amorphous microwires both separately and together. We demonstrated that when both parameters are present, i.e., a dc bias current IB is applied to the microwire with induced helical anisotropy, the longitudinal MI sensor range can be considerably extended up to the fields considerably higher than its anisotropy field as the slope of MI curve dZ/dHE remains rather high. A highly asymmetric longitudinal MI dependence with a rather high slope at the zero-field point was obtained. Reversing the bias current IB causes reversal of the bias field direction and results in a mirroring of the MI dependence. This gives a possibility to determine both the sign and the magnitude of the external magnetic field. The obtained results can be used in development of the longitudinal MI sensors with increased sensitivity and/or range. [ABSTRACT FROM AUTHOR]

A magnetic field tunable electromagnetic response in periodic lattices of conducting magnetic wires is demonstrated. The wire medium having a negative permittivity in the lower frequency band is customarily investigated as an important component of so-called double negative metamaterials. Here we are interested in a strong dispersion of the permittivity in these structures and a possibility to alter it by changing the losses in magnetic wires with an external magnetic field. The theoretical approach is based on calculating the relaxation parameter depending on the wire surface impedance, and hence, on the wire magnetic properties. Thus, in arrays of Co-based amorphous wires the application of a moderate magnetic field (of about 1-2 kA/m) which causes the magnetization reorientation is capable of few fold permittivity change in the frequency range of 1-2 GHz. Such efficient tuning for certain structural and magnetic parameters was confirmed experimentally by measuring the transmission and reflection spectra from lattices of Co66Fe3.5B16Si11Cr3.5 glass-coated amorphous wires with a different wire cross-section and a different lattice period. The chosen wires are also confirmed to show a large magnetoimpedance effect at GHz frequencies, which constitutes the underlying mechanism of magnetic field dependent permittivity in wire media. [ABSTRACT FROM AUTHOR]

Two magnetization reversal regimes were found in magnetically bistable Fe-rich microwires. The first one, exhibiting an almost linear dependence of the domain wall velocity v on magnetic field H reaching 1.7 km/s, is related to single DW propagation. The second essentially nonlinear regime is observed when H exceeds some critical magnetic field, HN, determined by the microwire inhomogeneities. At H>HN, new reverse domains can be nucleated, and consequently a tandem remagnetization mechanism can be realized. Ultrafast magnetization switching through additional nucleation centers created artificially can be applied in spintronic devices for enhancing their performance. [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 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 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 have investigated the effect of dc bias current IB on longitudinal magnetoimpedance (MI) in amorphous microwire with helical anisotropy and experimentally demonstrated that, by changing the dc current IB, it is possible to considerably affect the MI dependence. We propose to use this effect in developing a longitudinal MI sensor that overcomes the drawbacks usually associated with the longitudinal MI-namely the impossibility to determine the direction of an external axial magnetic field HE and the low sensitivity near the zero-field point. We demonstrate that a set of two measurements of longitudinal wire impedance with properly selected bias current IB allows determination of both the magnitude and direction of the magnetic field HE over an extended range, much higher than the sample anisotropy field. Additional features of the proposed method are the increased sensitivity and the detection of exceeding the operating range. [ABSTRACT FROM AUTHOR]

We studied the magnetic properties and domain wall (DW) dynamics of Fe47.4Ni26.6Si11B13C2 and Fe77.5Si7.5B15 microwires. Both samples present a rectangular hysteresis loop and fast magnetization switching. The linear region of dependence of the DW velocity on the magnetic field in Fe47.4Ni26.6Si11B13C2 sample is considerably shorter. Consequently, we studied the structure of Fe47.4Ni26.6Si11B13C2 sample using X-ray diffraction and atom probe tomography. The results obtained using the atom probe tomography supports the formation of B-enriched precipitates in the interfacial layer and in the metallic nucleus after annealing. [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 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]

Abstract: We have studied the effect of the internal circumferential magnetic field H B created by the dc bias current I B on longitudinal and off-diagonal magnetoimpedance (MI) in amorphous microwire with helical anisotropy and experimentally demonstrated that by changing the dc current I B it is possible to considerably change the MI dependencies. The bias current applied to such microwire transforms the symmetric and hysteretic MI curve to asymmetrical and anhysteretic. The minimum of longitudinal MI curve shifts from the zero-field point. Reversing the bias current causes reversal of the bias field direction and results in a mirroring of the MI curves. It is proposed to apply a cross-checking of two MI curves with I B of different polarity for magnetic field sensing. In particular, this method allows to overcome the drawbacks usually associated with longitudinal MI—namely the impossibility to determine the direction of an external axial magnetic field H E and the low sensitivity near the zero-field point. Moreover, the operating range of the longitudinal MI sensor, in contrast to the off-diagonal one, can be much extended as it exhibits a quite high sensitivity in the field range up to one order of magnitude higher than the anisotropy field. [Copyright &y& Elsevier]

We studied magnetic, transport and structural properties of granular Cox-\rm Cu100-{\rm x} glass-coated microwires. Co-Cu microwires exhibited considerable magnetoresistance (MR) effect. For x=5\% we observed the resistivity minimum at 40 K associated with the Kondo effect. For x>10 partial evidences of granular structure have been observed. Temperature dependence of magnetization measured in microwires Cox-\rm Cu100-{\rm x} with x\geq 10 during a cooling regime without external magnetic field (ZFC) and in the presence of the field (FC) show considerable difference at low temperatures, attributed by us with the presence of small Co grains embedded in the Cu matrix. By X-ray diffraction we found, that the structure of the metallic nucleus is granular consisting of two phases: fcc Cu appearing in all the samples and fcc \alpha-Co presented only in microwires with higher Co content. For low Co content (x\leq 10\%) XRD magnetic and magneto-transport measurements indicate that Co atoms and small Co clusters are distributed within the Cu crystals. [ABSTRACT FROM PUBLISHER]

Smart composites with short-cut Co68.7Fe4Ni1B13Si11Mo2.3 microwires were prepared and studied in terms of their microwave tunable properties. It is shown that the frequency dependence of effective permittivity relaxes with the application of magnetic field till around the anisotropy field of the microwire due to the increase of internal losses. There exists a significant field tunable effect in the transmission and reflection spectra, featured as a resonance-relaxation transformation; a step-like shift of reflection phase was also observed with increasing applied magnetic field, which can be exploited especially for the sensing applications such as field/stress monitoring. Notably, with increasing microwire concentration from 0.06 cm^-2 to 0.24 cm^-2, the microwave absorption is more than doubled; the reflection phase shift corresponding to the magnetic field change from 500 to 1000 A/m is also increased from 1.2 to 1.3. These results indicate that the developed short-wire composites have the potential for microwave absorption and remote sensing applications. [ABSTRACT FROM AUTHOR]

This paper discusses a new type of wire media based on amorphous ferromagnetic microwires. The combination of two effects, namely, a strong dispersion of the effective permittivity in metallic wire composites (resonance or plasmonic type) and giant magnetoimpedance effect in wires, will result in unusual property that an effective dielectric response may strongly depend on the wire magnetization which can be changed with external stimuli: magnetic field, mechanical stress and temperature. [ABSTRACT FROM AUTHOR]

The effect of the external magnetic field on the dispersion of the effective permittivity in a single array of parallel CoFe-based amorphous wires is demonstrated by measuring the transmission/reflection spectra in free space in the frequency band of 0.9-17 GHz. The magnetic field is applied along the wires, sensitively changing their magnetisation and high-frequency impedance. Based on the measurements of magneto-impedance in a single wire and S-parameters of composites in free space, we show the correlation between the magneto-impedance and the field dependence of the effective permittivity. [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]

We are trying to reveal the contribution of local defects on DW propagation in amorphous microwires. Consequently, we present a comparative study of single domain wall dynamics and local nucleation fields in Fe- and Co-rich amorphous glass-coated microwires. For this we modified experimental set-up based on the classical Sixtus-Tonks approach introducing additional pick-up coil in order evaluate defects contribution in domain wall propagation. Below some critical magnetic field, H, determined by the microwires inhomogeneities, an almost linear DW velocity, v, dependence on magnetic field, H, is found. Quite fast DW propagation ( v till 3000 m/s at H about 65 A/m) has been observed. When the applied magnetic field exceeds H, new reverse domains can be nucleated and consequently tandem remagnetization mechanism can be realized. The role of defects existing in magnetically bistable microwires is related with nucleation of new reversed domains. [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]

Magnetoimpedance (MI) response in the frequency range of 10–1000 MHz of Co69 Fe4 Si15 B12 amorphous ribbons obtained by rapid solidification without and with a magnetic field of 56 kA/m applied in the transverse direction of the ribbon during the fabrication is reported. MI of the ribbon produced without magnetic field presents one-peak behaviour at low frequency (<50 MHz) emerging two-peaks above this frequency, while the two-peaks is present at all frequencies for the ribbon produced with magnetic field as a consequence of the transverse magnetic anisotropy induced during the fabrication process. The evolution of the maximum of MI with the axial magnetic field, ascribed to the anisotropy field, as a function of the frequency provides useful information on the ribbons magnetic inhomogeneity through their cross section. [ABSTRACT FROM PUBLISHER]

Experimental results of the magnetic field driven domain walls dynamics in magnetically bistable Fe-rich microwires are reported. We have observed that under certain conditions a controllable domain wall (DW) collision can be realized in different parts of the wire, and that it is possible to manipulate the DW dynamics in a field-driven regime. The DW collisions obtained in this way can be used to release pinned domain walls. We have also found a correlation between the local nucleation field distribution and field dependence of DW velocity: the magnetic field value corresponding to the minimum nucleation field determines a threshold between single and multiple domain wall propagation regimes. [ABSTRACT FROM AUTHOR]

We have investigated the impedance dependence of magnetically soft microwire on the internal circumferential magnetic field HB created by the dc bias current IB and theoretically and experimentally demonstrated that in a conductor with helical magnetic anisotropy, the high frequency impedance depends on the dc bias current IB (or the corresponding bias field HB) and this dependence is hysteretic. We have experimentally observed a change of impedance more than 35% upon changing the bias current. The possible applications of the dc current-driven magnetoimpedance effect are discussed. [ABSTRACT FROM AUTHOR]

Abstract: In this paper we report novel results on the GMI effect at frequencies between 10MHz and 500MHz in ultra-thin Co–Fe-rich amorphous glass-coated microwires with nearly zero magnetostriction constant with metallic nucleus diameter of about 8.5μm. At 10MHz the GMI of thin microwires is smaller than in thicker conventional wires and glass-coated microwires, but increasing the frequency GMI effect significantly increases, exhibiting much higher GMI effect at high frequencies and the shape of the dc magnetic field dependence of the GMI ratio is typical for the materials with circular magnetic anisotropy, i.e. with the a maximum at certain dc axial magnetic field. Besides, the glass-coating technology gives rise to the internal stresses due to the difference in the thermal expansion coefficients of the glass coating and metallic nucleus. This difference in the fabrication technique results in the different magnetic anisotropy in the surface and in different frequency dependence of the GMI effect. [Copyright &y& Elsevier]

In this paper, we present the results on giant magneto-impedance (GMI) effect in thin microwires at frequencies until 4 GHz, paying special attention to tailoring the GMI effect and achievement of low hysteretic GMI behavior. Correlation between magnetoelastic anisotropy and magnetic field dependences of diagonal and off-diagonal impedance components are observed. We found that, if the surface anisotropy is not circumferential, then the magnetization and, consequently, the magnetic field dependence of impendence present hysteresis. Low field GMI hysteresis, has been suppressed by the bias current. [ABSTRACT FROM AUTHOR]

We report the results of a systematic study on stress tunable absorption of glass-coated amorphous Co68.7Fe4Ni1B13Si11Mo2.3 microwires and their composites. The magnetic microwires possess good stress-impedance properties and yield a stress dependence of absorption at gigahertz frequencies. The stress compensates the reverse effect of magnetic field on absorption. There exist strong stress dependences of the effective permittivity and transmission parameters. Composite failure due to the wire damage results in a dramatic change of the sign and magnitude of effective permittivity. The double peak is identified in the stress dependence of field tunability, in contrast to the single peak for the magnetic field tunability. All these results indicate that the present composites are very promising for detecting the ambient stress levels and interrogating the structural integrity. [ABSTRACT FROM AUTHOR]

We observed a remarkable improvement of domain wall (DW) mobility, DW velocity, giant magnetoimpedance (GMI) effect and magnetic softening at appropriate stress-annealing conditions. Beneficial effect of stress-annealing on GMI effect and DW dynamics is associated with the induced transverse magnetic anisotropy. An improvement of the circumferential permeability in the nearly surface area of metallic nucleus is evidenced from observed magnetic softening and remarkable GMI effect rising. We assumed that the outer domain shell with transverse magnetic anisotropy associated to stress-annealing induced transverse magnetic anisotropy affects the travelling DW in a similar way as application of transversal bias magnetic field allowing enhancement the DW velocity. Observed decreasing of the half-width of the EMF peak in stress-annealed microwires can be associated to the decreasing of the characteristic DW width. Consequently, stress annealing enabled us to design the magnetic anisotropy distribution beneficial for optimization of either GMI effect or DW dynamics. [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]

Abstract: We present the results on tailoring of soft magnetic properties and GMI effect in thin microwires paying special attention on achievement of low hysteretic high GMI effect in the extended frequency range (up to 4GHz). We observed considerable dependence of the GMI ratio and magnetic anisotropy field, Hk , of Co-rich amorphous microwires with vanishing magnetostriction constant on the internal and applied stresses. For low magnetostrictive Co-rich composition we obtained microwires low coercivity values (generally below 10A/m). Field dependence of the off-diagonal voltage response measured in pulsed regime (pulsed GMI) exhibits anti-symmetrical shape. The magnetic anisotropy of Co and Fe-rich microwires can be tailored by stress or magnetic field annealing. Particularly stress annealed Fe-rich microwires exhibit stress-sensitive GMI effect and hysteretic properties. Varying the time and the temperature of such stress annealing we are able to tailor both magnetic properties and GMI. Additionally, magnetic response of linear microwires arrays and GMI effect of the system containing few microwires can be tailored through the magnetostatic interaction between the microwires. We found, that if the surface anisotropy is not circumferential, then the MI curve Z(H) presents hysteresis. This hysteresis can be suppressed by application of sufficiently high DC bias current IB that creates a circumferential bias field HB . [Copyright &y& Elsevier]

Abstract: We studied the domain wall (DW) propagation of magnetically-bistable Fe–Co-rich microwires paying attention to the effect of applied and internal stresses. Magnetic field, H, dependences of DW velocity, v, were measured in Co41.7Fe36.4Si10.1B11.8 microwires with metallic nucleus diameters (from 13μm to 18μm) and with different ρ-ratio between the metallic nucleus diameter, d, and total microwire diameter, D. DW velocity decreased under the application of stresses. From measured dependences we evaluated DW mobility, S, dependence on the applied stresses. The results obtained for Co41.7Fe36.4Si10.1B11.8 sample show that S decreases with the increasing of applied stresses, σ a . The observed dependences manifest that increasing of magnetoelastic anisotropy results in the decreasing of DW mobility and DW velocity [Copyright &y& Elsevier]

Abstract: The giant magneto-impedance (GMI) attracted growing attention especially owing to the large sensitivity of the electrical impedance to the DC magnetic field, when the relatively high-frequency electrical current flows along the magnetic conductor. Such GMI effect is the highest in soft magnetic wires with vanishing magnetostriction constant. The last strong tendency in miniaturization of the magnetic sensing elements has resulted in the development of the thinner glass-coated wires produced by the Taylor–Ulitovsky method (1–30μm in diameter). Recent significant progress in tailoring of magnetically soft Co-rich glass-coated microwires allows to enhance significantly the GMI ratio (up to about 600%) in compositions with vanishing magnetostriction constant, λ s, at frequencies between 100kHz and 20MHz. In this paper we report novel results on the GMI effect at high-frequency region (between 10MHz and 500MHz) in different families of amorphous microwires (Fe-rich, with positive magnetostriction constant, Co-rich with negative magnetostriction constant and Co–Fe-rich with nearly-zero magnetostriction constant) fabricated by the Taylor–Ulitovsky method. The differences in observed dependencies for these families of compositions have been interpreted in terms of difference in the magnetoelastic anisotropy. [Copyright &y& Elsevier]

Abstract: We studied the velocity of domain wall propagation, v, of Fe69Si10B15C6 with different metallic nucleus diameter, d, and different total diameter, D (d=14μm, D=33μm and d=18μm, D=23.4μm, respectively) in the temperature range between 78 and 300K and at different frequencies of applied magnetic field. It is worth mentioning that v(H) dependence is essentially not linear, showing significantly higher domain wall mobility, S=dv/dH, at lower field limit. Domain wall mobility, S, increases significantly with increase in temperature. From v(H) dependence, the critical field, H cr, associated with the change of the slope on v(H) dependence and critical propagation fields H 01 and H 02 for the lower and higher field regions, respectively, are determined. All characteristics, v(H) dependence, S(H) dependence and H cr are sensitive to the sample geometry, i.e., to the internal stresses. The origin of such dependence on internal stresses is discussed in terms of magnetoelastic energy contribution. [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]

• 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]

The influence of annealing on structure and temperature and magnetic field dependences of resistance of Cu 100-x Co x (x = 5, 10, 20) glass-coated microwires prepared using Taylor-Ulitovsky has been studied. All Cu 100-x Co x microwires present resistivity minimum at certain temperature, T m . This minimum is very well defined for as-cast samples. T m -values decrease after annealing (from about 50 K to about 25 K). Observed R(T) dependences and the minimum are well affected by applied magnetic field. Additionally we observed a significant increasing of the GMR effect in the annealed samples (at 400 °C) with long enough annealing time (up to 34% GMR effect). Considerable enhancement of the GMR effect related with structural changes of the studied samples is promising for technical applications. [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 effect of the annealing on the structure, transport properties and the magnetoresistance of Cu 95 Co 95 glass-coated microwires prepared by Taylor-Ulitovsky technique. We observed a significant enhancement of the magnetoresistance, MR, effect in the samples annealed at 400 °C. On the other hand low temperature annealing (150–200 °C) allowed stress relaxation and elimination of the texture observed in as-prepared samples, although only slightly affects the MR effect. Annealing considerably affects the temperature dependence of resistivity. We observed resistivity minimum in both as-prepared and annealed samples associated with the Kondo effect. This minimum persists even under magnetic field in as-prepared samples. In annealed sample minimum disappears under applied magnetic field. Observed enhancement of the MR effect therefore must be attributed to the structural changes of the studied samples. [ABSTRACT FROM AUTHOR]

Abstract: We studied the domain wall (DW) dynamics of magnetically bistable amorphous glass-coated Fe74B13Si11C2 microwires. In according to our experimental results magnetic field dependences of DW velocity of studied microwires can be divided into two groups: with uniform or uniformly accelerated DW propagation along the microwire. Strong correlation between the type of the magnetic field dependence of domain wall velocity, v(H), and the distribution of the local nucleation fields has been observed. Moreover, we observed abrupt increasing of DW velocity (jump) on the magnetic field dependences of the domain wall velocity, v(H), for the both types of the v(H) dependences. At the same time usual linear increasing of the domain wall velocity with magnetic field persists below these jumps. It was found that the jump height correlates with the location of nucleation place of the new domain wall. We have measured local nucleation field distribution in all the microwires. From local nucleation field distribution we have obtained the DW nucleation locations and estimated the jump height [Copyright &y& Elsevier]

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]