Processing by Joule-heating the Co67Fe3.9Ni1.5B11.5Si14.5Mo1.6 glass-coated microwire allows considerable improvement of magnetic softness and giant magnetoimpedance (GMI) effect. At optimal joule ...heating conditions we observed GMI ratio up to 650%. Observed magnetic softening and GMI ratio improvement have been discussed considering magnetic anisotropy induced by Oersted magnetic field during current annealing, internal stresses relaxation and radial distribution of magnetic anisotropy. The analysis of the GMI ratio 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.
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•Remarkable mprovement of GMI effect in Co -rich microwires current-annealing.•Considerable enhancement of magnetic softness in current-annealed Co-rich microwires.•Interpretation of current annealing effect considering internal stresses relaxation and induced anisotropy.•Evaluation of magnetic field dependence of skin depth in as-prepared and current-annealed microwires.
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.
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•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.
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.
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.
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•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.
In this paper we provide results on effect of post-processing on magnetic properties (giant magnetoimpedance, GMI, effect and domain wall dynamics) 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 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.
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•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.
Processing by stress-annealing (450 MPa, 300 °C, 1 h) the glass-coated microwire of Fe75B9Si12C4 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 Fe75B9Si12C4 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 Fe75B9Si12C4 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.
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•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.
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.
•Stress-annealing induces length distribution of helical magnetic structure in microwire.•Reason of helical length distribution is distribution of magnetic anisotropy.•Length distribution of ...helicality of magnetic structure in microwire is controlled by torsion stress.
We report the stress-annealing induced distribution of the helical magnetic structure in the magnetic microwires. The longitudinal space distribution of the magnetic anisotropy originated by stress-annealing at variable annealing temperature is the reason of the observed effect. We have found that the helicality of magnetic structure in different points of the microwire could be controlled by the external mechanical torsion stress.
•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.
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The effect of Joule-heating on hysteresis loops and giant magnetoimpedance effect, GMI; of Co69.2Fe3.6Ni1B12.5Si11Mo1.5C1.2 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.
•Influence of annealing conditions on hysteresis loops of Co- and Fe-rich microwires.•Coexistence of GMI effect and single domain wall propagation in stress-annealed Co-rich microwire.•Improvement of ...GMI effect in stress-annealed Fe-rich microwires.•High GMI effect in Co-rich microwires with rectangular hysteresis loops.
We provide an overview of the routes allowing the optimization of magnetic softness, giant magnetoimpedance (GMI) effect and domain wall dynamics in one of the families of magnetic microwires: glass –coated microwires prepared using Taylor-Ulitovsky method. The magnetic properties of as-prepared microwires are determined mostly by the magnetoelastic anisotropy. Conventional annealing allows a considerable improvement of the domain wall dynamics in Fe-rich microwires and a slight decrease of the coercivity, however, remarkable magnetic hardening is observed after conventional furnace annealing of Co-rich microwires. Stress annealing of Fe-rich microwires allows a considerable magnetic softening and GMI effect enhancement and even more remarkable improvement of the domain wall dynamics. In Co-rich microwires stress-annealing allows the improvement of GMI effect and even the induction of transverse magnetic anisotropy at high enough annealing temperature. However, the highest GMI effect is observed for stress-annealed Co-rich microwires which present rectangular hysteresis loops. Consequently, annealed Co-rich microwires can present both, fast domain wall propagation and GMI effect.
Observed induced anisotropy and related changes of the magnetic properties are discussed considering the internal stresses relaxation, “back-stresses” and circumferential magnetic field during proposed post-processing.
Consequently, correctly designed post-processing enabled us to design the magnetic anisotropy distribution beneficial for the optimization of the GMI effect and the domain wall dynamics in magnetic microwires.
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