There is a pressing need for improving of the high-frequency magneto-impedance effect of cost-effective soft magnetic materials for use in high-performance sensing devices. The impact of the ...stress-annealing on magnetic properties and high frequency impedance of Fe-rich glass-coated microwires was studied. Hysteresis loops of Fe-rich microwires have been considerably affected by stress- annealing. In stress-annealed Fe- rich microwire we obtained drastic decreasing of coercivity and change of character of hysteresis loop from rectangular to linear. By controlling stress-annealing conditions (temperature and time) we achieved drastic increasing (by order of magnitude) of giant magnetoimpedance ratio. Coercivity, remanent magnetization, diagonal and of-diagonal magnetoimpedance effect of Fe-rich microwires can be tuned by stress-annealing conditions: annealing temperature and time. Observed experimental results are discussed considering relaxation of internal stresses, compressive "back-stresses" arising after stress annealing and topological short range ordering.
We present an overview of the factors affecting soft magnetic properties and giant magnetoimpedance (GMI) effect as well as of post processing tools allowing optimization of magnetic softness and GMI ...effect of thin amorphous wires. Generally low coercivity and high GMI effect have been observed in as-prepared Co-rich microwires. The magnetoelastic anisotropy is one of the most important parameters that determine the magnetic softness and GMI effect of glass-coated microwires. Annealing at adequate conditions can be very effective for manipulation the magnetic properties of amorphous ferromagnetic glass-coated microwires. After annealing of Co-rich we can observe transformation of inclined hysteresis loops to rectangular and coexistence of fast magnetization switching and GMI effect in the same sample. Using stress-annealing, GMI effect of Co-rich microwires can be increased. We demonstrated that the switching field value of microwires can be tailored by annealing in the range from 4 to 200 A/m. Similarly stress-annealing allows induction of transverse magnetic anisotropy and improvement of magnetic softness and GMI effect in amorphous Fe-rich microwires. On the other hand in Fe-rich FeCuNbSiB microwires after appropriate annealing we observed considerable magnetic softening and GMI effect enhancement.
•Trends in optimization of GMI effect in amorphous and nanocrystalline microwires.•Engineering of magnetic properties and GMI effect in as-prepared amorphous microwires.•Magnetic softening of Fe-rich microwires after stress-annealing.•Improvement of GMI effect after stress-annealing of Fe- and Co-rich microwires.•Improvement of GMI effect after nanocrystallization of Fe- -rich microwires.
► Systematic studies of the optimization of magnetic properties and GMI effect of microwires. ► Systematic study of the effect of magnetoelastic anisotropy on magnetic properties of microwires. ► ...Contextual discussions of the impact of magnetoelastic anisotropy on GMI effect of microwires. ► Systematic study of effect of magnetostatic interactions on magnetic properties of microwires. ►Contextual discussions of magnetic microwires applications for magnetic microsensors.
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.
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.
As-prepared and annealed Heusler-type NiMnGa glass-covered microwires present considerable dependence of magnetization on magnetic field values attributed to the magnetic and atomic disorder. We ...observed that annealing conditions strongly affect structure, temperature dependence of magnetization and Curie temperature of microwires. After annealing a magnetic phase transition is observed at about 270–300 K which is beneficial for magnetic solid state refrigeration. Exchange bias effect, enhanced coercivity values at low temperature and features that can be attributed to coexistence of two magnetic phases are observed after long annealing of NiMnGa glass-covered microwires.
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•Tunability of magnetic properties of Heusler-type microwires by annealing.•Magnetic phase transition near room temperature beneficial for magnetic solid state refrigeration.•An exchange bias of about 20 Oe at 5 K in annealed NiMnGa microwires.•An enhanced coercivity at low temperatures in annealed NiMnGa microwires.
We studied the correlation between magnetic softness and magnetostriction coefficient for as-prepared and annealed Co–Fe-rich microwires. We found that the hysteresis loops and magnetostriction ...coefficients of Co and Fe-rich microwires depend not only on the chemical composition of the metal but also on internal stress. Consequently, both hysteresis loop and magnetostriction coefficient can be adjusted by annealing. We varied the time and temperature of annealing and observed changes of the character of the hysteresis loops. These changes correlated with evolution of the magnetostriction coefficient. Drastic changes of the hysteresis loop for Co-rich microwires were attributed to changes of the sign and value of the magnetostriction coefficient.
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 report on comparison of magnetic properties and GMI effect of as-prepared, annealed and stress-annealed Fe- and Co-rich microwires. Generally after annealing hysteresis loop of Co-rich microwires ...becomes rectangular. Stress annealed Co-rich microwires exhibit lower coercivity as-compared with conventionally annealed samples. Additionally we observed increasing of GMI ratio after stress annealing and its decreasing after conventional annealing. In the case of Fe-rich microwires the hysteresis loops of stress annealed samples present linear shape with low coercivity. Considerable improvement of GMI effect in Fe-rich microwires after stress annealing is observed.
For interpretation of observed changes of hysteresis loops after stress annealing we considered internal stresses relaxation and different mechanisms of stress-induced anisotropy.
Observed versatile properties of stress annealed glass-coated microwires with enhanced and tunable soft magnetic properties make them suitable for technological sensing applications.
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•Extremely low switching field in stress-annealed Co-based microwires.•Magnetic softening of Fe-rich microwires after stress-annealing.•Improvement of GMI effect after stress-annealing of Fe- and Co-rich microwires.
•P addition restricts formation of hetero-amorphous structure in Fe-rich alloys.•P addition stabilize intergranular amorphous matrix during de-vitrification.•The ribbon heterogeneity induced mixed ...anisotropy governs the coercivity (Hc).•4 at% P content show optimal magnetic properties of low Hc and High Ms.
The influence of P on amorphizing ability, as-quenched microstructure, thermo-physical and soft magnetic properties of Fe–rich (i) Fe81B15-xPxSi2Nb1Cu1 (ii) Fe82B14-xPxSi2Nb1Cu1 and (iii) Fe83B13-xPxSi2Nb1Cu1 (x = 0, 2, 4, 6, 8 at%) melt-spun alloys are investigated. The substitution of P improves amorphization of alloys and restricts the formation of hetero-amorphous microstructure for Fe 83 at% ribbons at around (x = 8). The improvement in short range ordering of P containing clusters with varying Fe content has been discussed within the framework of Cluster-Glue atom model and supported by experimental thermal parameters. The optimal P content in Fe-rich alloys in the range of 4 ≤ x ≤ 6 delivered favourable thermal properties of high primary and secondary crystallization onset temperature viz; Tx1, Tx2 and temperature span ΔT between these onsets. The P substitution drastically restricts the precipitation of secondary crystallites with reduced enthalpy of secondary crystallisation (ΔH2) during annealing and favourably assists in attaining maximum magnetic moment during the primary crystallization stage. Moreover, the P substitution (4–8 at%) effects refinement of α-Fe nanocrystallites and promotes low coercivity (Hc < 20 A/m) in nanocomposite alloys. On contrary, the P substitution linearly reduces saturation magnetization (Ms) by weakening ferromagnetic exchange coupling and ferromagnetic dilution. An optimal content of 4 at% P offers favourable combination of low Hc and High Ms in both amorphous and nanocomposite state.
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.
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