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We report on specific heat and magnetic properties of thin Gd sheets obtained by means of a cold rolling technique. At temperatures well below Curie temperature TC, the cold rolling has a minor impact on the specific heat CP. However, a well defined k-type anomaly of CP seen in the vicinity of TC in a polycrystalline Gd sample is markedly suppressed in the severely deformed samples. Depression of the λ peak is due to a large decrease of magnetization that presumably originates in a local magnetic anisotropy induced by the severe plastic deformation. Results of calculation of magnetocaloric effect from the CP and magnetization data indicate that the magnetocaloric effect gradually decreases as the degree of plastic deformation increases. This trend is further confirmed by the direct measurements of the adiabatic temperature change ΔTad. [ABSTRACT FROM AUTHOR]

Properly annealed Ni-Mn-Ga glass-covered microwires exhibit a hysteretic anomaly on the temperature dependence of magnetization attributed to the first order martensitic transformation. The temperatures of the structural and magnetic transitions are drastically affected by annealing conditions. Annealed glass-coated Ni-Mn-Ga microwires show a Curie temperature shift close to room temperature. The temperature and magnetic field dependences of magnetization are discussed in terms of atomic disorder, the release of internal stresses, and recrystallization after annealing. [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]

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

We 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]

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

We 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]

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

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