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ABSTRACT: The magnetoimpedance (MI) response of near-zero magnetostriction Co-based amorphous ribbons with different width ranging from 0.35 mm to 0.90 mm was investigated in the frequency range of 10 MHz–3.5 GHz. It was found that the wider ribbon displays the softer magnetic behavior and larger magnetoimpedance. MI response is characterized by two symmetrical peaks corresponding at the two opposite directions of applied magnetic field. The value of magnetic field at the peaks of MI should be assigned to the anisotropy field. Frequency dependencies of anisotropy field for the range 500–1000 MHz could be understood in the framework of skin penetration effect in the ribbons except to that of lowest width (0.35 mm) where the ferromagnetic resonance phenomenon could be predominant at this frequency range. Ferromagnetic resonance was detected in all samples, and for magnetic fields above 4 kA/m the square of resonance frequency quadratically fits vs. the applied field. Given the saturation magnetization, both the anisotropy field and the Landé factor have been determined.
Journal of Applied Physics. 02/2013; 113(5):053905.
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ABSTRACT: We report on studies of domain wall propagation of magnetically-bistable Fe-Co-rich microwires paying attention on the effect of applied and internal stresses. We measured magnetic domain propagation in various magnetic Fe-Co-rich amorphous microwires with metallic nucleus diameters (from 2.8 microm to 18 microm) using Sixtus Tonks-like experiments. We found that application of applied stresses and increasing of internal stresses result in decreasing of domain wall (DW) velocity. We assume that in order to achieve higher DW propagation velocity at the same magnetic field and enhanced DW mobility, special attention should be paid to the decrease of magnetoelastic energy.
Journal of Nanoscience and Nanotechnology 09/2012; 12(9):7582-6. · 1.56 Impact Factor
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ABSTRACT: 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
N
, determined by the microwires inhomogeneities, an almost linear DW velocity,v, dependence on magnetic field, H, is found. Quite fast DW propagation (vtill 3000m/s atH about 65A/m) has been observed. When the applied magnetic field exceeds H
N
, 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.
KeywordsMicrowire–Glass-covered microwire–Domain wall propagation
Journal of Superconductivity and Novel Magnetism 05/2012; 24(1):851-854. · 0.65 Impact Factor
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ABSTRACT: 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 Co67Fe3.9Ni1.5B11.5Si14.5M0.6 and Fe74B13Si11C2 amorphous microwires. Fe74B13Si11C2 microwires have rectangular hysteresis loop, while Co67Fe3.9Ni1.5B11.5Si14.5M0.6 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.
KeywordsMicrowire–Glass-covered microwire–Magnetostatic coupling–Stray fields
Journal of Superconductivity and Novel Magnetism 04/2012; 24(1):541-547. · 0.65 Impact Factor
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ABSTRACT: 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.
Applied Physics A 04/2012; 103(3):653-657. · 1.63 Impact Factor
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ABSTRACT: 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 0.9–17GHz.
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.
Applied Physics A 04/2012; 103(3):693-697. · 1.63 Impact Factor
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ABSTRACT: Memory effects in Heisenberg spin glasses: Spontaneous restoration of the original spin configuration rather than preservation in a frozen state J. Appl. Phys. 111, 07E147 (2012) First order reversal curve studies of permanent magnets J. Appl. Phys. 111, 07A728 (2012) High speed magnetisation reversal in heat-assisted magnetic recording In this paper we present the calculated spectra of signals originating from the magnetization reversal of a system of two identical bistable magnetic moments. We show that in contrast to the spectrum characteristic of magnetization reversal in any common ferromagnetic material, the amplitude of the harmonics in the calculated spectra can change periodically. Also, we present experimental spectra of signals induced by the magnetization reversal of two magnetically coupled glass-covered. Periodic variation of the harmonics amplitude predicted by the calculations was observed in the experimental spectra. V C 2012 American Institute of Physics. [doi:
Journal of Applied Physics 01/2012; 111(111-07E735):7-735. · 2.17 Impact Factor
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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 (C) 2011 Elsevier B.V. All rights reserved.
Physica B Condensed Matter 01/2012; 407(9):1446-1449. · 1.06 Impact Factor
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Sensors and Actuators A Physical 01/2012; · 1.80 Impact Factor
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ABSTRACT: Smart composites with short-cut Co<sub>68.7</sub>Fe<sub>4</sub>Ni<sub>1</sub>B<sub>13</sub>Si<sub>11</sub>Mo<sub>2.3</sub> 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<sup>-2</sup> to 0.24 cm<sup>-2</sup> , 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.
IEEE Transactions on Magnetics 11/2011; · 1.36 Impact Factor
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ABSTRACT: In this paper, we experimentally studied the effect of applied and residual stresses on the domain-wall (DW) velocity in amorphous Fe-Co-based microwires. We found that application of applied stresses and an increase of internal stresses result in decrease of DW velocity. We assume that in order to achieve higher DW propagation velocity at the same magnetic field and enhanced DW mobility, especial attention should be paid to decrease of magnetoelastic energy.
IEEE Transactions on Magnetics 11/2011; · 1.36 Impact Factor
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ABSTRACT: Thin amorphous magnetically soft microwires attract recently great attention because of their excellent soft magnetic properties and giant magneto-impedance (GMI) effect, thin dimensions and possibility for applications in magnetic micro-sensors. We overview research in the field of development of microwires with high GMI effect and improved features and report novel results on studies of GMI (diagonal and off-diagonal components) at high frequencies (between 10 MHz and 4 GHz) and its correlation with soft magnetic behaviour of thin amorphous microwires (Co-Fe-rich with nearly-zero magnetostriction constant) with metallic diameter between 3 and 20 μm and on optimization of GMI effect. We studied and analyzed low-field hysteresis of GMI effect and its dependence on circular magnetic field and discuss the nature the low-field hysteresis in terms of helical magnetic anisotropy and the effect of the bias field. Choosing samples composition, annealing conditions and geometry we were able to tailor their magnetoelastic anisotropy and respectively magnetic softness and GMI.
Journal of Physics Conference Series 07/2011; 303(1):012085.
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ABSTRACT: The correlation between surface domain structure (SDS) and high frequency magneto-impedance (MI) in amorphous microwires has been systematically studied. First, we applied the magneto-optical polarizing microscopy to determine the SDS and found that it is considerably different in unstressed microwire and in microwires to which tensile and torsional stress were applied. Then, we measured the longitudinal and off-diagonal MI in these microwires and also observed quite different MI dependencies. We analyzed the experimental MI curves and their dependence on the SDS with the help of a simple model that nevertheless yields good qualitative agreement with experiment. We have demonstrated that the analysis of the MI dependencies, especially the off-diagonal one, can reveal the SDS in the microwires. The obtained results can also be useful for magnetic and stress sensing applications.
Journal of Applied Physics 06/2011; 109(11):113924-113924-6. · 2.17 Impact Factor
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ABSTRACT: 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 Co 66 Fe 3.5 B 16 Si 11 Cr 3.5 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.
Journal of Applied Physics 04/2011; · 2.17 Impact Factor
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ABSTRACT: 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.
Journal of Applied Physics 03/2011; 109(7):07A310-07A310-3. · 2.17 Impact Factor
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ABSTRACT: 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 different external stimuli. We have demonstrated the effect of the external magnetic field on microwave response from composites containing CoFeSiBCr amorphous wires in free space at microwave frequency.
MRS Proceedings. 12/2010; 1312.
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ABSTRACT: 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.
Applied Physics Letters 12/2010; 97(25):252507-252507-3. · 3.84 Impact Factor
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ABSTRACT: We have investigated the influence of annealing on the local nucleation fields distribution in amorphous magnetically bistable microwires. The measurements have quite surprisingly shown a considerable increase of the local nucleation fields after annealing of the wire, although it is generally expected that thermal annealing without a magnetic field relieves the internal stresses, which results in a reduction of the nucleation fields. The increase of the local nucleation fields is explained by the disappearance of local inhomogeneities after annealing.
Physica Status Solidi (A) Applications and Materials 11/2010; 208(3):549 - 552. · 1.46 Impact Factor
