Off-diagonal impedance in amorphous wires and application to linear magnetic sensors

The magnetic-field behaviour of the off-diagonal impedance in Co-based amorphous wires is investigated under the condition of sinusoidal (50 MHz) and pulsed (5 ns rising time) current excitations. For comparison, the field characteristics of the diagonal impedance are measured as well. In general, when an alternating current is applied to a magnetic wire the voltage signal is generated not only across the wire but also in the coil mounted on it. These voltages are related with the diagonal and off-diagonal impedances, respectively. It is demonstrated that these impedances have a different behaviour as a function of axial magnetic field: the former is symmetrical and the latter is antisymmetrical with a near linear portion within a certain field interval. In the case of the off-diagonal response, the dc bias current eliminating circular domains is necessary. The pulsed excitation that combines both high and low frequency harmonics produces the off-diagonal voltage response without additional bias current or field. This suits ideal for a practical sensor circuit design. The principles of operation of a linear magnetic sensor based on C-MOS transistor circuit are discussed.Comment: Accepted to IEEE Trans. Magn. (2004

Ferromagnetic Wires Composite Media with Tunable Scattering Spectra at Microwaves

We demonstrate composite media with ferromagnetic wires that exhibit a frequency region at the microwave regime with scattering spectra strongly dependent on an external magnetic field or stress. These tunable composite materials have recently been proposed theoretically; however, no direct experimental verification has been reported. We used composite materials with predominantly oriented CoFeCrSiB glass-coated amorphous wires having large magnetoimpedance at GHz frequencies. The free space measurements of reflection and transmission coefficients were conducted in the frequency range 1-8 GHz in the presence of an external static magnetic field or stress applied to the whole sample. In general, the transmission spectra show greater changes in the range of 10dB for a relatively small magnetic field of few Oe or stress of 0.1 MPa. The obtained results are quantitatively consistent with the analytical expressions predicted by the effective medium arguments. The incident electromagnetic wave induces an electrical dipole moment in each wire, the aggregate of which forms the effective dipole response of the whole composite structure in the radiative near or far field region. The field and stress dependences of the effective response arise from a field or tensile stress sensitivity of the ac surface impedance of a ferromagnetic wire. In the vicinity of the antenna resonance the variations in the magneto-impedance of the wire inclusions result in large changes of the total effective response. A number of applications of proposed materials is discussed including the field tunable microwave surfaces and the self-sensing media for the remote non-destructive evaluation of structural materials

Stress effect on magnetoimpedance (MI) in amorphous wires at GHz frequencies and application to stress-tunable microwave composite materials

The effect of tensile stress on magnetoimpedance (MI) in CoMnSiB amorphous wires at microwave frequencies (0.5-3 GHz) is investigated both experimentally and theoretically. In the presence of the dc bias magnetic field of the order of the anisotropy field, the impedance shows very large and sensitive change when the wire is subjected to a tensile stress: 100% and 60% per 180 MPa for frequencies 500 MHz and 2.5 GHz, respectively. It is demonstrated that this behavior owes mainly to the directional change in the equilibrium magnetization caused by the applied stress and field, which agrees well with the theoretical results for the surface impedance. This stress effect on MI is proposed to use for creating microwave stress-tunable composite materials containing short magnetic wires. The analysis of the dielectric response from such materials shows that depending on the stress level in the material, the dispersion of the effective permittivity can be of a resonant or relaxation type with a considerable change in its values (up to 100% at 600 MPa). This media can be used for structural stress monitoring by microwave contrast imaging

Left-handed metacomposites containing carbon fibers and ferromagnetic microwires

We investigate the microwave behavior of polymer-based metacomposites containing ferromagnetic microwires and carbon fibers. A notable transmission window is observed from the metacomposite containing 3mm spaced parallel microwire array in 1-7 GHz, verifying a left-handed behavior. In the hybrid metacomposites containing both parallel wires and carbon fibers, such transmission window is preserved with a much higher transmittance due to the improved impedance match and hence decreased reflection loss. The introducing of continuous carbon fibers leads to a remarkable anisotropic behavior: left-handed properties are turned on/off by rotating the electric excitation by 90 degrees. The proposed metacomposites are promising for microwave cloaking and sensing applications for aerospace-graded structural components

Optomagnetic composite medium with conducting nanoelements

A new type of metal-dielectric composites has been proposed that is characterised by a resonance-like behaviour of the effective permeability in the infrared and visible spectral ranges. This material can be referred to as optomagnetic medium. The analytical formalism developed is based on solving the scattering problem for considered inclusions with impedance boundary condition, which yields the current and charge distributions within the inclusions. The presence of the effective magnetic permeability and its resonant properties lead to novel optical effects and open new possible applications.Comment: 48 pages, 13 figures. accepted to Phys. Rev. B; to appear vol. 66, 200

Вплив похідних тіазолідину на варіабельність серцевого ритму і показники крові експериментальних тварин за умов гіпобаричної гіпоксії

Heart rate variability (HRV ) parameters and hematological indices in rats under hypobaric hypoxia duringtreatment by a thiazolidine derivative substance Les-589 (potassium salt of 3-(5-phenylpropeniliden rhodamine-3-yl)-propanoic acid) were studied. Hypobaric hypoxia was developed in altitude chamber for 1 hour under conditionsidentical height of 6000 m above sea level, 45 minutes after injection of Les-589. Thiotriazolin was applied as areference drug.After one day after exposure to hypoxia, according to blood parameters and hematological indices, adaptiveresponse develops by the type of insufficient adaptation. The effect of the prior administration of Les-589, similar tothe effect of a reference drug Thiotriazolin, in the time of post-hypoxic period developed reactions of an increasedactivation, which indicates a favorable course of adaptation.Considering the parameters of HRV was found that prior administration of Les-589 within studied terms of posthypoxicperiod leads to earlier and more effective recovery of various links of regulatory systems, compared withhypoxia. This is consistent with an estimated type of adaptation processes, based on hematological parametersand indices.Исследовали параметры вариабельности сердечного ритма, а также гематологические показатели и индексы у крыс при гипобарической гипоксии на фоне применения производной тиазолидина – вещества Les-589 (калийная соль 3-(5-фенилпропенилиденроданин-3-ил)-пропионовой кислоты). Гипобарическую гипоксию моделировали в барокамере в течение 1 ч в условиях, идентичных высоте 6000 м над уровнем  моря, через 45 мин после введения Les-589. Как эталонный препарат использовали тиотриазолин.Через сутки после влияния гипоксии, судя по показателям крови и гематологическим индексам, приспособительная реакция развивается по типу неполноценной адаптации. В отличие от этого, эффект предварительного введения Les-589, аналогично эффекту тиотриазолина как эталонного препарата, в этот срок постгипоксического периода реализуется реакцией повышенной активации, что свидетельствует о благоприятном развитии адаптации.На основании параметров вариабельности сердечного ритма установлено, что предварительное  введение Les-589 в исследуемые сроки постгипоксического периода приводит к более быстрому и эффективному восстановлению уровня различных звеньев регуляторных систем по сравнению с гипоксией. Это соответствует определенному на основании гематологических показателей и индексов типу развития адаптационных процессовДосліджували параметри варіабельності серцевого ритму, а також гематологічні показники та індекси в щурів при гіпобаричній гіпоксії на фоні застосування похідної тіазолідину – речовини Les-589 (калійна сіль3-(5-фенілпропеніліденродамін-3-іл)-пропанової кислоти). Гіпобаричну гіпоксію моделювали у барокамері впродовж 1 год за умов, ідентичних висоті 6000 м над рівнем моря, через 45 хв після введення Les-589. Якеталонний препарат використовували тіотріазолін. Через добу після впливу гіпоксії, з огляду на показники крові та гематологічні індекси, пристосуваль-на реакція розвивається за типом неповноцінної адаптації. Натомість ефект попереднього введення Les-589, аналогічно до ефекту тіотріазоліну як еталонного препарату, в цей термін постгіпоксичного періоду реалізується реакцією підвищеної активації, що свідчить про сприятливий перебіг адаптації. На основі параметрів варіабельності серцевого ритму встановлено, що попереднє введення Les-589 у досліджувані терміни постгіпоксичного періоду призводить до швидшого й ефективнішого відновлення рівня різних ланок регуляторних систем порівняно з гіпоксією. Це узгоджується з визначеним на основі гематологічних показників та індексів типом розвитку адаптаційних процесів