Papers by Keyword: Magnetoimpedance

Abstract: The influence of bias current on the second harmonic in the nonlinear magnetoimpedance in an amorphous microwire with a helical anisotropy is studied theoretically. The voltage response of the microwire is found in the framework of a rotational model. It is shown that the application of the bias current leads to the asymmetry in the field dependence of second harmonic. The second harmonic amplitude is analyzed as a function of the external field, current amplitude and the value of the bias current. The conditions of maximum field sensitivity of the second harmonic are found.

Abstract: We report the giant magnetoimpedance effect in a ferromagnetic metal/insulator/semiconductor (MIS) diode with the Schottky barrier based on the Fe/SiO₂/n-Si structure. It was established that the applied magnetic field strongly influences the impedance of the structure in the temperature range 10—30 K. In this range, there is the pronounced peak in the temperature dependence of the real part of the impedance at frequencies from 10 Hz to 1 MHz. The effect of the magnetic field manifests itself as a shift of the peak of the real part of the impedance. Under the action of a bias voltage of 5 V, the peak of the real part of the impedance similarly shifts toward lower temperatures with and without applied magnetic field.

Abstract: Magnetic properties and magnetoimpedance of [FeNi/Cu]_n/FeNi/Cu (500 nm)/[FeNi/Cu]_m/FeNi MI asymmetric and symmetric structures were studied for multilayeres with different thickness (25, 50 or 170 nm) of permalloy layers. The asymmetric structures in the case of FeNi layers of 50 nm show higher sensitivities comparing with symmetric structures. Asymmetric multilayered structures with 25 nm thick FeNi layers are an interesting subject for further investigation as the interactions between FeNi layers seem to be providing the best MI response.

Abstract: Magnetic properties and magnetoimpedance were studied for as-cast Fe₅Co₇₅Si₄B₁₆ rapidly quenched amorphous ribbons and Fe₅Co₇₅Si₄B₁₆/polymer amorphous ribbon based composites with the following polymer coverings: modified rubber solution in o-xylene, copolymer solution of butyl methacrylate and methacrylic acid in isopropanol and solution of polymethylphenyl resin in toluene. All selected composites showed very good adhesion of the coverings and allowed us to provide long term temperature measurements, including measurements under stress. Polymer coverings have an effect on the temperature sensitivity of the impedance value. The present study demonstrates the promising future for the development of magnetically active conductor/polymer composites for creating new sensors. Modification of the composition and thickness of the polymer coverings can be the basis for creation of the detectors with a unique set of functional properties. Polymer covering can perform the protective and reinforcing role that is particularly important in the case of nanocrystalline alloys and the polymer covering can also affect and improve the functional properties of the magnetic core.

Abstract: Ni₈₀Fe₂₀/Cu composite wires were produced under torsion using electrodeposition method. The total length of the magnetic film deposited onto 50 µm Cu wire is 3 cm and the thickness of the magnetic layer is about 10 µm. All samples showed single peak in magnetoimpedance (MI) curves. The magnitude (ΔZ/Z) % are 260%, 235% and 119% for samples produced under 22.4, 44.8, 89.7 rad/m torsion values, respectively at driving frequency of 160 kHz. MI effect magnitude decreases with increasing applied torsion during the electrodeposition process. A linear change in the second harmonics of output voltage from wire ends as a function of applied magnetic field (coil-less fluxgate effect) was observed in all sample. The sensitivity of coil-less output increases with increasing torsion and maximum sensitivity was observed in the sample produced at 89.7 rad/m torsion.

Abstract: The role of the geometrical parameters was studied for thin film based [FeNi (100 nm)/Cu (3 nm)]₄/FeNi (100 nm)/Cu (500 nm)/[FeNi (100 nm)/Cu (3 nm)]₄/FeNi (100 nm) magnetoimpedance elements with open magnetic flux prepared by lithography technique. The maximum magnetoimpedance sensitivity of 17 %/Oe was obtained for meander shaped sample, exceeding the value of the maximum sensitivity of 5 %/Oe of the single stripe sample. The highest values of the magnetoimpedance were observed for relatively low frequency of order of 50 MHz convenient for technological applications. Both developed technology and obtained results can be useful for optimization of the design of miniaturized detectors of small magnetic field.

Abstract: Magnetic properties and giant magnetoimpedance (GMI) of CuBe/Fe₂₀Co₆Ni₇₄ electroplated wires was studied for frequency of 1 MHz and the amplitude of the driving current of 20 mA with focus on the development of magnetic field detectors of particular types. The possibility of quantitative ferrofluid concentration measurements was demonstrated. GMI of electroplated wire can be useful for the study of the dynamic properties of the ferrofluid. GMI of the electroplated wires in the non-uniform field created by the permanent magnet was studied in the configuration adapted for automatic control lines, machinery control, and positioning systems.

Abstract: A model to describe the influence of longitudinal alternating magnetic field on the nonli-near magnetoimpedance in amorphous wires is proposed. The appearance of even harmonics in the voltage response is shown to arise from the asymmetry in the magnetization reversal process in the wire due to the presence of the longitudinal alternating field. The behavior of even harmonics is analyzed as a function of the external field, alternating field amplitude and current amplitude.

Abstract: The magnetoimpedance (MI) in thin films and magnetic multilayers has been extensively studied in recent years. One of the important problems which is still under discussion is the temperature dependence of MI of the multilayered nanostructures for temperatures up to 200 oC. In this work magnetic properties and temperature dependence of the magnetoimpedance of Fe19Ni81/Cu/Fe19Ni81 multilayers with opened and closed magnetic pathes were studied and comparatively analyzed for the functional temperature interval of + 23 oC to + 160 oC.

Abstract: In this work magnetoimpedance (MI) behaviour was studied experimentally for Fe19Ni81(175 nm)/Cu(350 nm)/Fe19Ni81(175 nm) sensitive elements deposited by rf-sputtering. A constant magnetic field was applied in plane of the sandwiches during deposition perpendicular to the Cu-lead in order to induce a magnetic anisotropy. Sandwiches with different width (w) of FeNi parts were obtained. The complex impedance was measured as a function of the external magnetic field for a frequency range of 1 MHz to 700 MHz for MI elements with different geometries. Some of MI experimental data are comparatively analysed with finite elements numerical calculations data. The obtained results can be useful for optimization of the design of miniaturized MI detectors.