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

Minkowski-type and Alexandrov-type theorems for polyhedral herissons

Classical H.Minkowski theorems on existence and uniqueness of convex polyhedra with prescribed directions and areas of faces as well as the well-known generalization of H.Minkowski uniqueness theorem due to A.D.Alexandrov are extended to a class of nonconvex polyhedra which are called polyhedral herissons and may be described as polyhedra with injective spherical image.Comment: 19 pages, 8 figures, LaTeX 2.0

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

Impedance of nanometer thickness ferromagnetic Co40Fe40B20 films

Nanocrystalline Co40Fe40B20 films, with film thickness tf = 100 nm, were deposited on glass substrates by the magnetron sputtering method at room temperature. During the film deposition period, a dc magnetic field, h = 40 Oe, was applied to introduce an easy axis for each film sample: one with h||L and the other with h||w, where L and w are the length and width of the film. Ferromagnetic resonance (FMR), ultrahigh frequency impedance (IM), dc electrical resistivity (ρ), and magnetic hysteresis loops (MHL) of these films were studied. From the MHL and r measurements, we obtain saturation magnetization 4πMs = 15.5 kG, anisotropy field Hk = 0.031 kG, and r = 168 mW.cm. From FMR, we can determine the Kittel mode ferromagnetic resonance (FMR-K) frequency fFMRK = 1,963 MHz. In the h||L case, IM spectra show the quasi-Kittel-mode ferromagnetic resonance (QFMR-K) at f0 and the Walker-mode ferromagnetic resonance (FMR-W) at fn, where n = 1, 2, 3, and 4. In the h||w case, IM spectra show QFMR-K at F0 and FMR-W at Fn. We find that f0 and F0 are shifted from fFMRK, respectively, and fn = Fn. The in-plane spin-wave resonances are responsible for those relative shifts

Morphology and microstructure evolution of gold nanostructures in the limited volume porous matrices

The modern development of nanotechnology requires the discovery of simple approaches that ensure the controlled formation of functional nanostructures with a predetermined morphology. One of the simplest approaches is the self-assembly of nanostructures. The widespread implementation of self-assembly is limited by the complexity of controlled processes in a large volume where, due to the temperature, ion concentration, and other thermodynamics factors, local changes in diffusion-limited processes may occur, leading to unexpected nanostructure growth. The easiest ways to control the diffusion-limited processes are spatial limitation and localized growth of nanostructures in a porous matrix. In this paper, we propose to apply the method of controlled self-assembly of gold nanostructures in a limited pore volume of a silicon oxide matrix with submicron pore sizes. A detailed study of achieved gold nanostructures’ morphology, microstructure, and surface composition at different formation stages is carried out to understand the peculiarities of realized nanostructures. Based on the obtained results, a mechanism for the growth of gold nanostructures in a limited volume, which can be used for the controlled formation of nanostructures with a predetermined geometry and composition, has been proposed. The results observed in the present study can be useful for the design of plasmonic-active surfaces for surface-enhanced Raman spectroscopy-based detection of ultra-low concentration of different chemical or biological analytes, where the size of the localized gold nanostructures is comparable with the spot area of the focused laser beam. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.3.1.5.1Ministry of Education and Science of the Russian Federation, Minobrnauka: К-2018-036, N 211Russian Foundation for Fundamental Investigations, RFFI: 19-32-50058European Commission, ECMinistry of Science and Technology, MOSTFunding: This research was funded by H2020-MSCA-RISE2017-778308-SPINMULTIFILM Project, the scientific– technical program, ‘Technology-SG’ [project number 3.1.5.1], Ministry of Education and Science of the Russian Federation in the framework of Increase Competitiveness Program of NUST «MISiS» [№ К-2018-036], implemented by a governmental decree dated 16th of March 2013, N 211 and Russian Foundation for Fundamental Investigations [project number 19-32-50058].Acknowledgments: D.V.Y. greatly acknowledges the World Federation of Scientists National Scholarship Program. E.Yu.K., D.V.Y., V.D.B., and V.S. greatly acknowledge the European Union program Mobility Scheme for Targeted People-to-People-Contacts (MOST) for supporting research visits

Morphology and Microstructure Evolution of Gold Nanostructures in the Limited Volume Porous Matrices

The modern development of nanotechnology requires the discovery of simple approaches that ensure the controlled formation of functional nanostructures with a predetermined morphology. One of the simplest approaches is the self-assembly of nanostructures. The widespread implementation of self-assembly is limited by the complexity of controlled processes in a large volume where, due to the temperature, ion concentration, and other thermodynamics factors, local changes in diffusion-limited processes may occur, leading to unexpected nanostructure growth. The easiest ways to control the diffusion-limited processes are spatial limitation and localized growth of nanostructures in a porous matrix. In this paper, we propose to apply the method of controlled self-assembly of gold nanostructures in a limited pore volume of a silicon oxide matrix with submicron pore sizes. A detailed study of achieved gold nanostructures' morphology, microstructure, and surface composition at different formation stages is carried out to understand the peculiarities of realized nanostructures. Based on the obtained results, a mechanism for the growth of gold nanostructures in a limited volume, which can be used for the controlled formation of nanostructures with a predetermined geometry and composition, has been proposed. The results observed in the present study can be useful for the design of plasmonic-active surfaces for surface-enhanced Raman spectroscopy-based detection of ultra-low concentration of different chemical or biological analytes, where the size of the localized gold nanostructures is comparable with the spot area of the focused laser beam