Modeling of Magnetic Field Influence on Electrophysical Effects in Magnetoimpedance Microwires

The pursuance of the research of dependency between magnetoimpedance effect and the distribution of magnetization relatively to amorphous ferromagnetic microwire axis is important for creating highsensitive magnetic field sensors. Distribution of signal in skin-layer is considered as a function of the magnetic properties of the wire material, bias current flowing through it, strength and orientation of the external magnetic field. The impact of these factors on the signal of microwire with circumferential (helical) anisotropy is analyzed on the base of numerical simulation

Effective Impedance Method for In situ Ellipsometry Analysis of Magnetic Films

The method of effective surface impedance is proposed and applied for in situ characterisation of magnetic structures. For any ellipsometry investigations a proper choice of a physical model is important for solving the inverse problem. Reasonable approximations used for in situ ellipsometry monitoring are assumptions of a constant rate of layer growth and stable optical parameters. Standard ellipsometry analysis requires the model response to be calculated from every layer in the structure. Errors from underlying layers propagate through the entire structure and accumulate. In this case a method of a pseudosubstrate is used which approximates the underlying structure as a single interface (so called virtual interface), rather than tracking the entire sample history. The virtual interface is placed at some level and growth is modelled on this interface with no knowledge retained for the underlying structure. There are various methods for describing the virtual interface. In this paper, the concept of the effective impedance is used which requires only three measurement data points and is convenient for combined investigation of optical and magneto-optical properties. The algorithm is based on the calculation of the characteristic matrix of the layer (Abeles matrix) and surface impedance of the virtual interface using two ellipsometric experimental data points. The method is successfully used to analyse Co / SiCo films. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3358

Study of Capacitive and Electrical Conductivity Characteristics of the System «Nanostructured Electrodes - Dielectric Liquid»

The results of research of capacitive and conductive characteristics of the system "the nanostructured metal electrodes – dielectric liquid" are given. It is shown the difference of states near the electrodes of electric double layers on the surfaces of copper and tungsten electrodes. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3636

From the Dynamic Demagnitizing Factor to the Heat Capacity of a Nanodispersed Magnetic Fluid

A technique for the measurement of the dynamic demagnetizing factor, used for the description of magnetic fluid magnetization disturbance caused by a sonic wave has been offered. The formula for the calculation of heat capacity Cp of the synthesized magnetic colloids, which includes the pa-rameter Nd has been obtained. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3365

High Sensitivity Magnetic Sensors Based on Off-diagonal Magnetoimpedance in Amorphous FeCoSiB Wires

The magnetoimpedance (MI) effect has a potential for the development of high performance magnetic sensors. For sensor applications, off-diagonal configuration is preferable when the MI element is excited by ac current and the output is detected from the coil. In the present work, the off-diagonal sensor design was advanced by utilising a complex waveform excitation produced by a microcontroller and applied to a multiple wire MI element. For optimised excitation with a waveform close to a positive half sine form and characteristic frequency of 8 MHz the field resolution of about 60 mV/Oe was achieved. The pulse excitation does not require an additional bias since it includes controllable low frequency components. The concept of microcontroller driven sensor element could be attractive for the development of intellectual sensors. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3358

Influence of Surfactants on the Activity Powders of Barium Hexaferrite, Prepared by Wet Grinding

Study the influence of citric acid and isopropyl alcohol on processes of wet grinding mixture of starting ferrite constituting components and synthesized ferrite charge. Found that the introduction of additives during wet grinding allows to significantly reduce the temperature of synthesis and sintering ferrite raw blanks. Increased activity of powders is explained by the formation of active the gelled layers on the surface of particles in the process of wet grinding

Influence of Surfactants on the Activity Powders of Barium Hexaferrite, Prepared by Wet Grinding

Study the influence of citric acid and isopropyl alcohol on processes of wet grinding mixture of starting ferrite constituting components and synthesized ferrite charge. Found that the introduction of additives during wet grinding allows to significantly reduce the temperature of synthesis and sintering ferrite raw blanks. Increased activity of powders is explained by the formation of active the gelled layers on the surface of particles in the process of wet grinding

LTCC-technology for Producing Hexaferrites

In the review examined the possibility of using LTCC-technology for obtaining hexaferrites as reaction additives glasses Bi2O3-B2O3-SiO2-ZnO (BBSZ) and BaCu (B2O5) (BCB) to reduce the sintering temperature. It is shown that compatibility between hexaferrites with the addition BBSZ, BCB and silver paste, which is a key requirement in the manufacturing process LTCC-components. Considered the possibility of co-sintering of ferrites and dielectric tape composites. It was established that for the realization of defectfree LTCC-composite need to control the shrinkage of the two tapes. In this connection becomes an important concept of zero shrinkage and limiting sintering

On Properties of Magneto-dielectric Composites in the Effective Medium Approximation

The development of ultra-broadband composite absorbers of electromagnetic waves depends largely on optimal combination of the medium characteristics that determine their absorption capacity and conditions for impedance matching and destructive interference. It is possible to achieve a higher absorption level in a wider frequency band by combining a variety of mechanisms enhancing the loss of electromagnetic field energy, for example, by combining specific constituents in a composite matrix. The analysis of various mix-ing models for constituent parameters is carried out in the effective medium approximation for ferrite-dielectric composites. It appears that the standard mixing rules do not explain the increase in the effective permittivity of ferrite composites in comparison with that of bulk ferrites. The proposed mechanism of such increase is based on the conductive properties of the ferrite granules and the equivalent capacitance effect. The developed model of permittivity calculation is based on the equivalent capacitor circuits and gives a satisfactory agreement with the experimental data. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3640

Influence of Mass Transfer Processes on Couette Flow of Magnetic Fluid

This article describes the results of a theoretical study of magnetic fluid two-dimensional Couett flow in magnetic fluid seal model in view of mass transfer processes. It has been shown that very inhomogeneous magnetic field in seal gap lead to magnetic particle concentration rearrangement due to magnetophoresis and Brownian diffusion. In turn, it lead to inhomogeneous magnetic fluid viscosity and change in local and integral shearing force at channel walls. Integral shearing force has been shown to depend on magnetic field and magnetic fluid parameters. Closely-packed fluid density distribution conditions have been defined. Proposed theory covers real magnetic fluid seal performance features adequately. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3360