This paper describes realization of complex permeability determination for ferrite materials using short coaxial sample holder and vector network analyzer E5071B in frequency range between 300 kHz and 1 GHz. The design of coaxial high frequency sample holder is presented, the principle of measurement and calibration is shown. The extracting of complex permeability from S-parameters is managed based on accomplished formulas, user-friendly program for computer control has been written, and obtained results are explained in detail. In order to verify proposed method, the results of the measurement of NiZn ferrite samples, manufactured by MMG NeoSid, are compared with catalog characteristics.
Current integrator systems usually use active RC integrator circuits. Crucial dificulty associated with this analogue system is the integrator drift. The following paper presents the idea of the active integrator circuit based on inductive and resistive components. This concept allows to eliminate the time drift of the circuit, which is undesired phenomenon resulting from capacitive components working in the traditional negative feedback loop. The SPICE simulations were performed to validate the presented idea. Then, prototype circuit with discrete components was tested. Inductors were based on nanocrystalline and air cores. The developed solution was tested as magnetoelastic sensors transducer, to confirm the ability for long-term, continuous, drift-free, integrator circuit operation. The results were compared with traditional, RC circuit with automatic drift compensation.
Soft magnetic composites (SMCs), which are used in electromagnetic applications, can be described as ferromagnetic powder particles surrounded by an electrical insulating film. These composite materials offer several advantages over traditional laminated steel cores such as reduction in weight and size. They have some unique properties, including three-dimensional isotropic ferromagnetic behaviour, very low eddy current loss, relatively low total core loss at medium and high frequencies, high electrical resistivity and good relative magnetic permeability. FeSi powder was used as a base ferromagnetic material for preparation of soft magnetic composites. The commercial FeSi particles of a precise spherical shape were prepared in two granulometric fractions (up to 150 μm or up to 356 μm). The phenol-formaldehyde resin modified by SiO_{2} nanoparticles was used as an electroinsulating layer. The FeSi particles covered by the synthesized resin were compacted at 800 MPa into the ring samples for magnetic measurements. The final samples were treated thermally under the curing schedule, which was suggested according to thermal degradation of the modified resin.
Current trends in modernization and miniaturization of ferroprobe sensors lead to replacement of amorphous ribbon cores with magnetic microwires. The miniaturization often causes degradation in the parameters of sensors, so, considering measurement of weak magnetic fields, it is necessary to explore noise parameters, temperature drift and stability of the magnetometer output value. The article deals with analysis of microwire sensor noise characteristics based on the experimental data processing. Using one second periodograms, the linear spectral density was processed. Obtained data are compared with corresponding parameters of a relax-type ferroprobe magnetometer.
The article deals with the method of the inherent noise estimation in each channel of a four channel relax-type magnetometer in general laboratory conditions. The day-long development of ambient magnetic field has been recorded and then the data were processed by correlation methods to separate inherent noises of the channels from ambient noise in the statistically best times. The method is applicable for noise estimation of any multi-channel sensoric system and also for the separation of deterministic and stochastic components of signals.
In this work, two soft magnetic Fe_{73}Cu_{1}Nb_{3}Si_{16}B_{7} powder core samples were investigated. Samples were prepared by milling of amorphous Fe_{73}Cu_{1}Nb_{3}Si_{16}B_{7} ribbon at different temperature conditions: sample R, by milling at room temperature and sample L, by cryomilling at temperature of liquid nitrogen. Influence of applied exciting AC magnetic field with various amplitudes on the complex permeability spectra was studied. Obtained results are explained by the dynamics and relaxation phenomenon of domain walls under the influence of AC magnetic field.
Soft magnetic composites represent a remarkable kind of materials with wide variety of use. Magnetic properties are dependent on the materials composition and also on the method of preparation. Ni-Fe-Mo alloys (supermalloy) have high complex permeability and low eddy current losses. Soft magnetic NiZnFe₂O₄ ferrites have low coercivity and intermediate saturation magnetization. The Ni_{80}Fe_{14.7}Mo_{4.5}Mn_{0.5}Si_{0.3} (wt%) powder sample was prepared by mechanical alloying of the chemical elements for 24 h. Ni_{0.3}Zn_{0.7}Fe₂O₄ ferrite is commercially available by Sigma Aldrich. Both powders were mixed at selected ratio and uniaxially compacted at 800 MPa. In this paper, we report the experimental observations of the effects of Ni_{0.3}Zn_{0.7}Fe₂O₄ content on the electromagnetic properties of NiFeMoMnSi/Ni_{0.3}Zn_{0.7}Fe₂O₄. The samples contained 5, 10, and 15% of Ni_{0.3}Zn_{0.7}Fe₂O₄ ferrite and were sintered for 30 min at 800°C. An addition of Ni_{0.3}Zn_{0.7}Fe₂O₄ ferrite caused decrease of complex permeability and increase coercivity of the samples. The 5% of Ni_{0.3}Zn_{0.7}Fe₂O₄ sample exhibits the highest value of the real part of complex permeability (48 at 1 kHz). The 10% of Ni_{0.3}Zn_{0.7}Fe₂O₄ sample showed the lowest total magnetic losses.
The following paper presents original results of study on the magnetoelastic properties of Ni-Zn (nickel-zinc) ferrite material under low magnetizing fields, corresponding to the so-called Rayleigh region. The investigated Ni_{0.36}Zn_{0.64}Fe₂O₄ material was formed into frame-shape sample allowing to obtain uniform stress distribution. Special digitally controlled measurement system was utilized to perform investigation. Obtained results are presented in the paper. On the basis of them mathematical description of magnetoelastic effect in investigated material was developed as an extend of the Rayleigh model of magnetic hysteresis. Comparison of the experimental and modeling results indicates that the developed model is correct.
In the paper the results of investigation on tensile stresses dependence of magnetoelastic characteristics of cores made of 13CrMo4-5 constructional steel are presented. In the investigation step-cooling test treated samples were used. The step-cooling test process is a type of heat treatment simulating effects of passing time and environmental conditions (temperature and stress) on the sample. In the paper the method of testing the influence of stresses on the magnetic characteristics is presented. Frame shaped samples ensured a closed magnetic circuit and homogeneous distribution of stress. It was found that step-cooling test does not significantly influence the magnetoelastic characteristics and the structure of the samples. On the other hand, then tensile stresses significantly change the magnetic characteristics of 13CrMo4-5 constructional steel. That confirms the possibility of using measurements based on the magnetoelastic effect in the stress assessment for industrial non destructing testing of steel constructions.
In this paper we study the influence of the roughness of the copper substrate on the magnetic properties of the FeNi film we electroplate onto it. The roughness and the thickness of the copper substrate are reduced by electropolishing in orthophosphoric acid: we show how to select the working point, which gives the highest smoothness, avoiding defects due to gas evolution. Finally we show how a smoother substrate contributes to reducing the coercivity of the magnetic film grown on it.
The effect of demagnetizing factor and manufacturing procedure on noise of the fluxgate probes, manufactured from metallic glasses, is presented. The fluxgate probes were either tape-wound, or flat, wet-etched ringcore and race-track geometries. When combining low demagnetizing factor and high enough cross-section of the probe, a minimum in the noise dependence can be found. For 50 mm ringcores, in such minimum the noise value as low as 7 pT_{RMS} in 0.1-10 Hz frequency band was achieved, which is very low for an as-cast tape, and has not been reported before.
The paper has been intended to introduce a complex research problem, that is present in aviation, power engineering, mining and transport, with regard to assurance of operational safety for ageing technology, which is exposed to different form of material degradation. Theoretical reasons of non-destructive evaluation (NDE), structural health monitoring (SHM) and active control of material fatigue have been outlined. The magnetic and electromagnetic methods of NDE and SHM such as metal magnetic memory, low frequency eddy current spectroscopy, Barkhausen noise and 3MA have also been presented. The topic has been illustrated by means of practical examples.
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