The manufacture and study of the properties of magnetic materials requires the development of new automated devices for measuring their magnetic properties. To obtain nanosized materials with a pure phase, it is necessary to modernize former methods and develop new methods for synthesizing materials. As part of this study, a pulse magnetometer was made to study magnetic hysteresis loops. An exceptional feature of this device is the ability to conduct studies of the full cycle of the hysteresis loop using pulsed magnetic fields. M-type BaFe12O19 hexagonal ferrites were synthesized by standard ceramic, mechanochemical, and sol–gel methods. The structural, phase, and magnetic characteristics of the barium hexaferrites were studied. Methods for the synthesis of BaFe12O19 hexagonal ferrites were estimated and compared. Their structural and magnetic properties essentially depend on the method of synthesis. The mechanochemical technology makes it possible to obtain materials without impurity phases through the use of hydrated reagents in the synthesis. The use of sol–gel technology allows the synthesis to be carried out at much lower temperatures.

Keywords: radio-absorbing materials and coatings, composite materials, spectra of magnetic permeability and dielectric permittivity, reflection, absorption, and transmission coefficients, microwave range.Electromagnetic wave absorbers fabricated from radio-absorbing materials (RAM) are used in microwave technology to manufacture anechoic chambers, to protect personnel against the influence of microwave radiation, to manufacture matched loads for waveguide structures, and to mask radars [1]. Composite RAM whose matrix is formed by high-molecular polymer compounds and whose fillers are particles of ferro-or ferrimagnetic materials have found wide application [2]. These materials deposited on metal surfaces are effectively used as absorbers of electromagnetic waves.In [3][4][5][6] it was suggested to use carbonyl iron (FeC) powders for RAM in the microwave range. Investigations of the spectra of complex magnetic permeability ( i ′ ′′ μ = μ − μ ) and dielectric permittivity ( i ′ ′′ ε = ε − ε ) of composites with different filling factors at frequencies up to 18 GHz have demonstrated that these materials possess noticeable magnetic and dielectric losses and are promising for application as absorbers of electromagnetic waves in the microwave range. It has also been demonstrated that the two-layer RAM have smaller reflection coefficient and wider frequency band [4,6] in comparison with single-layer RAM [5]. They consist of a strongly absorbing layer deposited on the metal surface and a layer that matches the electromagnetic wave absorber with the free space having smaller values of the magnetic permeability and dielectric permittivity. The composite 0.94 mm thick comprising 50% (by volume) of P-10-grade carbonyl iron was an absorbing layer and the composite 2.2 mm thick comprising 15% of FeC was used in [6] as a matching layer. The frequency range in which the reflection coefficient was less than -10 dB extended from 2.9 to 16.8 GHz [6].It is well known [7] that the frequency range in which great magnetic losses are observed due to the phenomenon of natural ferromagnetic resonance in the presence of domain structure extends fromDue to the large value of iron saturation magnetization M S ≈ 1.7⋅10 3 G, this range extends from f 1 ≈ 1.4 GHz to f 2 ≈ 61 GHz. In calculations, γ/2π = 2.8 GHz/kOe and the anisotropy field H a ≈ 0.5 kOe were assigned. The above-mentioned estimates demonstrate that the composite materials based on carbonyl iron can have significant absorbing properties at frequencies of 20 GHz and higher. This work presents results of experimental investigations into the absorbing properties of composites comprising R-10-grade carbonyl iron powders in the polyethylene matrix for frequencies in the range 26-37 GHz. Samples with volume iron content of 15% (sample No. 1) and 50% (sample No. 2) were investigated.Measurements were performed using an R2-65 standing-wave ratio (SWR) meter with horn antennas 5 cm long and 2 ×1 cm 2 antenna aperture. To measure the transmission (T) and reflection coefficients (R) for a s...

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There is a growing demand for light and radar absorbing materials in both commercial and military purposes. In this paper, microwave properties of polimer based composites containing multiwalled carbon nanotubes used as fillers have been analyzed. The multiwall carbon nanotubes used in the composite were about 9.4 nm in diameter. The results show that the ultrasonic treatment modifies the dielectric properties of the composite. Both real and imaginary permittivity of composites is 2 times more than ordinary example after sonicating for 3 minutes.