Eugene P. Yelsukov

Mössbauer study of magnetic properties formation in disordered Fe-Al alloys

Abstract For by mechanical treatment disordered Fe-Al alloys in the concentration range of Al from 0 to 60 at% the average hyperfine field, H , and isomer shift, η , values, the magnetic ordering temperatures Tc and the average magnetic moment m per Fe atom were measured in Mossbauer and magnetometric studies. An explanation for the features of the concentration dependence H (x) is proposed in terms of the local hyperfine field HK dependence obtained experimentally, and the local atomic environments probabilities. Proceeding from the data concerning the behaviour of the average and local hyperfine fields and the local atomic configurations, a model for the local magnetic moments mK on the Fe atom, which describes the form of the average magnetic moment m as a function of Al content, was constructed.

Structure and magnetic properties of Fe100-xSnx (3.2 < × < 62) alloys obtained by mechanical milling

Abstract The structure and magnetic properties of mechanically ground Fe-Sn alloys have been studied by X-ray diffraction, magnetic measurements, and 57Fe and 119Sn Mossbauer spectroscopy. It has been shown that the alloys are nanocrystalline and have the disordered bcc structure with Sn concentrations x 32.7. The concentration dependences of the magnetic ordering temperature, average magnetic moment per Fe atom, average hyperfine magnetic field and isomer shift, as well as those of the bcc lattice parameter and grain size are nonlinear and reveal a number of peculiarities at 12–15, 25 and 50 at% Sn. The ferromagnetic state is shown to form in alloys with x

Hysteresis magnetic properties of the Fe(100−x)C(x); x=5–25 at% nanocomposites as-mechanically alloyed and after annealing

Abstract The paper presents the results on coercive force and specific saturation magnetization depending on the phase composition and grain size of the Fe–C powders after mechanical alloying and subsequent annealing.

Average and local magnetic moments on Fe atoms in microcrystalline and amorphous Fe100−xPx alloys

Abstract We have measured the concentration dependence of the average magnetic moment per Fe atom mFe(x) in microcrystalline and amorphous Fe-P alloys obtained over a wide concentration range using electrochemical deposition. The model of local magnetic moments has been used to described mFe(x). On the basis of this model the effects of phosphorus on the value mFe are explained in terms of the parameters of the local environment of the Fe atom.

Magnetic properties of amorphous Fe78P22 alloy obtained by mechanical grinding

Abstract The amorphous Fe 78 P 22 alloy obtained by mechanical grinding was studied by X-ray analysis, Mossbauer spectroscopy and magnetic measurements. The measured values of the average hyperfine magnetic field H , mean magnetic moment per Fe atom m Fe and Curie temperature T c agree with those obtained earlier for electrodeposited and then ground samples and are in good qualitative agreement with the model describing macroscopic characteristics through the parameters of local environment but essentially disagree with the literature data for the samples obtained by rapidly quenching and only by electrochemical deposition.

Effect of silicon on the phase formation in mechanically activated systems based on Fe75C25: Mechanosynthesis of composite states

The methods of X-ray diffraction analysis, Mögsbauer spectroscopy, and measurement of dynamic magnetic susceptibility have been used to study stationary phase states that develop at the later stages of mechanical alloying in a planetary ball mill. In the Fe(100 − x)C(x), Fe(75)C(25 − x)Si(x), and Fe(75 − x)C(25)Si(x) (x ≤ 25) systems, the processes of phase formation are determined by the dynamic equilibrium between the crystalline and amorphous phases. Depending on the composition of the alloys, the conditions of this equilibrium are changed, which is reflected in the sets of the crystalline phases that are formed.

Frequency-Dependent Effective Material Parameters of Composites as a Function of Inclusion Shape

© 2012 Rozanov et al., licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Frequency-Dependent Effective Material Parameters of Composites as a Function of Inclusion Shape

Microwave Properties of Mechanosynthesized Fe-Paraffin Nanocomposites

The structure and microwave properties of composites consisting of paraffin as a dielectric host matrix and Fe particles as inclusions have been studied. The composites were prepared by the mechanochemical synthesis and contain 7.7% vol. concentration of the inclusions. The microwave properties were studied in 0.1 to 6 GHz frequency range. The microwave properties of the composites are shown to depend mostly on the size and shape of the inclusions, with the phase composition of the inclusions exerting only a slight effect. With decreasing the inclusions size, the low-frequency peak (300−400 MHz) attributed to the domain wall motion diminishes.

EXAFS investigation of the local atomic structure of Fe-Ge nanocrystalline disordered alloys

This paper reports on the results of EXAFS investigations (Fe K and Ge K absorption edges) of binary supersaturated nanocrystalline solid solutions Fe100−xGex (x = 15–40 at % Ge) prepared by mechanical alloying. The nanocrystalline disordered structure of the single-phase alloys is characterized using X-ray diffraction, Mössbauer spectroscopy, and magnetic measurements. The EXAFS spectra are analyzed by solving the inverse binary problem with the use of combined data on the Fe K and Ge K absorption edges. The parameters of the partial pair correlation functions obtained indicate that the crystal lattice is characterized by strong local static distortions and short-range chemical order increasing with an increase in the germanium content. Moreover, the formation of a hexagonal-type macrostructure in the body-centered cubic (bcc) lattice occurs through a “local” stage.

Effect of the nanocrystalline state and electrical resistance of Fe and Fe75Si25 powders produced by the method of high-energy ball milling on the frequency dispersion of microwave material parameters

The influence of the nanocrystalline state of Fe and Fe75Si25 particles and their electrical resistance on the microwave properties of composite materials that contain these particles has been investigated experimentally. The main factors that determine changes in the frequency dispersion of the permeability are the skin effect and the decrease in the internal field of anisotropy of the particles. In the case of Fe particles, the role of skin effect of prevails.