On the magnetic properties of mechanosynthesized Co-Fe-Ni ternary alloys

X-ray diffraction, Mössbauer spectroscopy and magnetization measurements were used as complementary methods to obtain structural data and to determine magnetic properties of the mechanically synthesized and subsequently thermally treated Co-Fe-Ni alloys. New, however approximate, phase diagrams were established on the basis of X-ray diffraction investigations. Mössbauer spectroscopy and magnetization measurements allowed to reveal practically linear correlation between the average values of the hyperfine magnetic field induction, 〈B_hf〉, and the effective magnetic moments, μ_eff, of the alloys. The decrease in 〈B_hf〉 with the number of electrons per atom, e/a, was observed. Moreover, the dependence of μ_eff on the valence 3d and 4s electrons per atom follows the Slater-Pauling curve. Thermal treatment of mechanosynthesized Co-Fe-Ni alloys led to some changes in the phase diagrams, increase in the grain size and decrease of the level of internal strains in alloys. Dependencies of lattice constants, average hyperfine magnetic fields, effective magnetic moments and Curie temperatures on the number of electrons per atom have the same trends for mechanically synthesized as well as for thermally treated alloys.     

On the self-consistent statistical theory of vacancies

We report here a new method of describing the effect of the presence of vacancies on the structure, dynamics and thermodynamics of a crystal. The unsymmetrized self-consistent approximation is used to determine the potential energy in which the defective structure and the anharmonicity appear from the beginning. In order to stress the power of this method, we calculate the free energy of formation of a vacancy and the concentration of vacancy in a two-dimensional triangular Lennard-Jones crystal. A comparison with Monte Carlo simulation is given and a possible application to experimentally accessible systems is discussed.     

The theory of atomic and magnetic ordering in ternary alloys with fcc lattice

We consider the theory of the mutual influence of atomic and spin ordering phenomena in ternary alloys of transition elements with fcc lattice. The case of quasibinary alloys B₃A-B₃D is considered in detail. Concentration dependences of the critical temperature of the order-disorder phase transition are considered for cases of atomic and magnetic ordering.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 48–57, December, 1970.     

On a statistical theory of overlapping resonances

The statistics of unstable N-level quantum systems is considered. The distribution function for complex energies and the density of overlapping resonances are obtained. It is shown that the instability removes the level repulsion at energy differences less than the width whereas the complex energies repulse quadratically. In the case of strong level—channel-coupling, k “collective” states (k is the number of channels) are formed, absorbing the total width.     

On the simple-source theory of sound from statistical turbulence

A theory for the generation of aerodynamic sound, stated in terms of convected simple sources and dipoles, is presented. The sources are found to depend upon convective derivatives of the hydrodynamic pressure within the turbulent source region. The results are similar to earlier efforts involving simple sources, sometimes called dilatational sources. The results are modified for effects involving measurements on moving flows. The theory shows explicitly the refractive effects of shear flow within the source region, as well as of temperature changes (if any) within the source region. The oscillating cylinder problem is discussed and the results of the present theory are found to agree with those obtained by Lauvstad using a matched asymptotic expansion for the same problem. The theory is used to predict the temperature dependence of sound power for hot jets.Consultant for Bolt Beranek and Newman, Inc.     

Quasibinary ordering of ternary alloys

The problem of ordering in ternary alloys is considered for the case when a partially ordered phase is formed (quasibinary configuration of a ternary alloy). A. G. Khachaturyan's method is used to construct possible functions for the distribution of atoms over the points of the crystal lattice. A possible ternary superlattice is predicted for the case when the quasibinary configuration corresponds to the superlattice B2, L1₂, L1₀.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 63–68, March, 1976.     

Order-disorder transformation theory in ternary alloys with face-centred cubic lattice-I.: Equilibrium equations

The atomic ordering of the L 1₂ binary superstructure type in a ternary alloy is investigated. The equilibrium equations of the alloy are given according to the Kikuchi approximation with the account of the atomic interaction energy and the correlation in the first coordination sphere.     

Thermodynamic properties of ternary semiconducting alloys

Using the new information supplied by extended-x-ray-absorption-fine-structure measurements and the results of our structural model, we compute the bond probability of a few ternary semiconducting III–V and II–VI alloys as a function of temperature and composition in the framework of a modified quasi-chemical approximation. We derive the thermodynamic functions of mixing, considering both elastic and chemical contributions to the bond energies. We examine how the deviation from the full randomness affects the ordering of such alloys and we construct the phase diagrams in the region of phase separation. Possible formation of ordered compounds at low temperatures is predicted.     

On the statistical theory of spatial structure formation in random media

It is shown that, in parametrically excited stochastic dynamic systems described by partial differential equations, space structures (clustering) can be formed with probability 1 due to rare events occurring with probability tending to zero. Such problems arise in hydrodynamics, magnetohydrodynamics, plasma physics, astrophysics, and radiophysics. … Chaos is the place which serves to contain all things; for if this had not subsisted neither earth nor water nor the rest of the elements, nor the Universe a whole, could have been constructed… Sextus Empiricus, Against the Physics, against the Ethicists, R. G. Bury, p. 217, Harvard University Press, 1997.     

Pair effects in disordered ternary alloys

A generalization of the coherent potential approximation and its diagrammatic equivalent have been used to include pair effects in the electronic self-energy of compositionally disordered-model ternary alloys.     

Metastable states in ternary ordered alloys

The Gorskii-Bragg-Williams approximation is employed in a theoretical study of certain features in the atomic distribution in ternary ordered alloys having fcc lattices. The effect of various parameters in the interatomic interactions and of the concentration of the third alloying element are studied for their influence on the formation of metastable states in these alloys.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii Fizika, No. 6, pp. 31–34, June, 1971.     

Ordering of ternary alloys in the self-consistent field approximation

In the self-consistent field approximation, without allowance for correlation, a static theory of the ordering of ternary alloys is constructed which makes it possible to take into account the long-range nature of the interatomic interaction forces in substitutional and interstitial alloys. The theory enables one to take into account the possible existence in the alloy of two subsets of points differing by the species of atoms that occupy them. The stability of the disordered state in such alloys is analyzed and an expression obtained for the temperature at which the disordered state loses stability.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 61–64, November, 1980.     

Thermodynamic and statistical studies of supersaturated ternary solutions

The influence of chromium ions Cr3+ on properties of supersaturated aqueous solution of ammonium sulfate (NH4)2SO4 has been studied employing containerless electrodynamic levitation of single microdroplets of this solution with known concentration of Cr3+ ions. The water activity versus solute concentration was measured in three different sets of experiments corresponding to different initial concentrations of Cr3+ ions. Theoretical treatment of the experimental results obtained is developed employing the theory of supersaturated electrolyte solutions [Phys. Rev. E 52, 1325 (1995)]. This treatment has allowed the following two conclusions. First, spinodal concentration is a decreasing function of Cr3+ concentration. Second, solute clusters formed in the presence of Cr3+ ions demonstrate complex behavior with respect to binding water molecules: (a) at low and moderate supersaturations, they bind more water molecules than clusters formed in the absence of an impurity; and (b) at high supersaturations, they bind less water molecules than clusters formed in the absence of an impurity.     

Ordered-disordered ternary alloys by atomic layer epitaxy

Ga₀₅In₀₅P ternary alloys, lattice-matched to GaAs substrates, were grown by atomic layer epitaxy. The growth proceeded by the deposition of monolayers of In-P-Ga-P in a self-regulated fashion. The ternary alloys were found to have different crystal and bandgap structures depending on the growth conditions. Films deposited on (1 0 0) oriented GaAs substrates have a random (disordered) structure withE _g 1.9 eV. However, the same ternary alloy deposited on misoriented substrates showed a high degree of ordering withE _g 1.76 eV. The ordered structure is in the form of highly strained monolayer superlattices (InP-GaP) oriented along the (1 1 1) direction. The ordered-disordered transition can also be achieved by Se doping to the 10¹⁷ cm^–3 range. We report on the atomic layer epitaxy growth conditions for both ordered and disordered GaInP films. We also discuss several possible quantum well structures based on this ternary alloy.     

On a class of integrals appearing in the theory of statistical nuclear reactions

In a recent issue of Annals of Physics, Verbaarschot discussed the results of the random matrix theory of statistical nuclear reactions. When the Hauser-Feshbach limit of this theory is considered, a certain class of definite integrals appears. Verbaarschot has given their numerical values. We correct some of his results and describe an analytic and more general way to evaluate the integrals.     

Electrical resistivity of liquid binary and ternary alloys

New method of calculation of the electrical resistivity of liquid and amorphous alloys is presented. The method is based on the Morgan–Howson–S̆aub (MHS̆) model but the pseudopotentials are replaced by the scattering matrix operators. The Fermi energy is properly determined by the accurate values of the phase shifts. The model depends on a very small number of universal parameters and gives stable results. The calculated values of the resistivity agree well with available experimental data for a substantial number of binary alloys. Moreover, the results for some ternary alloys were also obtained.     

Onset of magnetism in concentrated ternary alloys I

The onset of magnetism and the magnetic propreties of concentrated substitutional ternary alloys A(Fe_1?xB_x)₂ (A = Y, Zr, U; B = Mn, Co, Ni and Al), Y₂(Ni_1?xCo_x)₇, Y(Ni_1?xCo_x)₃, Y₆(Fe_1?xMn_x)₂₃ and Ti(Fe_1?xCo_x) as well as the amorphous alloy system (Fe_1?xNi_x)₇₇Si₁₀B₁₃ are discussed in terms of homogeneous and heterogeneous models based on the Stoner-, Edwards- Wohlfa arth- and the Landau theory of phase transitions of second order. For a detailed comparison of the nine ternary systems A(Fe, B)₂ (A = Y, Zr, U; B = Mn, Co, Al) we refer to a following paper. From the results obtained on alloying UNi₂ with Fe, Co and Cu we propose that the magnetic moment of UNi₂—contrary to UFe₂—resides mainly on U rather than on the Ni site. The appearance of magnetism in YNi_x compounds by either changing the Y : Ni ratio or substituting Ni by Co in YNi₃ and Y₂Ni₇ is mainly attributed to band effects for which a schematic N(E) curve is proposed. The breakdown of long-range magnetic order in Y₆(Fe, Mn)₂₃ seems to be caused by a lack of delocalized electrons and a preferential site occupation of Mn and Fe. The magnetic properties of Ti(Fe_1?xCo_x) change from an itinerant to a localized moment behaviour above and below x = 0.5 due to the occurrence of Fe antistructure atoms which drive the onset of long-range magnetic order. The occurrence of magnetism in amorphous alloys compared with that of crystalline alloys with a high degree of disorder may be characterized in a similar way.     

On the statistical properties of energy levels in quantum theory of axial channeling

The energy levels of electrons moving in the mode of axial channeling in a system of parallel chains of atoms (chains of the Si[110] crystal are used as an example) are found numerically in this paper. The obtained distributions of intervals between neighboring energy levels in the quasiclassical region are compared with predictions for systems demonstrating regular and chaotic behavior at the classical limit.