Study of magnetic properties of Pd<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>Fe<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>)<Subscript>0.95</Subscript>Mn<Subscript>0.05</Subscript> alloy using polarized muons and neutrons

The Pd_1?x Fe _x )_0.95Mn_0.05 alloy with random competing interaction was studied by measuring the muon spin relaxation in an external transverse magnetic field and in a zero magnetic field. Using the measured temperature dependence of the dynamic relaxation rate λ and the characteristics of the distribution of local static fields, the phase states of the sample under study are refined. In particular, it is shown that the ferromagnetic and spin-glass states coexist simultaneously in the sample below 25 K. Combined studies of the sample using the μSR and neutron depolarization methods made it possible to determine the size of magnetic inhomogeneities to be 2–6 μm in the temperature range 5–40 K.     

Influence of the growth mechanism and thermoelastic stresses on the lattice dynamics of heteroepitaxial films of barium strontium titanate

Heteroepitaxial thin films of Ba_0.7Sr_0.3TiO₃ (BST-0.3) solid solutions were grown on single-crystal (001) MgO substrates by high-frequency cathode sputtering of a stoichiometric ceramic target. The parameters of the tetragonal unit cell of a film were determined by x-ray diffraction methods, and the temperature dependence of the parameter c was studied depending on the synthesis conditions in the temperature range 293–520 K. An E(TO) soft mode was observed in the Raman spectra, the frequency of which correlates with two-dimensional stresses arising in films. It is shown that the two-dimensional stresses in a film are controlled not only by the film-substrate lattice constant mismatch and the difference of their thermal expansion coefficients but also are significantly dependent on the heteroepitaxial growth mechanism. It is shown that the phase transition to the tetragonal paraelectric phase during film heating occurs irrespective of the growth mechanism.     

Transport and ferromagnetism in InGaAs quantum well structures delta-doped with Mn

Samples containing InGaAs quantum wells with p-type conductivity delta-doped by Mn were synthesized and studied. Magnetic moment measurements on a SQUID magnetometer revealed the presence of ferromagnetism at temperatures T from 4.2 to 400 K. Anomalous Hall effect caused by additional sample magnetization was observed at temperatures of from about 30 to 80 K. The Shubnikov-de Haas effect was recorded at 4.2 K. Negative magnetoresistance changed sign for positive at T ≈ 30 K as the temperature increased.     

Mechanism of current flow in alloyed ohmic In/GaAs contacts

A mechanism of current flow in an alloyed ohmic In contact to low-doped gallium arsenide (n = 4 × 10¹⁵ cm^?3) is studied. From the temperature dependence of the contact resistance per unit surface area, it is found that the basic mechanism of current flow is thermionic emission through a potential barrier 0.03 eV in height.     

Evaluating the PT-violation contributions and the T-invariant masking spin-angle correlations in 10B(n, α1γ)7Li reaction

A three-vector a _pt (σ _n [k _α × s _γ]) correlation of the neutron beam polarization directions σ _n , α-particle momentum k _α, and γ-quantum circular polarizations s _γ in ¹⁰B(n, α₁γ)⁷Li reaction (E _γ = 478 keV) is proposed as a means of searching for the simultaneous time-reversal invariance and space parity (PT-invariance) violation. An expression for a _pt coefficient in the αγ cascade is presented. Masking effects, sensitivity of the proposed experiment, and its realization prospects are discussed.     

Return to foundations of wave optics

The Huygens-Fresnel wave principle is found to extend far beyond its traditional use. Using only elementary mathematical means, it is shown in particular that this principle suffices to provide the exact solution of Sommerfeld's problem of plane wave diffraction by a perfectly conducting half-plane. A more exact formulation of the wave principle itself is proposed.     

Reversed steric order of reactivity for tert-butyl and adamantyl-3-cyanomethylene-1,2,4-triazines

Reactions of 2-(6-tert-butyl-5-oxo-4,5-dihydro-1,2,4-triazin-3(2H)-ylidene)-3-oxo-3-R-propanenitriles (R = t-Bu, Ad-1) with tert-butyl bromoacetate gave the corresponding N(2), C(5)O bis-alkylation products. Treatment of the latter with t-BuLi, in the case of R = t-Bu, led to intramolecular condensation at the exocyclic nitrile group. However, in the case of R = Ad-1, the condensation with the sterically more hindered carbonyl group was observed to give diastereomerically pure 8-cyanopyrrolo[1,2-b][1,2,4]triazine-6-carboxylate derivatives. The structures of the isolated products were confirmed by spectral methods and X-ray single-crystal diffraction.     

Gas-Phase Hydrodechlorination of Chlorobenzene over Alumina-Supported Nickel Catalysts: Effect of Support Structure and Modification with Heteropoly Acid HSiW

Kinetics and Catalysis - The physicochemical and catalytic properties of 6%Ni/Al2O3 catalysts in the gas-phase hydrodechlorination of chlorobenzene (CB) are studied. The catalysts are synthesized...     

Approximability of HNN-extensions with central associated subgroups by a root class of groups

HNN-extensions of a group with central associated subgroups are considered. Several conditions are obtained for the approximability of such HNN-extensions by a class of groups which have the root property and is closed with respect to factorization.     

Effective temperature scattering matrix and kinematic mechanism of cooper instability in antiferromagnetic rare-earth intermetallides

An effective temperature-dependent scattering matrix for a localized subsystem is obtained in the periodic Anderson model by summing itinerant variables in the diagrammatic series of perturbation theory. The effective interaction that occurs in this case can lead to an antiferromagnetic phase, a superconducting phase, and the phase of coexisting superconductivity and antiferromagnetism observed in heavy-fermion intermetallic compounds.