arXiv subjects

V. N. Varyukhin

Publications and source records attributed to V. N. Varyukhin.

7 recordsLinked to original sources

arXiv2014

Effect of the techniqie of drawing with shear on the structure and the properties of low-carbon wires

The technology of drawing with shear is developed. It allows increasing technological plasticity of low carbon steel without heat treatment. It is found that the use of experimental technology can improve mechanical properties of wire samples with the diameter reduced during drawing: the relative reduction of the wire decreases slightly and remains at high level compared with the classical technology, where the relative reduction in the course of drawing drops more than twice. It is shown that the use of experimental technology allows varying the size of a ferrite grain (increase or decrease) compared with the classical technology, where increasing of deformation degree results in grain reduction. Furthermore, the experimental technology allows reducing the number of pores in a wire of small diameter. To prevent heating of the wire and the drawing dies, it is proposed to use experimental drawing through two experimental dies with shear separated by an ordinary die. As a result, the workability of the process will be enhanced and the efforts of drawing will be reduced.

cond-mat.mtrl-sci↗

arXiv2012

Lattice dynamic theory of compressed rare-gases crystals in the deformed atom model

Lattice dynamics of rare-gas crystals is built on the base of adiabatic approximation when the deformation of electron shells of atoms of dipole and quadrupole types depending on nucleus shift and simultaneously arising Van-der-Vaals forces. The dipole forces are the most long-range ones. The obtained oscillation equations are studied in long-wave approximation. The role of three-body interaction and quadrupole deformation in the violation of Cauchy relation is discussed. Birch elastic moduli calculated for Xe and deviations from Cauchy relation are in good agreement with the experiment in a wide pressure range.

cond-mat.other↗

arXiv2011

Optimum oxygen content in La0.7Sr0.3MnO3 thin films

The technological conditions of oxygen content variation in epitaxial La0.7Sr0.3MnO3-δ films and the peculiarities of change of their transport characteristics were investigated. The films were grown onto single crystal SrTiO3 substrates by an enhanced method of dc magnetron sputtering of a ceramic target. It was revealed, that the oxygen content of the film material with initially strong deviation from stoichiometric composition (δ>0.06) changes easily in both directions at temperatures Tp >=870 K, and the result of the oxygen content variation can be well controlled via changes of conductivity minimum temperature (Tm). The particularities of indirect accurate control of the oxygen content in the film are described. The existence of oxygen-excessive composition of the film is in principal agreement with the known phase diagrams for a powder samples. It was revealed, the oxygen-excessive content of the film causes the increase of free charge carriers concentration and the decrease of the film conductivity in ferromagnetic state. It is shown, that the oxygen-deficient films can demonstrate the same peculiarity of magnetotransport properties as the films with a deviation from stoichiometric content in cation composition.

cond-mat.mtrl-sci↗

arXiv2010

Selected aspects of the condensed matter physics. Work and life of Professor B.Ya. Sukharevsky

The paper contains a short description of the scientific papers of Professor Boris Ya. Sukharevsky on condensed matter physics. His basic scientific activity was related to following directions: structural vacancies concept; influence of point defects on statics and kinetics of phase transitions; DNA crystallization and low-dimensional systems properties; phase transitions in Jahn-Teller crystals; Thermophysics of superconductors e.a. The list of most essential papers of Prof. B.Ya. Sukharevsky is included.

cond-mat.mtrl-sci↗

arXiv2005

Andreev Reflection and Long-Range Proximity Effect in Pb/LaCaMnO Point Contacts

The Andreev reflection (AR) spectroscopy has been used to probe mutual influence of superconducting pairing and ferromagnetic correlations in contacts of low-temperature superconductor (S), Pb, and half-metallic ferromagnetic, La0.65Ca0.35MnO3(LCMO). Two different AR spectra have been observed. In the contacts without proximity effect, the AR spectra reveal a behavior typical for superconductor/spin-polarized metal contacts. In the contacts, which we distinguish as the proximity affected ones, a few unusual effects have been detected. Namely, we have observed: (i) a spectacular drop in the resistance of the contacts at the onset of the Pb superconductivity; (ii) a typical for S/normal nonmagnetic metal contacts, excess current and doubling of the normal-state conductance; and (iii) a much larger than it should be for conventional superconductivity ratio of the single-particle gap to the Pb superconducting transition temperature. The very distinct AR characteristics of proximity affected contacts observed by us suggest unconventional (triplet) superconducting pairing and long-range proximity effect at S/LCMO interface.

cond-mat.supr-con↗

arXiv2005

Magnetism via superconductivity in SF proximity structures

We consider the proximity effects in hybrid superconductor (S) - ferromagnet (F) structures drawing attention to the induced ferromagnetism of the S metal. The analysis is based on a quasiclassical theory of proximity effect for metals in the dirty limit conditions. It is shown that, below the superconducting critical temperature, ferromagnetic correlations extend a distance of order of the superconducting coherence length ξ_{S} into the superconductor, being dependent on the S/F interface parameters. We argue that the properties of mesoscopic SF hybrids may drastically depend upon the magnetic proximity effect, and recent experiments lend support to the model of SF structures where the superconducting and magnetic parameters are tightly coupled.

cond-mat.supr-con↗

arXiv2004

Point-contact spectroscopy of magnesium diboride with different counter-electrodes

We report on tunneling and Andreev-reflection conductance spectra of 39 K superconducting magnesium diboride, obtained with Pb and Au counter-electrodes. Two distinct steps at close to 2.7 and 7.1 meV appear in a low-resistance metallic-type Au-MgB2 junction characteristic, whereas a tunneling-like spectrum measured for the same junction, annealed by the application of dc current, exhibits only a rounded contribution of the larger gap. Junctions with a superconducting lead counter-electrode pressed into a bulk MgB2 sample reveal two conductance peaks that are interpreted as the result of the formation of highly-transmitting break junctions inside the magnesium diboride ceramic. Our results strongly support the two-band model with two different gap values on quasi-two-dimensional σ(7.1 meV) and three-dimensional π(2.7 meV) Fermi surface sheets of MgB2.

cond-mat.supr-con↗