Supersolid magnetic phase in the two-dimensional Ising-like antiferromagnet with strong single-ion anisotropy

The Ising model with the frustrated exchange interaction for strongly anisotropic antiferromagnetic ultrathin film is investigated in the mean field approximation at low temperatures. It is shown that a spatially inhomogeneous state can be accomplished in the system at a certain relation of material constants values, along with homogeneous states: ferromagnetic, quadrupolar or supersolid magnetic phases. The phase diagram of the system is built on the basis of stability lines analysis.     

Phase transitions in 2D and 3D non-Heisenberg ferromagnets with temperature-dependent anisotropy

A model of a non-Heisenberg ferromagnet is considered in which the single-ion anisotropy constant is linearly dependent on temperature. The conditions are found under which phase transitions occur in 2D and 3D non-Heisenberg ferromagnets as the temperature is varied. It is shown that, in the case where the biquadratic interaction is dominant, quadrupole states can occur in the system, which are specified by the orientation of the quadrupole moment. As the temperature is varied, a phase transition between quadrupole states can occur in 2D magnets. Depending on the ratios between the material constants, this transition can be either a second-order phase transition with the continuously changing orientation of the principal axes of the quadrupole moment tensor or a first-order phase transition with hysteresis through a state with a nonhomogeneous distribution of the principal axes of the quadrupole moment tensor. In 3D magnets, the phase transition between quadrupole states is of the first order with hysteresis. Phase diagrams of the system are constructed.     

Phase diagram of Fe1−xCox ultrathin film

Concentration-driven reorientation phase transitions in ultrathin magnetic films of FeCo alloy have been studied. It is established that, in addition to the easy-axis and easy-plane phases, a spatially inhomogeneous phase (domain structure), a canted phase, and also an “in-plane easy-axis” phase can exist in the system. The realization of the last phase is associated with the competition between the single-ion anisotropy and the magnetoelastic interaction. The critical values of Co concentration corresponding to the phase transitions are evaluated, the types of phase transitions are determined, and the phase diagrams are constructed.     

Layers of cyclam-substituted PVC with sodium hydroxide aqua complexes with aza-crown ligands on cellulose tissue filled with active coal

A material with an electrically ОН^–-conductive porous layer of cyclam-substituted PVC filled with active coal containing NaOH aqua complexes with aza-crown ligands and cross-linked with the surface of cellulose tissue fibers has been synthesized. The structure of the material was studied. Its sorption capacity in vapors and liquid benzene and hexane, specific resistance, potential of ОН^- transfer from solution to layer, and rate constants of ОН^– travel in the layer of the material as an electrochemical bridge in vapors and liquid benzene and hexane were determined. The aqua complexes decomposed in the layer with formation of Н₂ during the cathodic polarization of the bridge and О₂ during the anodic polarization; the composition of the complexes was regenerated due to the motion of ОН^–.     

Disproportionation of olefins on modified aluminum-rhenium catalysts

Conclusions The promotion of an aluminum-rhenium catalyst, containing 0.2–0.5% of Re₂O₇, by molybdenum oxides and tetraalkylstannanes increases its activity substantially in the disproportionation of olefins.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1623–1625, July, 1979.     

Centrifugal instability in rotating shallow water and the problem of the spiral structure in galaxies

A new instability predicte by theory to occur in rotating shallow water in which the rotation velocity has a discontinuity, in a regime where the flow velocity exceeds the characteristics velocity of the waves, has been found experimentally. The instability develops when the radial gradient of the angular velocity across the discontinuity is negative; such an instability is likely to be responsible for the formation of the spiral structure in galaxies which have a similar rotational velocity profile.     

Skin effect in massive conductors used in pulsed electrical devices: II. Massive conductors in electric circuits

Approximate relationships between the current and voltage drop across a set of massive conductors are established. They include two constant parameters: external inductance L of the conductors and skin parameter S. Specific shapes of the voltage across the massive conductors are illustrated with oscillograms. Mathematical processing of current and voltage oscillograms to estimate L and S is developed.     

On an approach to the design of reinforced shells that is optimal in terms of reliability

We consider questions of optimal design of shallow spherical shells reinforced by a grid of struts taking account of reliability. It is assumed that the independent random variable acting on the structure is distributed according to the Weibull law.Translated fromMatematicheskie Metody i Fiziko-Mekhanicheskie Polya, Issue 36, 1992, pp. 60–63.