Heat capacity of the PbFe1/2Ta1/2O3 perovskite-like compound

Physics of the Solid State - The heat capacity C p(T) of the complex perovskite PbFe1/2Ta1/2O3 has been studied using adiabatic calorimetry in the temperature range 150–370 K. Three diffuse...     

A study of the phase diagrams of (NH4)3Ga1−x ScxF6 ammonium cryolites

This paper reports on the results of analyzing p-T and x-T phase diagrams and calorimetric properties of solid solutions in (NH₄)₃Ga_1?x Sc_xF₆ cryolites with scandium concentrations x=0.0, 0.1, 0.35, 0.4, 0.6, 0.8, and 1.0. The thermodynamic parameters of the phase transitions observed in the studied compounds are determined. The generalized phase diagram and successive structural transformations in a series of (NH₄)₃ Me ³⁺F₆ ammonium cryolites are discussed.     

Ferroelastic phase transitions in (NH4)2TaF7

The heat capacity, unit cell parameters, permittivity, optical properties, and thermal expansion of the (NH₄)₂TaF₇ compound with a seven-coordinated anion polyhedron have been measured. It has been found that the compound undergoes two successive phase transitions with the symmetry change: tetragonal → (T ₁ = 174 K) orthorhombic → (T ₂ = 156 K) tetragonal. The ferroelastic nature of structural transformations has been established, and their entropy and susceptibility to hydrostatic pressure have been determined.     

An experimental study of the forerunners of boundary-layer localized disturbances at an enhanced turbulence level

Turbulence production processes in boundary layer at a high level of free-stream turbulence have been studied. The tests were carried out in the MT-324 subsonic wind tunnel of ITAM, SB RAS, on models of straight and 45° swept wings at Reynolds numbers Re_c1 = 97000 and Re_c2 = 137000, and also at low (Tu = 0.18 % U _∞) and high (Tu = 0.79 and 2.31 % U _∞) levels of free-stream turbulence. The longitudinal localized disturbances developing in the boundary layer under the action of free-stream turbulence were artificially modeled using local air suction through a slot on the model surface. Wave packets, or forerunners, produced in the boundary layer, in the region preceding the abrupt local change of flow velocity near the localized-disturbance fronts, were examined. The high level of free-stream turbulence was found to accelerate the downstream evolution of the wave packets and their transformation into turbulent spots.     

Effect of Sequential Heat Impacts on the Formation of a Stable State of the xLPM–(1 – x)PT Multiferroic Composites

Physics of the Solid State - The effect of thermal cycling and sintering temperature on the chemical and thermodynamic stability of the bulk multiferroic xLa0.7Pb0.3MnO3–(1 – x)PbTiO3...     

Simulation of ferromagnetic resonance in a rectangular microstrip

The results of the micromagnetic simulation of spectra and the spatial distribution of microwave magnetization oscillations in a rectangular ferromagnetic strip are discussed. It is shown that resonance oscillations have a complex spatial structure which is the composition of quasiuniform precession, longitudinal spin-wave resonance, and localized edge modes.     

Ferromagnetic resonance in interacting magnetic microstrips

The results of the micromagnetic simulation of forced oscillations of the magnetization in a system of two interacting microstrips located at an angle to each other have been presented. The ferromagnetic resonance spectra and the mode composition of resonant oscillations of the system have been investigated under the conditions of magnetostatic and exchange interactions between the microstrips. It has been shown that the magnetostatic interaction leads to the possibility of the excitation of in-phase and out-of-phase coupled oscillations of the magnetization of the microstrips. In the systems of exchange-coupled microstrips, there are intense resonances due to oscillations of the domain walls. The transformation of the ferromagnetic resonance spectrum and the change in the mode composition of resonant oscillations in different equilibrium configurations of the magnetization of the system have been discussed, as well as the conditions for the excitation of oscillations of different types depending on the direction of the microwave magnetic field.     

Disorder and phase transitions in oxyfluoride (NH4)3Ta(O2)2F4

Calorimetric, X-ray, dielectric and DTA under pressure measurements have been performed on oxyfluoride (NH₄)₃Ta(O₂)₂F₄. The succession of nonferroelectric phase transitions was found associated with the order-disorder processes. The comparative analysis tantalate with related niobate has revealed the important role of the central atom in the physical properties behavior, mechanism of structural distortions and barocaloric effect in oxyfluorides with the eight-coordinated anionic polyhedra.