Low-temperature thermodynamics of the two-dimensional orbital antiferromagnet

We consider the low-temperature properties of a two-dimensional orbital anti-ferromagnet (OAF), which is one of the possible states of the weakly interacting electron system with a half-filled band on a square lattice. Such a state can result from anisotropic electron-hole pairing due to the nesting property of the Fermi surface, and is characterized by nonzero local currents violating translational symmetry of the underlying lattice. Within a simple mean-field model, we show that, in the low-energy limit, the 2D OAF is described by (2+1)-dimensional quantum field theory of gapless fermion excitations associated with zeros of the gap function. The relativistic Landau quantization of the spectrum in external magnetic field shows up in unusual behavior of the magnetic susceptibility. Strong diamagnetism of the OAF is found in the perpendicular field, changing to paramagnetism upon the decreasing of the angle between the field and the plane. When the angle approaches zero, the susceptibility shows an oscillatory angle dependence.     

Aspects of making a superconducting yttrium ceramic by self-propagating high-temperature synthesis

Macrokinjetic features are considered for the combustion in oxygen of BaO₂–Cu–Y₂O₃ mixtures, which produces the high-temperature superconductor yttrium barium cuprate YBa₂Cu₃O_7–x. Studies have been made on how the initial temperature affects the combustion temperature and rate, and the critical temperature for self-ignition has been determined. Ultrasonic activation of the initial powders has an advantageous effect on the product quality. Thermal analysis has been applied to the activated mixtures, which indicates the reason for the rise in burning wave propagation rate and increase in conversion to the superconducting phase.Chernogolovka. Translated from Fizika Goreniya i Vzryva, Vol. 29, No. 2, pp. 62–67, March–April, 1993.     

Examination of the first unit at the armenian nuclear power station after the end of operation

Moscow Physics Research Institute. State Atomic Inspectorate Scientific Center. Moscow Special Research Institute. Armenian Nuclear Power Station. Institute for Atomic Energy. Dekom Cooperative. All-Union Nuclear Materials Research Institute. Gidropress Special Designs Office. Translated from Atomnaya Énergiya, Vol. 72, No. 4, pp. 345–353, April, 1992.     

Characteristics of Armenian Magavuzsk coal

Armenian Magavuzsk coal is studied by chemical, thermal, and physicochemical methods (technical and elementary analysis, heat of combustion, mineral characteristics, petrographic composition, clinkering properties, oxidation, mechanical strength, and thermal stability). The coal is classified in terms of its genetic and technological parameters and the uses consistent with its quality.     

A new route to synthesize La1?xSrxMnO3

Self-Propagating High-temperature Synthesis (SHS) was used to producecomplex oxides (La_1–x Sr _x MnO₃ with x = 0, 0.1 and 0.2), which are used as the cathode in solid oxide fuel cells (SOFCs). Thermodynamic predications and experiments show that La_1–x Sr _x MnO₃ can be prepared via SHS under moderate conditions from a mixture of La₂O₃ + SrO₂ + Mn, using either gaseous oxygen or solid NaClO₄ as the oxidant. Partial melting at the high combustion temperature increased product homogeneity. The electrical conductivity of the product was 180 S·cm^–1 at 1000°C in air, matching that of sample made by other synthesis processes. SHS enables a more economical production of La_1–x Sr _x MnO₃ than existing commercial processes.     

Synthesis of LiTaO3 in self-propagating high-temperature wave

Chernogolovka. Translated from Fizika Goreniva i Vzryva, Vol. 29, No. 1, pp. 62–67, January–February, 1993.     

Phase Formation during Self-Propagating High-Temperature Synthesis of Ferrites

Phase formation during self-propagating high-temperature synthesis of ferrites was studied. The sequence of phase changes was established, and the intermediate phases were identified. The structure and properties of the synthesized ferrites were investigated.     

Low-temperature thermodynamics of a one-dimensional interacting Fermi system

Using the exact solution of theSU(2) Thirring model, we derive an infinite set of coupled nonlinear integral equations describing the thermodynamic properties of a one-dimensional Fermi gas at a given temperature and magnetic field. The limiting case ofT=0 is considered, in which the magnetic field dependence of the ground state energy is calculated for both repulsive and attractive interactions.