Influence of the prehistory of NaNbO3-Gd1/3NbO3 ceramics and single crystals on their dielectric properties

The dielectric properties of a ceramic and a single crystal of the same composition 0.9NaNbO₃-0.1Gd_1/3NbO₃ (NNG10) with different prehistories of the material are investigated in the low-and infralow-frequency ranges. It is revealed that the dielectric aging of the material based on the NaNbO₃ antiferroelectric with a smeared phase transition differs in character from similar phenomena observed in relaxor ferroelectrics.     

Influence of the defect structure on the electrical conductivity of Pb5Ge3O11 single crystals at high temperatures

The impedance spectra of Pb₅Ge₃O₁₁ single crystals are measured in the frequency range from 5 Hz to 13 MHz at temperatures of 600 to 800 K in dry air and in a dry or wet nitrogen gas. It is found that the temperature and the gas composition significantly affect the electrical properties of the compound. The data obtained are used to discuss the origin of crystal lattice defects and their influence on charge transfer. It is concluded that the conduction is mixed in character (p-type electronic and ionic due to oxygen ions). The proton conduction is shown experimentally to be feasible. The possible mechanisms of proton transport in Pb₅Ge₃O₁₁ are discussed.     

Structural phase transitions of the B1–B2 type in small-sized ionic crystals

The features of structural phase transitions that occur under high pressure are studied. The density functional theory is used to calculate the B1–B2 phase transition pressure as a function of the crystal size for small-sized alkali halide crystals. A size effect (an increase in the phase transition pressure as the crystal grain radius decreases) is revealed for the B1–B2 transitions in all halogen compounds except for lithium fluoride, for which the dependence is inverse.     

Design of the cold atom PHARAO space clock and initial test results

In this paper we describe the cold atom clock PHARAO, designed for microgravity operation. All elements of the PHARAO engineering model have been manufactured and delivered to CNES, the French space agency. We present the clock design, its main characteristics, and initial science operation. PHARAO is one of the main components of the Atomic Clock Ensemble in Space payload that is scheduled to fly on board the International Space Station in 2010. PACS 07.87.+v; 06.30.Ft; 95.55.Sh; 32.80.Pj     

Synthesis and magnetic properties of multilayer Ni/Cu and NiFe/Cu nanowires

Highly ordered composite nanowires with multilayer Ni/Cu and NiFe/Cu have been fabricated by pulsed electrodeposition into nanoporous alumina membrane. The diameter of wires can be easily varied by pore size of alumina, ranging from 30 to 100 nm. The applied potential and the duration of each potential square pulse determine the thickness of the metal layers. The nanowires have been characterized by transmission electron microscopy (TEM), magnetic force microscopy (MFM), and vibrating sample magnetometer (VSM) measurements. The MFM images indicate that every ferromagnetic layer separated by Cu layer was present as single isolated domain-like magnet. This technique has potential use in the measurement and application of magnetic nanodevices.     

Noether analysis of zilch conservation laws and their generalization for the electromagnetic field. II. Use of poincaré-invariant formulation of the principle of least action

Uzhgorod Branch, Institute of Nuclear Research, Ukrainian SSR Academy of Sciences. Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 80, No. 3, pp. 340–352, September, 1989.     

System of cryostating wide-aperture nonlinear crystals for generating the fifth harmonic of neodymium-laser radiation

Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 51, No. 5, pp. 867–870, November, 1989.     

Electronically excited oxygen states in exoemission and heterogeneous catalytic oxidation reactions

The role played by electronically excited oxygen in exoemission and heterogeneous catalysis is considered. The results obtained in a study of thermally stimulated exoemission from the surface of Al₂O₃ and SiO₂ are compared with data of temperature-programmed desorption of singlet oxygen O₂(¹Δ_g) from the surface of Al₂O₃ and HZSM-5 zeolites with different SiO₂/Al₂O₃ ratios. The role played by electronically excited oxygen states in heterogeneous catalysis is discussed on the basis of our own and literature data. Thermally stimulated exoemission after the action of an electron flow is considered taking into account electron-stimulated desorption and the available data on electron bombardment in catalysis.     

A method for estimating the local lattice distortions near a magnetic ion from ligand hyperfine parameters: Yb3+trigonal centers in SrF2 and BaF2

An empirical relationship describing the radial dependence of the nondipole part of the anisotropic constant for the ligand hyperfine interaction in alkaline-earth fluorides is proposed. This relationship is used for calculating the distances between the magnetic ion and the fluorine ions involved in its nearest environment. The results of the calculations are in good agreement with the values obtained by other methods for both cubic and tetragonal fluorine centers in these crystals. The distances from the magnetic ion to different groups of nonequivalent fluorine ions of the nearest environment in Yb³⁺ trigonal centers of SrF₂ and BaF₂ are determined. It is found that the Yb³⁺ ion is slightly displaced along the trigonal axis away from the compensating fluorine ion.