Crystal fields in PrB6 and NdB6

The electron-phonon relaxation times of the crystal-field levels of the metastable state⁵D₄ of Tb³⁺ were measured between 2 and 4.2K. The relaxation of the lowest pseudodoublet (E=1.25 cm^–1) shows an Orbach process via higher crystal-field levels. The other levels show direct relaxation on a nanosecond time scale. The higher crystal-field levels were used to look for propagation of high-energy (4THz) nonequilibrium phonons by phonon-induced fluorescence. No ballistic propagation of high-energy phonons could be found.     

The special features of the ground state in CeAl3

The temperature (3–60 K) and transferred momentum (0.3–2.3 Å^?1) dependences of the intensity of quasi-elastic magnetic neutron scattering were studied for the polycrystalline heavy-fermion CeAl₃ compound to elucidate the special features of its ground state. Transferred momentum variations caused oscillations of the intensity of quasi-elastic magnetic neutron scattering, which was evidence of magnetic correlations in the f-electron subsystem occurring in a fairly wide temperature range.     

Specific features of the formation of defects in fullerene C46

The initial stage of the formation of defects in the fullerene C₄₆ has been investigated using the atomistic computer simulation. It has been found that the relatively low symmetry of this fullerene leads to the emergence of channels of defect formation, which have not been revealed in the fullerenes C₂₀, C₃₆, and C₆₀. These channels consist in breaking a single C-C bond (in contrast to the simultaneous breaking of two bonds in the course of the Stone-Wales transformation, which is characteristic of high-symmetry fullerenes). For some typical channels, the paths of transformation of the C₄₆ fullerene into the corresponding defect isomers have been determined and the heights of the potential barriers encountered in these paths have been calculated.     

Specific features of the ferroelectric state in two-layer barium strontium titanate-based heterostructures

The structural properties of one- and two-layer heterostructures based on the barium–strontium titanate of various compositions deposited by the Frank–Van der Merve on a magnesium oxide substrate have been studied. The heterostructures have been prepared by the rf sputtering of the stoichiometric ceramic targets in a Plazma 50 SE deposition system. The principal difference of this method of deposition from known analogs is that the growth of single-crystal films occurs from a disperse oxide phase formed in the plasma of a high-current rf discharge during the ceramic target sputtering at the cluster level. The peculiarities of the manifestation of the ferroelectric state in the two-layer heterostructures when changing the sequence order of the films with various compositions of barium–strontium titanate.     

Resonant coupling in the formation of ultracold ground state molecules via photoassociation

We demonstrate the existence of a new mechanism for the formation of ultracold molecules via photoassociation of cold cesium atoms. The experimental results, interpreted with numerical calculations, suggest that a resonant coupling between vibrational levels of the 0+u (6s+6p1/2) and (6s+6p3/2) states enables formation of ultracold molecules in vibrational levels of the ground state well below the 6s+6s dissociation limit. Such a scheme should be observable with many other electronic states and atomic species.     

Specific features of the formation of diffraction patterns of metallofullerene crystals

The specific features of the formation of diffraction patterns of face-centered cubic crystals of metallofullerene clathrates have been investigated. It has been demonstrated that the presence of dopants in holes of fullerite crystals substantially affects the ratio between the X-ray reflection intensities. The regularities in the redistribution of the intensities of diffraction peaks when metal atoms fill interstices and intramolecular cavities of the face-centered cubic fullerite crystal have been established.     

PrB6电子结构及光学性能的第一性原理研究

本文采用基于第一性原理的密度泛函理论(DFT)赝势平面波方法,系统研究了稀土PrB6的电子结构、自旋极化态密度和光学性质,并在此基础上预测了PrB6薄膜的太阳辐射屏蔽性能。研究发现：PrB6属于金属导体材料,其费米面附近的能带主要由B的2p和Pr的4f层的电子态构成;PrB6对近红外辐射具有较高的反射率和较强的吸收;PrB6薄膜的理论透过率曲线在可见光区呈“吊铃”型分布,其不仅具有较好的可见光透过率而且对紫外和近红外辐射具有较强的屏蔽性能。此研究结果将为PrB6光电材料的设计和应用提供理论依据。     

PrB6电子结构及光学性能的第一性原理研究

本文采用基于第一性原理的密度泛函理论(DFT)赝势平面波方法,系统研究了稀土PrB6的电子结构、自旋极化态密度和光学性质,并在此基础上预测了PrB6薄膜的太阳辐射屏蔽性能。研究发现：PrB6属于金属导体材料,其费米面附近的能带主要由B的2p和Pr的4f层的电子态构成;PrB6对近红外辐射具有较高的反射率和较强的吸收;PrB6薄膜的理论透过率曲线在可见光区呈“吊铃”型分布,其不仅具有较好的可见光透过率而且对紫外和近红外辐射具有较强的屏蔽性能。此研究结果将为PrB6光电材料的设计和应用提供理论依据。     

Specific features of the electrical conductivity of V6O11

A study has been made of the electrical conductivity of V₆O₁₁ single crystals over a broad range of temperatures covering the regions of the metal phase, metal-insulator phase transition, and insulator phase. It has been shown that the electrical conductivity of the metal phase correlates with the Mott limit of minimum conductivity. To explain the temperature dependence of the electrical conductivity of the V₆O₁₁ insulator phase, the theory of hopping conduction taking into account the effect of thermal vibration of atoms on the resonance integral has been invoked.     

Specific features of the formation of the ferroelectric phase in polytypes of TlGaSe2 crystals

The polytypism of layered crystals of thallium gallium diselenide TlGaSe₂ has been found to substantially affect the temperature of phase transformations and the mechanism of formation of the polar state in these ferroelectrics. In particular, it is shown that the phase transition observed in the C-TlGaSe₂ polytype is an improper ferroelectric phase transition occurring at a temperature T _c ≈ 108 K, whereas the phase transition observed in the 2C-TlGaSe₂ polytype is a proper ferroelectric phase transition occurring at a higher temperature T _c ≈ 111 K. It is concluded that the elucidation of the polytype of a particular sample is a necessary stage of investigation of the TlGaSe₂ crystals.     

Specific features of magnetic structure formation in orbitally degenerate BiMnO3 manganite

The orbital structure and magnetic ordering of the Jahn-Teller multiferroic BiMnO₃ manganite have been theoretically studied. It is shown that the orbital structure depends not only on the nearest-neighbor oxygen environment of manganese ions, but also on their next-to-nearest neighbors. The orbital structure significantly influences the magnetic order that forms as a result of competition between ferromagnetic and antiferromagnetic exchange interactions.     

Specific features of the effect of dopants on the phase formation of YBO3 and ScBO3 during synthesis from the amorphous precursor state

The effect of dopants on the structural states of the YBO₃ and ScBO₃ borates during sequential isothermal annealings of the amorphous precursor state and the batch from a mixture of micropowders of initial rare-earth metal oxides of the same composition has been investigated using X-ray diffraction. It has been demonstrated that, in both cases, the phase sequences of rare-earth metal borates differ substantially from each other. Possible factors responsible for the strong effect of dopants on the structural sequences during the synthesis of the YBO₃ and ScBO₃ borates from the amorphous precursor state have been analyzed.     

Specific features of the formation of vanadium oxide micro- and nanocrystals during gas-phase synthesis

A modified method of gas-phase synthesis of vanadium oxide micro- and nanocrystals was developed. The morphology of the crystals obtained and its dependence on the synthesis conditions are analyzed. The method is shown to permit the growth of rod-shaped crystals rectangular in cross section, whiskers, crystals with a rectangular cavity, and also lamellar crystals and planar ordered textures consisting of oriented rodshaped crystals. The microcrystals synthesized were used to study the mutual reversible transformation of various vanadium oxides using oxidation and reduction reactions.     

Specific features of the generation of aqueous solutions of Rhodamine 6G in laser pumping

M. V. Lomonosov Moscow State University, Vorob'yovy Gory, Moscow, 119899, Russia. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 63, No. 2, pp. 236–241, March–April, 1996.     

On the ground state of the Kondo lattice system CeCu6

Magnetization measurements have been performed on a single crystal of CeCu₆ along the three main crystallographic directions between 1.5 and 300 K. The results are interpreted in terms of a crystal field calculation slightly modified by a spin fluctuation contribution of Kondo origin. Anisotropic magnetic properties of the Kondo lattice are discussed.     

Specific features of the formation of phase states in a non-Heisenberg magnet with S = 2

Spin states of a non-Heisenberg magnet with a magnetic ion spin of 2 have been determined. It has been shown that the inclusion of the higher-order spin invariants leads to realization of specific phases with the tensor order parameters whose realization is impossible in magnets with S = 1. The free energy of the system in different spin states has been studied. The geometric images of the tensor phases in the spin space have been determined.     

Specific features of the formation of oxygen defects in the SrFeO2.5 ferrate with a brownmillerite structure

The electronic structure and chemical bonding in the Sr₂Fe₂O₅ strontium ferrate are investigated in the framework of the ab initio linear-muffin-tin-orbital tight-binding representation and extended Hükcel calculations. Models of defect formation (oxygen vacancies and anti-Frenkel defects) in the brownmillerite structure are considered. A model of ion transfer in strontium ferrate is proposed reasoning from the results of the calculations.     

Identification of the Li ground state

The proton-stripping reaction from a ¹¹Be radioactive beam incident on a beryllium target demonstrates that only (7±3)% of the ⁹Li residues in the reaction are in coincidence with the 2.7 MeV γ-ray corresponding to the ⁹Li first excited state. This implies that the previously observed low-energy neutrons from the decay of the unbound nucleus ¹⁰Li represent a direct l=0 transition to the ⁹Li ground state. Consequently, neutron-unbound ¹⁰Li is proven to have the same parity inversion as occurs in the case of ¹¹Be with a  intruder state below the natural parity state.