Dipole and Quadrupole Skyrmions in S=1 (Pseudo)Spin Systems

In terms of spin coherent states we have investigated topological defects in 2D S=1 (pseudo)spin quantum system with the bilinear and biquadratic isotropic exchange in the continuum limit. The proper Hamiltonian of the model can be written as bilinear in the generators of SU(3) group (Gell-Mann matrices). The knowledge of such group structure allows us to obtain some new exact analytical results. Analysing the proper classical model we arrive at different skyrmionic solutions with finite energy and the spatial distribution of spin-dipole and/or spin-quadrupole moments termed as dipole, quadrupole, and dipole-quadrupole skyrmions, respectively. Among the latter we would like note the in-plane vortices with the in-plane distribution of spin moment, varying spin length, and the non-trivial distribution of spin-quadrupole moments.Comment: 20 pages, no figure

Large non-adiabatic hole polarons and matrix element effects in the angle-resolved photoemission spectroscopy of dielectric cuprates

It has been made an extention of the conventional theory based on the assumption of the well isolated Zhang-Rice singlet to be a first electron-removal state in dielectric copper oxide. One assumes the photohole has been localised on either small (pseudo)Jahn-Teller polaron or large non-adiabatic polaron enclosed one or four to five $CuO_4$ centers, respectively, with active one-center valent $(^{1}A_{1g}-{}^{1,3}E_{u})$ manifold. In the framework of the cluster model we have performed a model microscopic calculation of the ${\bf k}$-dependence of the matrix element effects and photon polarization effects for the angle-resolved photoemission in dielectric cuprate like $Sr_{2}CuO_{2}Cl_{2}$. We show that effects like the ''remnant Fermi surface'' detected in ARPES experiment for $Ca_{2}CuO_{2}Cl_{2}$ may be, in fact, a reflection of the matrix element effects, not a reflection of the original band-structure Fermi surface, or the strong antiferromagnetic correlations. The measured dispersion-like features in the low-energy part of the ARPES spectra may be a manifestation of the complex momentum-dependent spectral line-shape of the large PJT polaron response, not the dispersion of the well-isolated Zhang-Rice singlet in antiferromagnetic matrix.Comment: 16 pages, TeX, 9 eps figures adde

Microscopic mechanisms of spin-dependent electric polarization in 3d oxides

We present a short critical overview of different microscopic models for nonrelativistic and relativistic magnetoelectric coupling including the so-called "spin current scenario", ab-initio calculations, and several recent microscopic approaches to a spin-dependent electric polarization in 3d oxides.Comment: 8 pages, 3 figure

NMR and LDA evidence for spiral magnetic order in the chain cuprate LiCu2O2

We report on {6,7}Li nuclear magnetic resonance measurements of the spin-chain compound LiCu2O2 in the paramagnetic and magnetically ordered states. Below T about 24 K the NMR lineshape presents a clear signature of incommensurate (IC) static modulation of the local magnetic field consistent with an IC spiral modulation of the magnetic moments. {7}Li NMR reveals strong phason-like dynamical fluctuations extending well below 24 K. We hypothesize that a series of phase transitions at 24.2, 22.5, and 9 K reflects a "Devil's staircase" type behavior generic for IC systems. LDA based calculations of exchange integrals reveal a large in-chain frustration leading to a magnetical spiral.Comment: 4 pages, 4 figure

Interplay of p-d and d-d charge transfer transitions in rare-earth perovskite manganites

We have performed both theoretical and experimental study of optical response of parent perovskite manganites RMnO_3 with a main goal to elucidate nature of clearly visible optical features. Starting with a simple cluster model approach we addressed the both one-center (p-d) and two-center (d-d) charge transfer (CT) transitions, their polarization properties, the role played by structural parameters, orbital mixing, and spin degree of freedom. Optical complex dielectric function of single crystalline samples of RMnO_3 (R=La, Pr, Nd, Sm, Eu) was measured by ellipsometric technique at room temperature in the spectral range from 1.0 to 5.0 eV for two light polarizations: E \parallel c and E \perp c. The comparative analysis of the spectral behavior of \varepsilon _1 and \varepsilon _2 is believed to provide a more reliable assignment of spectral features. We have found an overall agreement between experimental spectra and theoretical predictions based on the theory of one-center p-d CT transitions and inter-site d-d CT transitions. Our experimental data and theoretical analysis evidence a dual nature of the dielectric gap in nominally stoichiometric matrix of perovskite manganites RMnO_3, it is formed by a superposition of forbidden or weak dipole allowed p-d CT transitions and inter-site d-d CT transitions. In fact, the parent perovskite manganites RMnO_3 should rather be sorted neither into the CT insulator nor the Mott-Hubbard insulator in the Zaanen, Sawatzky, Allen scheme.Comment: 20 pages, 6 figure

Dynamical charge inhomogeneity and crystal-field fluctuations for 4f ions in high-Tc cuprates

The main relaxation mechanism of crystal-field excitations in rare-earth ions in cuprates is believed to be provided by the fluctuations of crystalline electric field induced by a dynamic charge inhomogeneity generic for the doped cuprates. We address the generalized granular model as one of the model scenario for such an ingomogeneity where the cuprate charge subsystem remind that of Wigner crystal with the melting transition and phonon-like positional excitation modes. Formal description of R-ion relaxation coincides with that of recently suggested magnetoelastic mechanism.Comment: 4 page

ФЛУОРИМЕТРИЧЕСКОЕ ОПРЕДЕЛЕНИЕ ФЕНОЛА В ВОЗДУХЕ РАБОЧЕЙ ЗОНЫ С ХРОМАТОМЕМБРАННОЙ ЖИДКОСТНОЙ АБСОРБЦИЕЙ

This work is devoted to development scheme of continuous on-line control of the content of phenol in working area air using chromatomembrane liquid absorption and fluorimetric detection. Optimal rates of gas and liquid phases were determined and good convergence between continuous chromatomembrane liquid absorption variant of analysis and classic absorption into bubbler with chromatographic detection were shown. Completeness of absorption of phenol in a continuous chromatomembrane liquid absorption were determined not less than 98 %. Benefits of the developed scheme are simple automation, minimal time of operator parcipitation during analysis, no reagents using. It is possible to determine concentration of phenol in working area air in the range of 20 % of the maximum permissible concentration of up to 5 MPC with a frequency of 3-4 tests per hour.Keywords: chromatomembrane liquid absorption, automation of analysis, monitoring of the environment(Russian)DOI: http://dx.doi.org/10.15826/analitika.2013.17.4.016A. L. Moskvin, A. N. MelnichenkoFederal State Budgetary Educational Institution of Higher Professional Education «Saint Petersburg State University», Saint-Petersburg, Russian FederationРабота посвящена разработке схемы непрерывного on-line контроля содержания фенола в воздухе рабочей зоны с хроматомембранной жидкостной абсорбцией и флуориметрическим детектированием. Подобраны оптимальные для проведения измерений расходы жидкой и газовой фазы и показана хорошая сходимость результатов непрерывного варианта определения фенола в воздухе рабочей зоны с хроматомембранной жидкостной абсорбцией с классическим вариантом поглощения в барботёре с хроматографическим определением. Определена полнота поглощения фенола в условиях непрерывной абсорбции в хроматомембранной ячейке на уровне не менее 98 %. Преимуществами разработанной схемы являются: простота автоматизации, минимальное участие оператора, отсутствие необходимости использования реактивов. Возможно определение содержания фенола в воздухе рабочей зоны по предложенной схеме в диапазоне от 20 % от предельно допустимой концентрации до 5 ПДК с частотой 3-4 анализа в час.Ключевые слова: хроматомембранная жидкостная абсорбция, автоматизация анализа, контроль объектов окружающей средыDOI: http://dx.doi.org/10.15826/analitika.2013.17.4.01