Optical properties of the HfO2 ? x N x and TiO2 ? x N x films prepared by ion beam sputtering

Optical characteristics of the HfO_{2 − x} N _x and TiO_{2 − x} N _x films obtained by reactive ion beam sputtering have been investigated by spectral ellipsometry. The chemical composition of the films was determined using X-ray photoelectron spectroscopy. The nitrogen content in the oxynitride films (determined by the N₂/O₂ ratio in the gas mixture during synthesis) reached ≈9 at % for TiO_{2 − x} N _x and ≈ 6 at % for HfO_{2 − x} N _x . It is found that the dispersion relations n(λ) and k(λ) for the TiO_{2 − x} N _x films change from those characteristic of titanium dioxide to those typical of titanium nitride with an increase in the nitrogen content from 0 to ≈9 at %. The optical parameters of the HfO_{2 − x} N _x films depend weakly on the nitrogen content in the range 0–6 at %. Original Russian Text ? V.V. Atuchin, V.N. Kruchinin, A.V. Kalinkin, V.Sh. Aliev, S.V. Rykhlitskiĭ, V.A. Shvets, E.V. Spesivtsev, 2009, published in Optika i Spektroskopiya, 2009, Vol. 106, No. 1, pp. 77–82.     

119Sn and 57Fe M?ssbauer study of the local structure of perovskite-type ferrites CaFe2 ? x N x O5 ( N = Sc, Al) and manganite CaMn7O12

Anion-deficient substituted ferrites Ca₂Fe_{2 − x} N _x O₅ (N = Sc³⁺, Al³⁺) and mixed manganite CaMn₇O₁₂ have been investigated by ¹¹⁹Sn and ⁵⁷Fe probe M?ssbauer spectroscopy. The mechanism of charge compensation for heterovalent impurity Sn⁴⁺ ions in the structure of the ferrite Ca₂Fe₂O₅ has been established. The presence of nonequivalent crystallographic positions of manganese cations, caused by their charge ordering in the structure of the manganite CaMn₇O₁₂, is shown. Magnetic ordering of Mn³⁺ and Mn⁴⁺ cations in the octahedral sublattice of CaMn₇O₁₂ at T < T _M2 ≈ 90 K is established. Original Russian Text ? A.V. Sobolev, I.A. Presnyakov, K.V. Pokholok, V.S. Rusakov, T.V. Gubaidulina, A.V. Baranov, G. Demazeau, 2007, published in Izvestiya Rossiiskoi Akademii Nauk Seriya Fizicheskaya, 2007, Vol. 71, No. 9, pp. 1347–1354.     

Effect of copper doping on charge ordering in La1/3Ca2/3Mn1 ? y Cu y O3 (0 ≤ y ≤ 0.07)

The effect of copper doping on charge-orbital ordering in La_1/3Ca_2/3Mn_{1 − y} Cu _y O₃ (0 ≤ y ≤ 0.07) is studied by measuring the temperature dependences of the magnetization, the electrical resistivity, and the heat capacity in combination with an electron microscopic investigation of the structure. It is demonstrated that copper doping leads to a lowering of the charge ordering temperature T _CO and that this decrease is proportional to the decrease in the Mn³⁺ ion concentration. In the temperature range 5–300 K, the semiconducting pattern of the electrical resistivity persists for all values of 0 ≤ y ≤ 0.07. Electron microscope studies have shown that the presence of copper suppresses the formation of a regular superstructure, which is characteristic of the undoped starting compound, beginning already from low concentrations (y = 0.01). Differential scanning calorimetry revealed a substantial decrease in the transition entropy at the onset of charge ordering in copper-doped samples as compared to the starting compound. Doping with copper destroys long-range charge-orbital ordering and retains apparently only short-range order. Original Russian Text ? T.S. Orlova, J.Y. Laval, Ph. Monod, V.S. Zakhvalinskiĭ, V.M. Egorov, Yu.P. Stepanov, 2009, published in Fizika Tverdogo Tela, 2009, Vol. 51, No. 1, pp. 91–97.     

Charge ordering in crystals of Pr1? x Sr x MnO3 ( x = 0.22, 0.24) ferromagnetic manganites

The structural and magnetic states of Pr_1−x Sr _x MnO₃ (x = 0.22, 0.24) manganite crystals were studied over a wide temperature range. Measurements of the magnetic susceptibility and electrical resistivity demonstrated that these manganites belong to the class of ferromagnetic semiconductors. Thermal neutron elastic scattering patterns revealed that, in the temperature range 4.2–350 K, the manganites have an orthorhombic structure (space group Pnma) with a well-pronounced cooperative Jahn-Teller effect. Major emphasis was placed on the nuclear magnetic superstructure with a wave vector q = (2π/2a, 0, 2π/2c). It was shown that this superstructure suggests 1/4-type charge ordering in the manganites under investigation. Original Russian Text ? S.F. Dubinin, S.G. Teploukhov, V.E. Arkhipov, V.D. Parkhomenko, é.A. Neĭfel’d, A.V. Korolev, N.A. Ugryumova, Ya.M. Mukovskiĭ, 2007, published in Fizika Tverdogo Tela, 2007, Vol. 49, No. 4, pp. 704–710.     

Magnetic transformations in the Sr0.78Y0.22Co1 ? xFexO3 ? γ system with a perovskite structure

The Sr_0.78Y_0.22Co_{1 − x} Fe _x O_{3 − γ} cobaltite system is studied by neutron and X-ray diffraction and by measuring the magnetization and elastic properties. The crystal structure of the composition with x = 0 is described in terms of the monoclinic space group A2/m with the unit cell 2 a _p × 4a _p × 2 a _p , and the crystal structure of the composition with x = 0.12 is orthorhombic (space group Imma). The crystal structure of these compounds is characterized by alternating CoO₆ and CoO_4.5 layers. The magnetic structure is a G-type antiferromagnetic structure. The magnetic moments in the CoO₆ layers are significantly higher than those in the CoO_4.5 layers. In the compound with x = 0, magnetic measurements reveal a small ferromagnetic component (0.2 μ_B/Co) below T _N ≈ 350 K. Near T _N, a phase transformation occurs and lowers the crystallographic symmetry. Doping with iron ions suppresses the ferromagnetic component and sharply increases the average magnetic moments in both layers. The spontaneous magnetization is assumed to result from noncollinear magnetic moments, which can be caused by the competition of exchange interactions of different signs and magnetic anisotropy. The compounds with x = 0.5 and 1.0 are cubic (space group Pm3m) and are characterized by a G-type collinear antiferromagnetic structure. Original Russian Text ? I.O. Troyanchuk, D.V. Karpinsky, V.M. Dobryanskiĭ, A.N. Chobot, G.M. Chobot, A.P. Sazonov, 2009, published in Zhurnal éksperimental’noĭ i Teoreticheskoĭ Fiziki, 2009, Vol. 135, No. 3, pp. 490–497.     

Modeling of the effect of low intensity ionizing radiation on MOS elements of VLSI circuits

A method for predicting the tolerance of MOS VLSI circuits to low intensity cosmic rays is reported. The method is based on the analysis of the test MOS structure response to high-dose-rate radiation and on the solution of the system of equations describing the radiation-charge accumulation in the gate oxide of the poly-Si-SiO₂(P)-Si structure and its relaxation by tunneling and thermal emission. Original Russian Text ? M.N. Levin, E.V. Bondarenko, A.V. Tatarintsev, V.R. Gitlin, V.A. Makarenko, 2009, published in Izvestiya Rossiiskoi Akademii Nauk. Seriya Fizicheskaya, 2009, Vol. 73, No. 2, pp. 264–267.     

Magnetic, electrical, and optical properties of Ca1 ? x Ce x MnO3 ( x ≤ 0.12) single crystals

The magnetic, electrical, and optical properties of Ca_{1 − x} Ce _x MnO₃ (x≤0.12) manganite single crystals are investigated with the aim of revealing the specific features of the multiphase electronic and magnetic state as a function of the cerium concentration and the atmosphere used for growing single crystals. It is found that the concentration dependence of the low-temperature magnetization M(x) of the single crystals is shifted toward the high-concentration range as compared to the corresponding dependence of the polycrystals, which is explained by the predominant cation deficiency. The electrical resistivity and the reflection spectra of the single crystals in the infrared spectral range indicate that charge carriers exhibit a band nature at temperatures close to room temperature. The temperature dependence of the electrical resistivity of the single crystal with x = 0.08, which has the maximum magnetization in the studied series of Ca_{1 − x} Ce _x MnO₃ compounds, unlike polycrystals, exhibits a metallic behavior over the entire temperature range. The G-type antiferromagnetic phase with the Néel and Curie temperatures T _N(G) = T _C = 100 K is characterized by maxima of the electrical resistivity ρ and the magnetoresistance Δρ/ρ = |(ρ₀ − ρ _H )/ρ₀| = 38% in the magnetic field H = 90 kOe. The magnetoresistance Δρ/ρ of the single crystals at cerium concentrations x = 0.10 and 0.12 with variations in temperature exhibit three specific features: near the temperature of charge ordering T _co, near the temperature of the magnetic phase transition to the C-type antiferromagnetic phase T _N(C), and near the temperature of the phase transition to the magnetic charge-ordered phase T _N(MCO). An anomalous temperature dependence of the magnetization is revealed for a single crystal with x = 0.10 grown in oxygen at a pressure of 5 atm, which is explained by the presence of regions with hole conductivity due to cation deficiency. The inhomogeneous electronic and magnetic state is associated with the interrelation of the charge, orbital, and spin orderings. Original Russian Text ? N.N. Loshkareva, A.V. Korolev, N.I. Solin, E.V. Mostovshchikova, S.V. Naumov, N.V. Kostromitina, A.M. Balbashov, 2009, published in Zhurnal éksperimental’noĭ i Teoreticheskoĭ Fiziki, 2009, Vol. 135, No. 1, pp. 98–107.     

Model-independent Breit-Wigner parameters of S 11(1535) and S 11 (1650) nucleon resonances from experimental data on η meson photoproduction on protons

The results of phenomenological partial-wave analysis of angular distributions for the process γp → νp measured at the Tohoku University (Japan) and model-independent estimates of Breit-Wigner parameters of S ₁₁(1535) and S ₁₁(1650) nucleon resonances obtained based on these data are presented. Original Russian Text ? E.V. Balandina, E.M. Leikin, N.P. Yudin, 2009, published in Vestnik Moskovskogo Universiteta. Fizika, 2009, No. 1, pp. 87–89.     

On the dimensionality of superconductivity in cuprate superconductors

The question of the dimensionality of superconductivity is considered within the framework of a model of superconductivity via asymmetric, delocalized “crystalline” π orbitals (analogous to the corresponding molecular orbitals) extending along chains of covalently bonded copper and oxygen ions. It is shown that superconductivity is preceded by a separation of the bonds in the CuO₂ layer into covalent and ionic bonds with ordering of the covalent bonds into chains. Such an ordering facilitates the formation of a crystalline π orbital lowering the crystal energy by the resonance energy of the π bond and is therefore favored. The superconducting current is created by non-dissipative motion of π-electron pairs along the asymmetric, “crystalline” π orbitals extending along chains of covalently bonded copper and oxygen ions, in the presence of an ionic bond between neighboring chains extending through the easily polarizable O²⁻ ions. This ionic bond correlates the motion of the electron pairs along all the π orbitals and stabilizes the superconducting state. Only in this sense is the apparent “onedimensionality” of superconductivity in cuprate superconductors to be understood. Zh. Tekh. Fiz. 68, 82–84 (November 1998)     

Measurement of the e+e? → π+π? cross section with the CMD-2 detector in the 370–520-MeV energy range

The results of the experiment on the measurement of the e ⁺ e ⁻ → π⁺π⁻ cross section in a cm energy range of 370–520 MeV are presented. The systematic measurement error is equal to 0.7%. In the vector dominance model, the pion electromagnetic radius is calculated using all the CMD-2 data on the pion form factor. The cross section for the production of a muon pair is measured in the energy range of the experiment. Original Russian Text ? V.M. Aul’chenko, R.R. Akhmetshin, V.Sh. Banzarov, L.M. Barkov, N.S. Bashtovoĭ, D.V. Bondarev, A.E. Bondar’, A.V. Bragin, N.I. Gabyshev, D.A. Gorbachev, A.A. Grebenyuk, D.N. Grigor’ev, S.K. Dhawan, D.A. Epifanov, A.S. Zaĭtsev, S.G. Zverev, F.V. Ignatov, V.F. Kazanin, S.V. Karpov, I.A. Koop, P.P. Krokovny, A.S. Kuz’min, I.B. Logashenko, P.A. Lukin, A.P. Lysenko, A.I. Mil’shteĭn, K.Yu. Mikhaĭlov, I.N. Nesterenko, M.A. Nikulin, A.V. Otboev, V.S. Okhapkin, E.A. Perevedentsev, A.S. Popov, S.I. Redin, B.L. Roberts, N.I. Root, A.A. Ruban, N.M. Ryskulov, A.L. Sibidanov, V.A. Sidorov, A.N. Skrinsky, V.P. Smakhtin, I.G. Snopkov, E.P. Solodov, J.A. Thompson, G.V. Fedotovich, B.I. Khazin, V.W. Hughes, A.G. Shamov, Yu.M. Shatunov, B.A. Shvarts, S.I. éĭdel’man, Yu.V. Yudin, 2006, published in Pis’ma v Zhurnal éksperimental’noĭ i Teoreticheskoĭ Fiziki, 2006, Vol. 84, No. 8, pp. 491–495.     

Study of the nd-breakup reaction in the kinematical region of the nn final-state interaction

The neutron neutron (nn) final-state interaction has been studied in the n + d → p + n + n reaction at 40 ± 5 MeV. Data on the dependence of reaction yield on the relative energy of two neutrons emitted in a narrow cone of angles are obtained. The value of the nn-scattering length deduced from a comparison of the shape of FSI peak with simulation data is a _nn = −17.9 ± 1.0 fm, where the error indicates the statistical uncertainty. Original Russian Text ? S.V. Zuyev, E.S. Konobeevski, M.V. Mordovskoy, S.I. Potashev, 2009, published in Izvestiya Rossiiskoi Akademii Nauk. Seriya Fizicheskaya, 2009, Vol. 73, No. 6, pp. 843–845.     

Imperfection of the nanostructure, phase transitions, 55Mn NMR, and magnetoresistive properties of La 0.73+ Ca 0.3 ? x2+ Sr x2+ MnO3 ± δ ceramics

Magnetoresistive ceramic samples La_0.7Ca_{0.3 − x} Sr _x MnO_{3 ± δ} sintered at temperatures of 1150 and 1350°C are investigated using X-ray diffraction, microscopic, resistance, and magnetic (χ, ⁵⁵Mn NMR) measurements. The specific features of the influence of the composition on the type and parameters of the perovskite structure, its imperfection, the porous crystallite structure, the metal-semiconductor and ferromagnetic-paramagnetic phase transitions, the ⁵⁵Mn NMR spectra, and the magnetoresistance effect are established. The magnetic phase diagram is constructed. The conclusions are drawn regarding the nonuniformity of the distribution of ions and vacancies around manganese involved in the high-frequency electron-hole exchange (Mn³⁺ ai Mn⁴⁺) and the nanostructured separation of the perovskite structure containing anion and cation vacancies, with the concentrations and magnetoresistance effect decreasing and the lattice parameters and phase transition temperatures increasing as calcium is replaced by strontium. Original Russian Text ? A.V. Pashchenko, A.A. Shemyakov, V.P. Pashchenko, V.A. Turchenko, V.K. Prokopenko, Yu.F. Revenko, Yu.V. Medvedev, B.M. éfros, G.G. Levchenko, 2009, published in Fizika Tverdogo Tela, 2009, Vol. 51, No. 6, pp. 1127–1136.     

New nuclear charge radii database

Several large relational databases (DBs) containing various atomic nucleus parameters and nuclear reaction features were produced at the Centre for Photonuclear Experiments Data (Centr Dannyh Fotoyadernykh Eksperimentov (CDFE)) of the Skobeltsyn Institute of Nuclear Physics, Moscow State University). The sources are numerical data founds maintained by International Nuclear Data Centers Network of the International Atomic Energy Agency (IAEA) and produced by CDFE. The original CDFE product is the electronic “Chart of Quadrupole Nuclear Deformations” which includes ∼2000 sets of data on nuclei quadrupole moments Q and quadrupole deformation parameters β₂ for ∼1500 nuclei. At last time, in the frame of joint research with the Joint Institute for Nuclear Research (JINR) that electronic Chart was supplemented with the data on nuclear mean-root-square (MRS) charge radii (∼900 isotopes of 90 elements (Z = 1–96, N = 0–152)) and therefore transformed into the “Chart of Nucleus Shape and Size Parameters”—complete collection of data under discussion. New Chart allows one to investigate the isotopic and isotonic behavior of nuclei quadrupole moments, parameters of quadrupole deformation and charge radii, and study the R(Z, N) surface structure and R(A) dependence of the fine structure. Original Russian Text ? I.N. Boboshin, V.V. Varlamov, Yu.P. Gangrsky, B.S. Ishkhanov, S.Yu. Komarov, K.P. Marinova, 2009, published in Izvestiya Rossiiskoi Akademii Nauk. Seriya Fizicheskaya, 2009, Vol. 73, No. 6, pp. 857–862.     

Low-field magnetization of ludwigites Co3O2BO3 and Co3 ? xFexO2BO3 (x ≈ 0.14)

Ludwigite single crystals of compositions Co₃O₂BO₃ and Co_{3 − x} Fe _x O₂BO₃ (x ≈ 0.14) have been synthesized. The crystal structure is investigated at room temperature, and the magnetization is studied in the temperature range T = 4.2–100 K in magnetic fields of up to 600 Oe. The orthorhombic symmetry is revealed, and the unit cell parameters are determined. A number of features are established for the temperature dependence of the magnetization. In unsubstituted Co₃O₂BO₃, two magnetic transitions are found at T _C1 = 43 K and T _C2 = 15 K. At temperatures below 40 K, spin-glass state is revealed. Substitution of iron ions for cobalt ions leads to a noticeable shift in the magnetic transitions toward the high-temperature range: T _C1 = 83 K and T _C2 = 74 K. A ferromagnetic ordering of the P type is found in the Co_{3 − x} Fe _x O₂BO₃ (x ≈ 0.14) compound. Original Russian Text ? N.V. Kazak, N.B. Ivanova, V.V. Rudenko, A.D. Vasil’ev, D.A. Velikanov, S.G. Ovchinnikov, 2009, published in Fizika Tverdogo Tela, 2009, Vol. 51, No. 5, pp. 916–919.     

Functionalized perylenes: origin of the enhanced electrical performances

In this letter we compare the transistor performances of two solution-processed perylene derivatives: N,N′-bis (n-octyl)- dicyanoperylene-3,4:9,10-bis(dicarboximide) (PDI8-CN₂) and N,N′-1H,1H-perfluorobutyl dicyanoperylenediimide (PDIF-CN₂). Perylenediimide nitrogen functionalization with perfluoroalkyl vs. alkyl chains improves the electron mobility of solution-processed organic field effect transistors (OFETs) by one order of magnitude. Time resolved spectroscopy allows attributing this increment to a higher degree of co-facial arrangement of the fluorinated molecules. This supramolecular arrangement enhances the π–π overlap leading to more efficient electron transport.     

Single-particle levels of nuclei in the vicinity of the doubly magic nuclei 2048 Ca28 and 2856 Ni28

Isotonic and isotopic dependences of single-particle energies of neutron and proton states in 20 ≤ Z ≤ 28 and 24 ≤ N ≤ 32 nuclei are investigated, these energies being determined by matching data on nucleon-stripping and nucleon-pickup reactions on the same nucleus. Regularities of the formation of the spectra of single-particle levels in Z, N = 20, 28 magic nuclei are demonstrated. A distinctive feature is found in the isotonic dependence of the energy of the 1 f _5/2 neutron level, this feature being consistent with the assumption that j _>-j _< interaction is operative in nuclei. The single-particle energies calculated by using the potential of the dispersive optical model are found to be consistent with experimental data within their errors. Original Russian Text ? O.V. Bespalova, I.N. Boboshin, V.V. Varlamov, T.A. Ermakova, B.S. Ishkhanov, E.A. Romanovsky, T.I. Spasskaya, T.P. Timokhina, 2008, published in Yadernaya Fizika, 2008, Vol. 71, No. 1, pp. 37–49.     

Dimensional Crossover of Magnetic Transition in Diluted Ising Spin Nets Probed by Muon Spin Relaxation

The magnetic ordering process of Ising spins on diluted square lattice was studied by muon spin relaxation using model compounds Rb₂Co _c Mg_1−c F₄. Muon relaxation shows an anomaly at a remarkably higher temperature T _N ^μSR than the transition temperature determined by neutron Bragg scattering T _N ^ND near the percolation threshold for square lattice (c _p=0.593). The difference between the two temperatures amounts to 50% of T _N ^ND just above c _p. The field cooling effect of DC magnetic susceptibility is appreciable below T _N ^ND while the temperature of the anomaly in AC susceptibility approaches to T _N ^μSR as the frequency is increased. It was concluded that there is a crossover from two-dimensional ordering at T _N ^μSR to three-dimensional ordering at T _N ^ND but the two-dimensional order between T _N ^μSR and T _N ^ND has slow fluctuations due to the fractal structure with a plenty of weak links. This revised version was published online in September 2006 with corrections to the Cover Date.     

Confrontation of nucleus deformation and multipole mixture parameters in (2+0 n ?2+01) transitions with rotational band structure for K π = 0 2+ and 0 3+

The difference of the energies of levels Δ _n = E _lev(2⁺0 _n ) − E _lev(0⁺0 _n ) at n = 1, 2, and 3 and the multipole-mixture parameter δ for (2⁺0₂−2⁺0₁) and (2⁺0₃−2⁺0₁) transitions are contrasted against the structure of the K ^π = 0₂⁺ and 0₃⁺ rotational bands that was calculated on the basis of the quasiparticle-phonon model. The values of (Δ₂ − Δ₁), (Δ₃ − Δ₁), and (Δ₂ − Δ₃) are found to correlate with the sign of the parameter δ and with the calculated structure of the K ^π = 0₂⁺ and 0₃⁺ bands. Original Russian Text ? A.M. Demidov, L.I. Govor, V.A. Kurkin, I.V. Mikhailov, 2009, published in Yadernaya Fizika, 2009, Vol. 72, No. 2, pp. 236–240.     

Influence of defects in a silicon dioxide thin layer on the processes of silicidation in the Fe/SiO2/Si(001) system

The kinetics of the evolution of the structure and phase composition of the Fe/SiO₂/Si(001) system under different conditions for deposition of the iron layer and subsequent annealing is considered. It is established that the SiO₂ thin layer (∼1 nm) is not destroyed during iron deposition over a wide temperature range from 20 to 650°C. As a result, iron films with different morphologies are formed on the surface of the oxide. Annealing leads to the destruction of the SiO₂ layer at defect sites. This brings about the interaction of iron atoms with the silicon substrate and subsequent formation of iron silicides. Original Russian Text ? V.V. Balashev, V.V. Korobtsov, T.A. Pisarenko, E.A. Chusovitin, 2009, published in Fizika Tverdogo Tela, 2009, Vol. 51, No. 3, pp. 565–571.     

Activity study of graphite from the chernobyl NPP reactor

The content of the isotopes ³H, ¹⁴C, ³⁶Cl, ⁵⁵Fe, ⁵⁹Ni, ⁶³Ni, ⁶⁰Co, ⁹⁰Sr, ^93m Nb, ¹⁰⁸Ag, ¹³³Ba, ¹³⁴Cs, ¹³⁷Cs, ¹⁵⁴Eu, and ¹⁵⁵Eu in the GRP-2-125 graphite from the reactor of Power Unit 2 at the Chernobyl Nuclear Power Plant was measured. The results were compared with the calculations and literature data. Some regularities and correlations were revealed in the content of various radionuclides in graphite. Graphite porosity and desorption of radionuclides from graphite were studied. Original Russian Text ? M.D. Bondar’kov, D.M. Bondar’kov, A.M. Maksimenko, V.A. Zheltonozhskii, M.V. Zheltonozhskaya, V.V. Petrov, A.I. Savin, 2009, published in Izvestiya Rossiiskoi Akademii Nauk. Seriya Fizicheskaya, 2009, Vol. 73, No. 2, pp. 274–278.