Analysis of Ω<Subscript>c</Subscript><Superscript>*</Superscript>(css) and Ω<Subscript>b</Subscript><Superscript>*</Superscript>(bss) with QCD sum rules

In this article, we calculate the masses and residues of the heavy baryons Ω_c ^*(css) and Ω_b ^*(bss) with spin–parity with the QCD sum rules. The numerical values are compatible with the experimental data and other theoretical estimations. PACS 14.20.Lq, 14.20.Mr     

Phase formation in the BaCO<Subscript>3</Subscript>–PbO–Fe<Subscript>2</Subscript>O<Subscript>3</Subscript>–Nb<Subscript>2</Subscript>O<Subscript>5</Subscript> system

Features of the formation of lead-ferroniobate compounds in the xBaCO₃–(1 – x)PbO–Fe₂O₃–Nb₂O₅ system by solid-phase synthesis are investigated. For perovskite-type lead-ferroniobate solid solution, a single-phase concentration region is revealed at 1233 K. The crystalline structures of the synthesized compounds are refined using Rietveld analysis and the Pm3?m and R3m space groups. Ceramic samples of lead ferroniobate are studied by scanning electron microscopy.     

Large electrostrictive strain in lead-free Bi<Subscript>0.5</Subscript>Na<Subscript>0.5</Subscript>TiO<Subscript>3</Subscript>–BaTiO<Subscript>3</Subscript>–KNbO<Subscript>3</Subscript> ceramics

In the present work, (1−x)(0.935Bi_0.5Na_0.5TiO₃–0.065BaTiO₃)–xKNbO₃ (BNT–BT–KN, BNT–BT–100xKN) ceramics with x ranging from 0 to 0.1 were prepared by the conventional ceramic fabrication process. A large electrostrictive coefficient of ∼10⁻² m⁴ C⁻² is obtained with the composition x ranging from 0.02 to 0.1, which is close to the well-known electrostrictive material Pb(Mg_1/3Nb_2/3)O₃. Under an electric field of 4 kV/mm, the electrostrictive strain can reach as high as 0.08%. Besides, the electric field induced strain behavior indicates a temperature independent behavior within the temperature range of 20 to 150°C. The large electrostrictive strain is suggested to be ascribed to the formation of non-polar (NP) phase developed by the KNbO₃ substitution, and the high electrostrictive coefficient of BNT–BT–KN ceramics makes them great candidates to be applied in the new solid-state actuators.     

Electrical switching in the MoO<Subscript>3</Subscript>–WO<Subscript>3</Subscript>–P<Subscript>2</Subscript>O<Subscript>5</Subscript> and MoO<Subscript>3</Subscript>–P<Subscript>2</Subscript>O<Subscript>5</Subscript> glasses

High field electrical switching on blown films of MoO₃(60%)–P₂O₅(40%), MoO₃(50%)–WO₃(10%)–P₂O₅(40%), and MoO₃(45%)–WO₃(15%)–P₂O₅(40%) having different thicknesses was studied and compared. Switching was observed using two terminal samples. S-type current–voltage characteristic (current-controlled negative resistance—CCNR) with memory was observed in molybdenum–phosphate glasses, but N-type characteristic (voltage-controlled negative resistance—VCNR) with threshold in tungsten–molybdenum–phosphate glasses was observed. The important observation was that with the addition of WO₃ to binary MoO₃–P₂O5 led to a change of I–V characteristic from CCNR with memory to VCNR with threshold. The measurements of density and molar volume showed linear relation between MoO₃ content and density which decreased with the increase of MoO₃ content. The samples’ thickness had no significant effect on threshold voltage. The attained results also indicated that the electrode material had no effect on switching property of devices. The switching behavior of the devices did not show any dependence on the polarity of the applied voltage. In terms of the effect of heat on the switching behavior of molybdenum–phosphate glasses, it was found that threshold voltage decreases with increasing of temperature. Finally, the switching phenomenon was explained by thermal (formation of crystalline filaments) and electronic models.     

Structural and magnetoelectric properties of MFe<Subscript>2</Subscript>O<Subscript>4</Subscript>–PZT (M = Ni,Co) and La<Subscript>x</Subscript>(Ca,Sr)<Subscript>1-x</Subscript>MnO<Subscript>3</Subscript>–PZT multilayer composites

Thick-film layered magnetoelectric composites consisting of ferromagnetic and ferroelectric phases have been synthesized with nickel ferrite (NFO), cobalt ferrite, La_0.7Sr_0.3MnO₃ (LSMO), or La_0.7Ca_0.3MnO₃ (LCMO) and lead zirconate titanate (PZT). Structural, magnetic, and ferromagnetic resonance characterization shows evidence for defect-free ferrites, but deterioration of manganite parameters. The resistivity and dielectric constants are smaller than expected values. The magnetoelectric effect (ME) is stronger in ferrite–PZT than in manganite–PZT. The ME voltage coefficient _E at room temperature is the highest in NFO–PZT and the smallest for LCMO–PZT. The transverse ME effect is an order of magnitude stronger than the longitudinal effect. The magnitude of _E correlates well with magnetic permeability for the ferrites. PACS 75.80.+q; 75.70.Gg; 75.60.-d     

Magnetoinduced structural,Jahn–Teller,dielectric, and transport effects in La<Subscript>0.875</Subscript>Sr<Subscript>0.125</Subscript>MnO<Subscript>3</Subscript>

The temperature and magnetic field dependences of elastic moduli and resistance are studied in a La_0.875Sr_0.125MnO₃ single crystal. In addition to the metal–insulator transition, the structural transition from the cooperative J–T strongly distorted orthorhombic phase to the charge ordering phase is studied at T _J–T = 150 K in magnetic fields of up to 2 T. Results show it is possible to control the acoustic parameters in the vicinity of T _J–T via magnetic fields.     

Magnetic and magnetoresistive properties of Al<Subscript>2</Subscript>O<Subscript>3</Subscript>–Sr<Subscript>2</Subscript>FeMoO<Subscript>6–δ</Subscript>–Al<Subscript>2</Subscript>O<Subscript>3</Subscript> nanoheterostructures

A method has been developed for fabricating nanoporous matrices based on anodic aluminum oxide for the deposition of ferromagnetic nanoparticles in them. The modes of deposition of strontium ferromolybdate thin films prepared by the ion-plasma method have been worked out, and the magnetic and magnetoresistive properties, structure, and composition of the films have been investigated. It has been revealed that the microstructure and properties of the strontium ferromolybdate films deposited by ionplasma sputtering depend on the deposition rate and the temperature of the substrate. Based on the measurement of the electrical resistivity of nanoheterostructures in a magnetic field, it has been found that the magnetoresistance reaches 14% at T = 15 K and B = 8 T, which is due to the manifestation of tunneling magnetoresistance.     

Internal friction and magnetoelectric response in two-layer composites Tb<Subscript>0.12</Subscript>Dy<Subscript>0.2</Subscript>Fe<Subscript>0.68</Subscript>–PbZr<Subscript>0.53</Subscript>Ti<Subscript>0.47</Subscript>O<Subscript>3</Subscript>

The inverse magnetoelectric effect and internal friction in two-layer composites based on ferromagnetic Tb_0.12Dy_0.2Fe_0.68 and piezoelectric PbZr_0.53Ti_0.47O₃ are studied in an ac electrical field in the frequency range of 52–213 kHz at temperatures of 293 to 400 K. A correlation is found between the internal friction and the efficiency of the inverse magnetoelectric transformation at resonant frequencies.     

Elastic properties of TeO<Subscript>2</Subscript>–B<Subscript>2</Subscript>O<Subscript>3</Subscript>–Ag<Subscript>2</Subscript>O glasses

A series of glasses [(TeO₂) _x (B₂O₃)_1−x ]_1−y [Ag₂O] _y with x = 70 and y = 10, 15, 20, 25 and 30 mol% were synthesised by rapid quenching. Longitudinal and shear ultrasonic velocity were measured at room temperature and at 5 MHz frequency. Elastic properties, Poisson's ratio, microhardness, softening temperature and Debye temperature have been calculated from the measured density and ultrasonic velocity at room temperature. The experimental results indicate that the elastic constants depend upon the composition of the glasses and the role of the Ag₂O inside the glass network is discussed. Estimated parameters based on Makishima–Mackenzie theory and bond compression model were calculated in order to analyse the experimental elastic moduli. Comparison between the experimental elastic moduli data obtained in the study and the calculated theoretically by the mentioned above models has been discussed.     

Preparation and characterization of organic–inorganic hybrid compound [N(C<Subscript>4</Subscript>H<Subscript>9</Subscript>)<Subscript>4</Subscript>]<Subscript>2</Subscript>Cu<Subscript>2</Subscript>Cl<Subscript>6</Subscript>

Organic–inorganic hybrid sample [N(C₄H₉)₄]₂Cu₂Cl₆ was prepared via the reaction between copper chloride and tetrabutylammonium chloride. The compound was characterized by X-ray powder diffraction, IR, Raman, differential scanning calorimetry (DSC), DTA-TGA analysis and electrical impedance spectroscopy. DSC studies indicate a presence of one-phase transition at 343 K. The complex impedance of compound [N(C₄H₉)₄]₂Cu₂Cl₆ have been investigated in temperature and frequency ranges 300–380 K and 200 Hz–5 MHz, respectively. The Z′ and Z″ versus frequency plots are well fitted to an equivalent circuit model. The circuits consist of the parallel combination of bulk resistance R _p and constant phase elements CPE. The frequency dependence of the conductivity is interpreted in term of Jonscher's law: s(w) = s_dc + Awⁿ \sigma (\omega ){ } = {\sigma_{\rm{dc}}} + { }A{\omega^n} . The conductivity follows the Arrhenius relation. The variation of the value of these elements with temperatures confirmed the availability of the phase transition at 343 K detected by DSC and electrical measurements.     

Current dependent reorganization in superconducting Y<Subscript>1</Subscript>Ba<Subscript>2</Subscript>Cu<Subscript>3</Subscript>O<Subscript>7-δ</Subscript>

We present strong non-linear dynamic responses developing due to magnitude and type of driving current in bulk polycrystalline superconducting Y₁Ba₂Cu₃O_7-δ sample at zero magnetic field. Several novel types of dynamic changes induced by the transport current were observed via the time evolution of the voltage (V - t curves). The physical observations appearing in V - t curves were interpreted mainly with the reorganization of driving current in a multiply connected network of weak-link structure. It was found that such a dynamic process could cause an enhancement or suppression in superconducting order parameter due to the magnitude of the driving current and coupling strength of weak link structure together with the chemical and anisotropic states of the sample. It was shown that the general behavior of decays evolving in V - t curves is consistent with an exponential relation which is analogous to the glassy state relaxation.     

Current-induced voltage oscillations in superconducting Y<Subscript>1</Subscript>Ba<Subscript>2</Subscript>Cu<Subscript>3</Subscript>O<Subscript>7-δ</Subscript>

We investigated influence of bidirectional square wave current with long periods and dc current on the evolution of the voltage-time (V - t) curves in superconducting polycrystalline bulk Y₁Ba₂Cu₃O_7-δ (YBCO) material at the temperatures near the critical temperature. In a well-defined range of amplitudes and periods of driving current, and temperatures, novel type of non-linear dynamic responses was observed by means of the V-t curves. It was seen that such a non-linear response to bidirectional square wave current sometimes reflects itself as regular sinusoidal-like voltage oscillations. The sinusoidal-like and non-sinusoidal oscillations were discussed mainly in terms of the dynamic competition between pinning and depinning and significant relaxation effects which appear in this competing process. The density fluctuations associated with the current induced self-magnetic flux (SMF) lines and semi-elastic coupling of SMF lines with the pinning centers were also considered as possible physical mechanisms in the interpretation of the experimental results.     

Heat capacity of the [N(C<Subscript>2</Subscript>H<Subscript>5</Subscript>)<Subscript>4</Subscript>]<Subscript>2</Subscript>CdBr<Subscript>4</Subscript> crystal in the temperature range 80–300 K

The heat capacity of the [[N(C₂H₅)₄]₂CdBr₄ crystal is measured by the calorimetric method in the temperature range from 80 to 300 K. It is revealed for the first time that the temperature dependence of the heat capacity C _p (T) exhibits an anomaly associated with the first-order phase transition occurring at the temperature T ₁ = 226.5 K. A long relaxation of the temperature of the crystal is observed in the temperature range 150–165 K.     

Magnetorefractive effect in (Co<Subscript>50</Subscript>Fe<Subscript>50</Subscript>)<Subscript>x</Subscript>(Al<Subscript>2</Subscript>O<Subscript>3</Subscript>)<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript> granular films

The reflectivity spectra and the magnetorefractive effect (MRE) of (Co₅₀Fe₅₀)_x(Al₂O₃)_1?x metal-dielectric granular films (0.07<x<0.52) are analyzed in the IR spectral range λ=2.5–25 µm. It is revealed that the specific features observed in the spectra at λ≈8.5 and 20 µm are associated with the excitation of phonon modes in the dielectric matrix. The magnetorefractive effect in the films is observed below the percolation thresh-old only in p-polarized light and above the percolation threshold for both the p and s polarizations. It is demonstrated that the optical properties of (Co₅₀Fe₅₀)_x(Al₂O₃)_1?x films in the IR spectral range, to a first approximation, can be interpreted in the framework of the effective-medium theory and the magnetorefractive effect can be explained in terms of the modified Hagen-Rubens relation.     

Fractal magnetic microstructure in the (Co<Subscript>41</Subscript>Fe<Subscript>39</Subscript>B<Subscript>20</Subscript>)<Subscript>x</Subscript>(SiO<Subscript>2</Subscript>)<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript> nanocomposite films

Magnetostructural methods are applied to determine the exchange bond percolation limit in (Co₄₁Fe₃₉B₂₀)_x(SiO₂)_1?x nanocomposites (x _c = 0.30 ± 0.02), which separates the phase plane along the metal concentration axis into a superparamagnetic region and a ferromagnetic region. It is shown that, with respect to the singularities of the magnetization up to the magnetization saturation curves, the ferromagnetic region is further subdivided into three regions differing in the character of the spatial propagation of the magnetization ripples or in the magnetic correlation function characteristics. The fractal dimension of the nanocomposite magnetic microstructure near the percolation threshold is determined.     

Specific heat of the [NH<Subscript>2</Subscript>(CH<Subscript>3</Subscript>)<Subscript>2</Subscript>]<Subscript>2</Subscript>ZnCl<Subscript>4</Subscript> crystal in the temperature region 80–300 K

The specific heat of [NH₂(CH₃)₂]₂ZnCl₄ was measured calorimetrically in the temperature region 80–300 K. As the temperature T decreases, the C _p (T) dependence indicates a phase transition sequence, with the phase transition at T₆=151 K observed for the first time. The thermodynamic characteristics of the crystal were refined. The transformation occurring at T₂=298.3 K is shown to be an incommensurate-commensurate phase transition.     

Photoinduced phenomena in amorphous As<Subscript>4</Subscript>S<Subscript>3</Subscript>Se<Subscript>3</Subscript>–Sn films

We investigate the kinetics of photodarkening and recording of holographic diffraction gratings in amorphous As₄S₃Se₃ thin-film structures doped with tin (Sn) in concentrations of 0–10 at %. It is established that an increase in the Sn concentration leads to a decrease in the photodarkening rate and degree. The photodarkening kinetics is approximated by a stretched exponential function. It is found that an increase in the Sn concentration leads to a decrease in the transmission (photodarkening) variation in the investigated As₄S₃Se₃–Sn films. It is determined that, in the recording of holographic diffraction gratings at a Sn concentration of 3–8 at %, the As₄S₃Se₃–Sn films exhibit the maximum sensitivity and diffraction efficiency of the recorded gratings. It is shown that the dependence of diffraction efficiency on the As₄S₃Se₃ film thickness has the maximum at a film thickness of 4 µm.     

Characterization and transport properties of 10BaO–xAg<Subscript>2</Subscript>O–(85-x)V<Subscript>2</Subscript>O<Subscript>5</Subscript>–5TeO<Subscript>2</Subscript> glass system

Silver-based quaternary glasses were prepared by splat quenching technique. X-ray diffraction and differential scanning calorimetry were done for confirming their amorphous nature. The conductivity of the glasses was measured in the frequency range from 1 Hz to 32 MHz from room temperature to 373 K. Conductivity data, which obeys the Arrhenius type behavior, shows minimum at 30 mol% Ag₂O, suggesting that the conductivity mechanisms are different above and below these two regions. The minimum in conductivity is accompanied by an inverse behavior of activation energy. Experimental data suggests that a polaron hopping mechanism operates in the electronically conducting domain of 20 ≤ × ≤ 30, and an interstitial pair mechanism operates in the ionically conducting domain of 35 ≤ × ≤ 55.