Metastable states and physical characteristics of a subsystem of interstitial impurities

The behavior of mobile interstitial impurities in a crystal matrix has been simulated numerically. The contribution of the impurity subsystem to the heat capacity, and the effect of clusterization on the temperature dependence of the impurity diffusion coefficient have been studied. Fiz. Tverd. Tela (St. Petersburg) 40, 475–480 (March 1998)     

The influence of magnetic and structural heterogeneity on thermopower,magnetothermopower, electrical resistivity,and magnetoresistivity of Nd<Subscript>0.5</Subscript>Sr<Subscript>0.5</Subscript>MnO<Subscript>3</Subscript> manganite

The thermopower, S, magnetothermopower, ΔS/S, resistivity, ρ, and magnetoresistivity, Δρ/ρ, depending on the temperature T and magnetic field H, have been studied in an Nd_0.5Sr_0.5MnO₃ single crystal consisting of three types of clusters: an antiferromagnetic CE-type with charge-orbital ordering (below the Neel temperature T_NCE ~ 145 K) and an A-type with T_NA ~ 220 K; a ferromagnetic at 234 ≤ T ≤ 252 K, and a ferromagnetic metal phase below the Curie temperature T_C = 248 K. The thermopower was found to be negative, indicating the dominance of the electronic type of conductivity. In the S(T) curves, a sharp minimum is observed in the temperature range of 100 K ≤ T ≤ 133 K, close to T_NCE, where the absolute S value attains 53 μV/K. With a further increase in temperature, the absolute S value decreases rapidly; at 200 K it is equal to 7 μV/K. It then slightly increases, reaching its maximum value of 15 μV/K at a temperature of 254 K, which is close to T_C. The absolute thermopower decreased under the influence of the magnetic field; i.e., a negative magnetothermopower occurs. In {ΔS/S}(T) curves, a sharp minimum is observed at T = 130 K close to T_NCE, where the magnetothermopower reaches a huge value of ~45% at H = 13.23 kOe. A broad minimum in the {ΔS/S}(T) curves is observed near the Curie temperature and its value is also high, viz., ~15% in the maximum measuring magnetic field of 13.23 kOe. The extremely high magnetothermopower values mean that the charge-orbital ordered nanoclusters or ferron type make the main contribution to the thermopower of the entire sample. The behavior of the ρ(T) and {Δρ/ρ}(T) curves is similar to that of the S(T) and {ΔS/S}(T) dependencies, which is in agreement with this conclusion.     

Roughness of layer interfaces and phase diagram of magnetic multilayer structures

The dependence of the type of magnetic ordering in multilayer structures on the magnitude of the exchange interaction between the magnetic layers and on the degree of roughness of the interfaces between the layers is investigated. In the case of a three-layer system the regions of existence of the domain structure, of noncollinear ordering of the homogeneous magnetic layers, and of the collinear ferromagnetic phase and collinear antiferromagnetic phase are found. Fiz. Tverd. Tela (St. Petersburg) 39, 1244–1247 (July 1997)     

Narrowing of the vibrational spectrum under compression of liquid carbon dioxide

The broadening and shift of the Q bands of the 1388/1285-cm⁻¹ Fermi doublet of carbon dioxide have been measured by means of the spectroscopy of coherent anti-Stokes Raman scattering in a wide density range realized at compression in dense gaseous and liquid states. The spectrum of the low-frequency Q band exhibits an essential narrowing upon the compression of the liquid in the density range of 320–400 amagat from a maximum width of about 2.2 cm⁻¹ to about 1.7 cm⁻¹ determined by elastic dephasing. The observed dependence is connected with the progressive narrowing of the spectral contribution attributed to the collapsed rotational structure.     

Associated φΛ0 production in the EXCHARM experiment

The features of the associated production of φ mesons with Λ⁰ hyperons in neutron-carbon interactions were investigated. The experiment was performed with the aid of the EXCHARM spectrometer at the Serpukhov accelerator in a neutron beam of energy in the interval 20–70 GeV. The differential cross section for inclusive associated φΛ⁰ production was measured.     

Effect of spontaneous frequency fluctuations on the emission line of a semiconductor laser with pseudorandom modulation of the pump current

The effect of random frequency fluctuations due to spontaneous emission and generation-recombination noise on the shape of the emission line of a semiconductor laser with pseudorandom modulation of the pump current is studied numerically. The roles of spontaneous emission and chirp modulation in forming the lasing spectrum are separated out. The dependence of the output spectral characteristics of the laser on the parameters and type of modulation is analyzed.     

Rod-climbing effect in Newtonian fluids

When a rotating rod is brought into a polymer melt or concentrated polymer solution, the meniscus climbs the rod. This spectacular rod climbing is due to the normal stresses present in the polymer fluid and is thus a purely non-Newtonian effect. A similar rod climbing of an interface between two fluids has therefore been taken as a signature that one of the fluids exhibits normal stress effects. We show here, however, that the effect can occur with simple Newtonian fluids: it occurs when a Taylor-Couette instability happens in the less viscous of the two liquids but not in the more viscous one.     

Excitation of UV radiation by a pulsed-periodic discharge in xenon

Optoelectrical characteristics of a pulsed-periodic discharge in xenon are investigated experimentally under conditions such that the product of the electrode gap length and the gas pressure is in the range of 4–20 Torr cm. High conversion efficiency of the energy deposited into vacuum UV radiation in a discharge sustained by 0.1-gms voltage pulses at a repetition rate of 1–10 kHz is demonstrated. It is shown that this effect is related to the fast expansion of the negative glow occurring after each discharge ignition. The conditions are determined under which the discharge is not accompanied by the heating and sputtering of the cathode.     

Future of low-x forward physics at RHIC

Comparisons of particle production from high-energy ion collisions with next-to-leading order perturbative QCD calculations show good agreement down to moderate transverse momentum values. Distributions of azimuthal angle differences between coincident hadrons in these collisions support a partonic origin to the particle production, again down to moderate transverse momentum values. The rapidity dependence of inclusive and coincident particle production can therefore be used to probe parton distribution functions down to small momentum fractions where theory anticipates that parton saturation could be present. This paper describes how such experiments could be completed.Arrival of the final proofs: 27 July 2005PACS: 12.38 Qk, 13.88. + e, 24.85. + p