Existence Of Short-range Correlations Research Articles

Synthesis and Characterization of Sodium-Iron Antimonate Na2FeSbO5: One-Dimensional Antiferromagnetic Chain Compound with a Spin-Glass Ground State.

A new oxide, sodium-iron antimonate, Na2FeSbO5, was synthesized and structurally characterized, and its static and dynamic magnetic properties were comprehensively studied both experimentally by dc and ac magnetic susceptibility, magnetization, specific heat, electron spin resonance (ESR) and Mössbauer measurements, and theoretically by density functional calculations. The resulting single-crystal structure (a = 15.6991(9) Å; b = 5.3323 (4) Å; c = 10.8875(6) Å; S.G. Pbna) consists of edge-shared SbO6 octahedral chains, which alternate with vertex-linked, magnetically active FeO4 tetrahedral chains. The 57Fe Mössbauer spectra confirmed the presence of high-spin Fe3+ (3d5) ions in a distorted tetrahedral oxygen coordination. The magnetic susceptibility and specific heat data show the absence of a long-range magnetic ordering in Na2FeSbO5 down to 2 K, but ac magnetic susceptibility unambigously demonstrates spin-glass-type behavior with a unique two-step freezing at Tf1 ≈ 80 K and Tf2 ≈ 35 K. Magnetic hyperfine splitting of 57Fe Mössbauer spectra was observed below T* ≈ 104 K (Tf1 < T*). The spectra just below T* (Tf1 < T < T*) exhibit a relaxation behavior caused by critical spin fluctuations, indicating the existence of short-range correlations. The stochastic model of ionic spin relaxation was used to account for the shape of the Mössbauer spectra below the freezing temperature. A complex slow dynamics is further supported by ESR data revealing two different absorption modes presumably related to ordered and disordered segments of spin chains. The data imply a spin-cluster ground state for Na2FeSbO5.

Role of short-range correlation in facilitation of wave propagation in a long-range ladder chain

We extend a new method for generating a random chain, which has a kind of short-range correlation induced by a repeated sequence while retaining long-range correlation. Three distinct methods are considered to study the localization–delocalization transition of mechanical waves in one-dimensional disordered media with simultaneous existence of short and long-range correlation. First, a transfer-matrix method was used to calculate numerically the localization length of a wave in a binary chain. We found that the existence of short-range correlation in a long-range correlated chain can increase the localization length at the resonance frequency Ωc. Then, we carried out an analytical study of the delocalization properties of the waves in correlated disordered media around Ωc. Finally, we apply a dynamical method based on the direct numerical simulation of the wave equation to study the propagation of waves in the correlated chain. Imposing short-range correlation on the long-range background will lead the propagation to super-diffusive transport. The results obtained with all three methods are in agreement with each other.

The Recurrence Interval Difference of Power Load in Heavy/Light Industries of China

The significant fluctuation of industrial electricity consumption has a high impact on power load, which makes the research on recurrence intervals between extreme events of theoretical and practical significance. The study uses a high-frequency data of heavy and light industries and employs recurrence interval analysis in different thresholds. We find that the reoccurrence interval of volatility can fit with the stretched exponential function and the probability density functions of recurrence intervals in various thresholds shows a scaling behavior. Then, the conditional probability density function and the multifractal detrended fluctuation analysis demonstrate the existence of short-range correlation, long-range correlation, and multifractal properties, respectively. We further construct a hazard function, introduce recurrence intervals into VaR calculation and establish a functional relationship between average recurrence interval and threshold. Following this result, we also shed light on policy discussion for multi-industrial electricity supply management.

Palmer-Chalker correlations in theXYpyrochlore antiferromagnet Er2Sn2O7

\ersn\, is considered, together with \erti, as a realization of the XY antiferromagnet on the pyrochlore lattice. We present magnetization measurements confirming that \ersn\, does not order down to 100 mK but exhibits a freezing below 200 mK. Our neutron scattering experiments evidence the strong XY character of the \er moment and point out the existence of short range correlations in which the magnetic moments are in peculiar configurations, the Palmer-Chalker states, predicted theoretically for an XY pyrochlore antiferromagnet with dipolar interactions. Our estimation of the \ersn\, parameters confirm the role of the latter interactions on top of relatively weak and isotropic exchange couplings.

Magnetic Glassiness below Curie Temperature in La0.8Ca0.2MnO3

The magnetic and structural behaviors of a single crystal of La 0.8 Ca 0.2 MnO 3 were investigated in terms of magnetic and neutron diffraction measurements. The frequency-dependent ac magnetic susceptibility reveals that cluster-glassy phase evolves below the Curie temperature ( T C ) in this system, suggesting the existence of short-range correlation below T C embedded in the ferromagnetic (FM) background. A correlation of the magnetic properties in La 0.8 Ca 0.2 MnO 3 with the buckling of MnO 6 octahedra is discussed based on its temperature-dependent neutron and magnetization data.

Two- and three-particle correlations in gold-emulsion interactions at 10.6A GeV

We present an analysis on two- and three-particle correlations among shower particles, produced in semi-central collisions of197Au at 10.6A GeV with nuclear emulsion. Results are compared with the existing data of28Si ion at 14.5A GeV from BNL, and32S,16O nuclei at 200A GeV and16O beam at 60A GeV from CERN. Existence of short-range correlations is observed to be a general feature of all the heavy-ion reactions in pseudorapidity and azimuthal angle phase-spaces.

Axial polarizability and weak currents in nuclei

The effect of the isobaric excitations on the weak axial coupling constants in nuclei is studied through P.C.A.C. We first establish the Klein-Gordon equation for the virtual pion field in the nucleus; it takes into account pion rescattering. The influence of isobar excitation is contained in the axial polarizability coefficient which is linked to the p-wave π- N scattering volume. The derivation of this equation stresses its analogies with electromagnetism. We give then a basic relation between the axial current and the pionic field. It incorporates the effects of the isobars in the axial polarizability, which leads naturally to an electromagnetic analog. We show that this relation leads in heavy nuclei to a quenching of the axial coupling constant by the Lorentz-Lorenz factor, which may originate from the short range or the Pauli correlations, depending on the range of the π- N forces. Hence this quenching may have a different origin than the existence of short-range correlations and may arise from a Pauli blocking effect. On the other hand, the pseudoscalar coupling constant is found to be strongly suppressed. In finite nuclei, these basic quenchings can be masked by surface effects, the general features of which are studied with the help of a solvable model. This model is further used to obtain the asymptotic pion field which is linked to the effective pion-nucleus coupling constant and can be determined experimentally through π-nucleus dispersion relations. We find that this quantity is quenched, in agreement with recent experimental data.