60 research outputs found
The charge ordered state in half-doped Bi-based manganites studied by O and Bi NMR
We present a Bi and O NMR study of the Mn electron spin
correlations developed in the charge ordered state of
BiSrMnO and BiCaMnO. The unusually
large local magnetic field indicates the dominant
character of the lone electron pair of Bi-ions in both compounds. The
mechanism connecting the character of the lone pairs to the high
temperature of charge ordering is still not clarified. The observed
difference in for BiSrMnO to
BiCaMnO is probably due to a decrease in the canting of
the staggered magnetic moments of Mn-ions from. The modification of the
O spectra below demonstrates that the line due to the apical
oxygens is a unique local tool to study the development of the Mn spin
correlations. In the AF state the analysis of the O spectrum of
PrCaMnO and BiSrMnO prompts us to
try two different theoretical descriptions of the charge-ordered state, a
site-centered model for the first manganite and a bond-centered model for the
second one.Comment: 10 pages, 7 figure
Representations for Three-Body T-Matrix on Unphysical Sheets: Proofs
A proof is given for the explicit representations which have been formulated
in the author's previous work (nucl-th/9505028) for the Faddeev components of
three-body T-matrix continued analytically on unphysical sheets of the energy
Riemann surface. Also, the analogous representations for analytical
continuation of the three-body scattering matrices and resolvent are proved. An
algorithm to search for the three-body resonances on the base of the Faddeev
differential equations is discussed.Comment: 98 Kb; LaTeX; Journal-ref was added (the title changed in the
journal
Representations for Three-Body T-Matrix on Unphysical Sheets
Explicit representations are formulated for the Faddeev components of
three-body T-matrix continued analytically on unphysical sheets of the energy
Riemann surface. According to the representations, the T-matrix on unphysical
sheets is obviously expressed in terms of its components taken on the physical
sheet only. The representations for T-matrix are used then to construct similar
representations for analytical continuation of three-body scattering matrices
and resolvent. Domains on unphysical sheets are described where the
representations obtained can be applied.Comment: 123 Kb; LaTeX; Journal-ref was added (the title changed in the
journal
Structure of boson systems beyond the mean-field
We investigate systems of identical bosons with the focus on two-body
correlations. We use the hyperspherical adiabatic method and a decomposition of
the wave function in two-body amplitudes. An analytic parametrization is used
for the adiabatic effective radial potential. We discuss the structure of a
condensate for arbitrary scattering length. Stability and time scales for
various decay processes are estimated. The previously predicted Efimov-like
states are found to be very narrow. We discuss the validity conditions and
formal connections between the zero- and finite-range mean-field
approximations, Faddeev-Yakubovskii formulation, Jastrow ansatz, and the
present method. We compare numerical results from present work with mean-field
calculations and discuss qualitatively the connection with measurements.Comment: 26 pages, 6 figures, submitted to J. Phys. B. Ver. 2 is 28 pages with
modified figures and discussion
73Ge NMR spectra in germanium single crystals with different isotopic composition
We have studied the influence of isotopic disorder on the local deformations in Ge single crystals from both experimental and calculation points of view. The nuclear magnetic resonance (NMR) spectra of 73Ge nuclei (the nuclear spin equals 9/2) in perfect single crystals of germanium with different isotopic content were measured at temperatures 80, 300 and 450 K. Abnormal broadening of the spectrum was found to occur when the magnetic field was aligned along the [111] axis of a crystal. The observed specific angular dependence of the quadrupole broadening was attributed to isotopic disorder among atoms of germanium sited around the 73Ge NMR probe. Local lattice deformations in germanium crystal lattice due to isotopic impurity atoms were calculated in the framework of the adiabatic bond charge model. The results obtained were applied to study random noncubic crystal field interactions with the nuclear quadrupole moments and corresponding effects in NMR spectra. Simulated second and fourth moments of resonance frequency distributions caused by the magnetic dipole-dipole and electric quadrupole interactions are used to analyze the lineshapes, theoretical predictions agree qualitatively with the experimental data. © Springer-Verlag 1999
Magnetic relaxation in La0.250Pr0.375Ca0.375MnO3 with varying phase separation
We have studied the magnetic relaxation properties of the phase-separated
manganite compound La0.250Pr0.375Ca0.375MnO3 . A series of polycrystalline
samples was prepared with different sintering temperatures, resulting in a
continuous variation of phase fraction between metallic (ferromagnetic) and
charge-ordered phases at low temperatures. Measurements of the magnetic
viscosity show a temperature and field dependence which can be correlated to
the static properties. Common to all the samples, there appears to be two types
of relaxation processes - at low fields associated with the reorientation of
ferromagnetic domains and at higher fields associated with the transformation
between ferromagnetic and non-ferromagnetic phases.Comment: 30 pages with figures, PDF, accepted to be published in Physical
Review
Heat transfer and vaporization in the boiling of a surfactant solution in steam generators
Examination of the efficiency of welded joints in 10G2BT pipes steel produced by two-pass laser welding
Translated from Ukrainian? (Avtom. Svarka 1995 (7) p. 12-17)Available from British Library Document Supply Centre-DSC:9023.190((VR-Trans--8989)T / BLDSC - British Library Document Supply CentreSIGLEGBUnited Kingdo
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