1,719 research outputs found
13C NMR study of the magnetic properties of the quasi-one-dimensional conductor, (TMTTF)2SbF6
Magnetic properties in the quasi-one-dimensional organic salt (TMTTF)2SbF6
are investigated by 13C NMR under pressures. Antiferromagnetic phase transition
at ambient pressure (AFI) is confirmed. Charge-ordering is suppressed by
pressure and is not observed under 8 kbar. For 5 < P < 20 kbar, a sharp
spectrum and the rapid decrease of the spin-lattice relaxation rate 1/T1 were
observed below about 4 K, attributed to a spin-gap transition. Above 20 kbar,
extremely broadened spectrum and critical increase of 1/T1 were observed. This
indicates that the system enters into another antiferromagnetic phase (AFII)
under pressure. The slope of the antiferromagnetic phase transition temperature
T_AFII, dT_AFII/dP, is positive, while T_AFI decreases with pressure. The
magnetic moment is weakly incommensurate with the lattice at 30 kbar.Comment: 8 pages, 9 figures, to appear in Phys. Rev.
Topology of multiple log transforms of 4-manifolds
Given a 4-manifold X and an imbedding of T^{2} x B^2 into X, we describe an
algorithm X --> X_{p,q} for drawing the handlebody of the 4-manifold obtained
from X by (p,q)-logarithmic transforms along the parallel tori. By using this
algorithm, we obtain a simple handle picture of the Dolgachev surface
E(1)_{p,q}, from that we deduce that the exotic copy E(1)_{p,q} # 5(-CP^2) of
E(1) # 5(-CP^2) differs from the original one by a codimension zero simply
connected Stein submanifold M_{p,q}, which are therefore examples of infinitely
many Stein manifolds that are exotic copies of each other (rel boundaries).
Furthermore, by a similar method we produce infinitely many simply connected
Stein submanifolds Z_{p} of E(1)_{p,2} # 2(-CP^2)$ with the same boundary and
the second Betti number 2, which are (absolutely) exotic copies of each other;
this provides an alternative proof of a recent theorem of the author and Yasui
[AY4]. Also, by using the description of S^2 x S^2 as a union of two cusps
glued along their boundaries, and by using this algorithm, we show that
multiple log transforms along the tori in these cusps do not change smooth
structure of S^2 x S^2.Comment: Updated, with 17 pages 21 figure
Sulphur potential measurements with a two-phase sulphideoxide electrolyte
The open circuit potentials of the galvanic cell,Pt
(or Au)|(Ar + H2S + H2)'||CaS +
ZrO2(CaO)|| (Ar + H2S+
H2)"|Pt (or Au) has been measured in the
temperature range 1000 to 1660 K and
PH2S:PH 2 ratios
from 1.73×10-5 to 2.65×10-1.
The solid electrolyte consists of a dispersion of calcium
sulphide in a matrix of calcia-stabilized zirconia. The
surface of the electrolyte is coated with a thin layer of
calcium sulphide to prevent the formation of water vapour by
reaction of hydrogen sulphide with calcium oxide or zirconia
present in the electrolyte. The use of a point electrode with
a catalytically active tip was necessary to obtain steady
emfs. At low temperatures and high sulphur potentials the
emfs agreed with the Nernst equation. Deviations were
observed at high temperatures and low sulphur potentials,
probably due to the onset of significant electronic
conduction in the oxide matrix of the electrolyte. The values
of oxygen and sulphur potentials at which the electronic
conductivity is equal to ionic conductivity in the two-phase
electrolyte have been evaluated from the emf response of the
cell. The sulphide-oxide electrolyte is unsuitable for
sulphur potential measurements in atmospheres with high
oxygen potentials, where oxidation of calcium sulphide may be
expected
Orbital Order Effect of Two-Dimensional Spin Gap System for CaV4O9
Effects of possible orbital order in magnetic properties of two-dimensional
spin gap system for CaVO are investigated theoretically. After
analyzing experimental data, we show that single orbital models assumed in the
literature are insufficient to reproduce the data. To understand the origin of
the discrepancy, we assume that in state of V, and
orbitals have substantial contributions in the lowest-energy atomic level which
leads to a double-degeneracy. We study possible configurations of the orbital
order. By exact diagonalization and perturbation expansion, we calculate the
susceptibility, wavenumber dependence of low-lying excitations and equal-time
spin-spin correlations which is related to integrated intensity of the neutron
inelastic scattering. These quantities sensitively depend on the configuration
of the orbital order. The calculated results for some configurations of the
orbital order reproduce many experimental results much better than the previous
single-orbital models. However some discrepancy still remains to completely
reproduce all of the reported experimental results. To understand the origin of
these discrepancies, we point out the possible importance of the partially
occupied orbital in addition to orbital order of partially filled
and orbitals.Comment: 19 pages LATEX, 15 postscript figures, using jpsj.sty,to be published
in J.Phys.Soc.Jpn. Vol.67 No.2 (1998
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