388 research outputs found
Huge Seebeck coefficients in non-aqueous electrolytes
The Seeebeck coefficients of the non-aqueous electrolytes tetrabutylammonium
nitrate, tetraoctylphosphonium bromide and tetradodecylammonium nitrate in
1-octanol, 1-dodecanol and ethylene-glycol are measured in a temperature range
from T=30 to T=45 C. The Seebeck coefficient is generally of the order of a few
hundreds of microvolts per Kelvin for aqueous solution of inorganic ions. Here
we report huge values of 7 mV/K at 0.1M concentration for tetrabutylammonium
nitrate in 1-dodecanol. These striking results open the question of
unexpectedly large kosmotrope or "structure making" effects of
tetraalkylammonium ions on the structure of alcohols.Comment: Submitted to J. Chem. Phy
Intrinsic Low Temperature Paramagnetism in B-DNA
We present experimental study of magnetization in -DNA in
conjunction with structural measurements. The results show the surprising
interplay between the molecular structures and their magnetic property. In the
B-DNA state, -DNA exhibits paramagnetic behaviour below 20 K that is
non-linear in applied magnetic field whereas in the A-DNA state, remains
diamagnetic down to 2 K. We propose orbital paramagnetism as the origin of the
observed phenomena and discuss its relation to the existence of long range
coherent transport in B-DNA at low temperature.Comment: 5 pages, 4 figures, submitted to Physical Review Letters October 200
Thermopower peak in phase transition region of (1-x)LaCaMnO/xYSZ
The thermoelectric power (TEP) and the electrical resistivity of the
intergranular magnetoresistance (IGMR) composite,
(1-x)LaCaMnO/xYSZ (LCMO/YSZ) with x = 0, 0.75%, 1.25%,
4.5%, 13% 15% and 80% of the yttria-stabalized zirconia (YSZ), have been
measured from 300 K down to 77 K. Pronounced TEP peak appears during the phase
transition for the samples of x 0, while not observed for x = 0. We suggest
that this is due to the magnetic structure variation induced by the lattice
strain which is resulting from the LCMO/YSZ boundary layers. The transition
width in temperature derived from , with being the AC magnetic
susceptibility, supports this interpretation.Comment: 4 pages, 4 eps figures, Latex, J. Appl. Phys 94, 7206 (2003
Noise Measurement of Interacting Ferromagnetic Particles with High Resolution Hall Microprobes
We present our first experimental determination of the magnetic noise of a
superspinglass made of < 1 pico-liter frozen ferrofluid. The measurements were
performed with a local magnetic field sensor based on Hall microprobes operated
with the spinning current technique. The results obtained, though preliminary,
qualitatively agree with the theoretical predictions of Fluctuation-Dissipation
theorem (FDT) violation [1].Comment: 4pages, 2 figure
Doping-dependent evolution of low-energy excitations and quantum phase transitions within effective model for High-Tc copper oxides
In this paper a mean-field theory for the spin-liquid paramagnetic
non-superconducting phase of the p- and n-type High- cuprates is
developed. This theory applied to the effective model with the
{\it ab initio} calculated parameters and with the three-site correlated
hoppings. The static spin-spin and kinematic correlation functions beyond
Hubbard-I approximation are calculated self-consistently. The evolution of the
Fermi surface and band dispersion is obtained for the wide range of doping
concentrations . For p-type systems the three different types of behavior
are found and the transitions between these types are accompanied by the
changes in the Fermi surface topology. Thus a quantum phase transitions take
place at and at . Due to the different Fermi surface topology
we found for n-type cuprates only one quantum critical concentration, .
The calculated doping dependence of the nodal Fermi velocity and the effective
mass are in good agreement with the experimental data.Comment: 8 page
Growth of a dynamical correlation length in an aging superspin glass
We report on zero field cooled magnetization relaxation experiments on a
concen- trated frozen ferrofluid exhibiting a low temperature superspin glass
transition. With a method initially developed for spin glasses, we investigate
the field dependence of the relaxations that take place after different aging
times. We extract the typical number of correlated spins involved in the aging
dynamics. This brings important insights into the dynamical correlation length
and its time growth. Our results, consistent with expressions obtained for spin
glasses, extend the generality of these behaviours to the class of superspin
glasses. Since the typical flipping time is much larger for superspins than for
atomic spins, our experiments probe a time regime much closer to that of
numerical simulations
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