45,749 research outputs found
The suppression of superconductivity in Mn substituted MgCNi
We report the effect of doping Mn in the isostructural MgCNiMn
(x = 0-0.05) compounds. Magnetic susceptibility, resistivity,
magneto-resistance, and specific heat studies show evidence of localized
moments and Kondo effect in samples with x0. The rapid suppression of
superconductivity ( -21K/at.% Mn) in these compounds is a consequence of
pair breaking effects due to moment formation on Mn.Comment: 9 figures, Accepted for publication in Physical Review B, Added
reference
Voltage bias induced modification of all oxide Pr0.5Ca0.5MnO3/SrTi0.95Nb.05O3 junctions
In this paper we report what happens to a pristine oxide junction
Pr0.5Ca0.5MnO3/SrTi0.95Nb.05O3 (PCMO/Nb:STO), when it is subjected to cycling
of voltage bias of moderate value ({\pm}4V). It is found that the initial
cycling leads to formation of a permanent state of lower resistance where the
lower resistance arises predominantly due to development of a shunt across the
device film (PCMO). On successive voltage cycling with increasing magnitude,
this state transforms into states of successive lower resistance that can be
transformed back to the initial stable state on cycling to below a certain
bias. A simple model based on p-n junction with shunt has been used to obtain
information on the change of the junction on voltage cycling. It has been shown
that the observation can be explained if the voltage cycling leads to lowering
of barrier at the interface and also reduction in series resistance. It is
suggested that this lowering can be related to the migration of oxygen ions and
vacancies at the junction region. Cross-sectional imaging of the junction shows
formation of permanent filamentary bridges across the thickness of the PCMO
after the pristine p-n junction is first taken through a voltage cycle, which
would explain appearance of a finite shunt across the p-n junction.Comment: 12 pages,7figure
Competition of L21 and XA Ordering in Fe2CoAl Heusler Alloy: A First-Principles Study
The physical properties of Fe2CoAl (FCA) Heusler alloy are systematically
investigated using the first-principles calculations within generalized
gradient approximation (GGA) and GGA+U. The influence of atomic ordering with
respect to the Wyckoff sites on the phase stability, magnetism and half
metallicity in both the conventional L21 and XA phases of FCA is focused in
this study. Various possible hypothetical structures viz., L21, XA-I, and XA-II
are prepared by altering atomic occupancies at their Wyckoff sites. At first,
we have determined the stable phase of FCA considering various non-magnetic (or
paramagnetic), ferromagnetic (FM) and antiferromagnetic (AFM) configurations.
Out of these, the ferromagnetic (FM) XA-I structure is found to be
energetically most stable. The total magnetic moments per cell are not in
agreement with the Slater-Pauling (SP) rule in any phases; therefore, the
half-metallicity is not observed in any configurations. However, FM ordered
XA-I type FCA shows 78% spin polarization at EF. Interestingly, the results of
XA-I type FCA are closely matched with the experimental results.Comment: 15 pages, 6 figure
Thermal field theory derivation of the source term induced by a fast parton from the quark energy-momentum tensor
I derive the distribution of energy and momentum transmitted from a fast
parton to a medium of thermalized quarks, or the source term, in perturbative
thermal field theory directly from the quark energy-momentum tensor. The fast
parton is coupled to the medium by adding an interaction term to the
Lagrangian. The thermal expectation value of the energy-momentum tensor source
term is then evaluated using standard Feynman rules at finite temperature. It
is found that local excitations, which are important for exciting an observable
Mach cone structure, fall sharply as a function of the energy of the fast
parton. This may have implications for the trigger dependence of
measurements of azimuthal dihadron particle correlations in heavy-ion
collisions. In particular, a conical emission pattern would be less likely to
be observed for increasing trigger . I show that the results presented in
this paper can be generalized to more realistic modeling of fast parton
propagation, such as through a time dependent interaction term, in future
studies.Comment: Version as accepted by Physical Review D. New version has several
clarifications and added references. 5 pages, 3 figure
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