4,124 research outputs found
Intrinsic interface exchange coupling of ferromagnetic nanodomains in a charge ordered manganite
We present a detailed magnetic study of the Pr1/3Ca2/3MnO3 manganite, where
we observe the presence of small ferromagnetic (FM) domains (diameter ~ 10A)
immersed within the charge-ordered antiferromagnetic (AFM) host. Due to the
interaction of the FM nanodroplets with a disordered AFM shell, the
low-temperature magnetization loops present exchange bias (EB) under cooling in
an applied magnetic field. Our analysis of the cooling field dependence of the
EB yields an antiferromagnetic interface exchange coupling comparable to the
bulk exchange constant of the AFM phase. We also observe training effect of the
EB, which is successfully described in terms of a preexisting relaxation model
developed for other classical EB systems. This work provides the first evidence
of intrinsic interface exchange coupling in phase separated manganites.Comment: 7 pages, 6 figure
Critical behavior of Griffiths ferromagnets
From a heuristic calculation of the leading order essential singularity in
the distribution of Yang-Lee zeroes, we obtain new scaling relations near the
ferromagnetic-Griffiths transition, including the prediction of a discontinuity
on the analogue of the critical isotherm. We show that experimental data for
the magnetization and heat capacity of are
consistent with these predictions, thus supporting its identification as a
Griffiths ferromagnet.Comment: 4 pages, 3 figures, Changed conten
Nanoscale magnetic structure of ferromagnet/antiferromagnet manganite multilayers
Polarized Neutron Reflectometry and magnetometry measurements have been used
to obtain a comprehensive picture of the magnetic structure of a series of
La{2/3}Sr{1/3}MnO{3}/Pr{2/3}Ca{1/3}MnO{3} (LSMO/PCMO) superlattices, with
varying thickness of the antiferromagnetic (AFM) PCMO layers (0<=t_A<=7.6 nm).
While LSMO presents a few magnetically frustrated monolayers at the interfaces
with PCMO, in the latter a magnetic contribution due to FM inclusions within
the AFM matrix was found to be maximized at t_A~3 nm. This enhancement of the
FM moment occurs at the matching between layer thickness and cluster size,
where the FM clusters would find the optimal strain conditions to be
accommodated within the "non-FM" material. These results have important
implications for tuning phase separation via the explicit control of strain.Comment: 4 pages, submitted to PR
A Penetration Depth Study on Li2Pd3B and Li2Pt3B
In this paper we present a penetration depth study on the newly discovered
superconductors LiPdB and LiPtB. Surprisingly, the
low-temperature penetration depth demonstrates distinct behavior in
these two isostructural compounds. In LiPdB, follows an
exponential decay and can be nicely fitted by a two-gap BCS superconducting
model with a small gap K and a large gap K.
However, linear temperature dependence of is observed in LiPtB
below 0.3, giving evidence of line nodes in the energy gap.Comment: 2 pages, submitted to LT2
On the Moyal deformation of Nahm Equations in seven dimensions
We show how the reduced (anti-)self-dual Yang-Mills equations in seven
dimensions described by the Nahm equations can be carried over to the
Weyl-Wigner-Moyal formalism. In the process some new solutions for the cases of
gauge groups SU(2) and SL(2,R) are explicitly obtained.Comment: 16+1 pages, LaTeX, no figure
Floer Homology and the Heat Flow
Abstract.: We study the heat flow in the loop space of a closed Riemannian manifold M as an adiabatic limit of the Floer equations in the cotangent bundle. Our main application is a proof that the Floer homology of the cotangent bundle, for the Hamiltonian function kinetic plus potential energy, is naturally isomorphic to the homology of the loop spac
Reversible Superconductivity in Electrochromic Indium-Tin Oxide Films
Transparent conductive indium tin oxide (ITO) thin films, electrochemically
intercalated with sodium or other cations, show tunable superconducting
transitions with a maximum at 5 K. The transition temperature and the
density of states, (extracted from the measured Pauli susceptibility
exhibit the same dome shaped behavior as a function of electron
density. Optimally intercalated samples have an upper critical field T and . Accompanying the development of
superconductivity, the films show a reversible electrochromic change from
transparent to colored and are partially transparent (orange) at the peak of
the superconducting dome. This reversible intercalation of alkali and alkali
earth ions into thin ITO films opens diverse opportunities for tunable,
optically transparent superconductors
Lamellar phase separation and dynamic competition in La0.23Ca0.77MnO3
We report the coexistence of lamellar charge-ordered (CO) and
charge-disordered (CD) domains, and their dynamical behavior, in
La0.23Ca0.77MnO3. Using high resolution transmission electron microscopy (TEM),
we show that below Tcd~170K a CD-monoclinic phase forms within the established
CO-orthorhombic matrix. The CD phase has a sheet-like morphology, perpendicular
to the q vector of the CO superlattice (a axis of the Pnma structure). For
temperatures between 64K and 130K, both the TEM and resistivity experiments
show a dynamic competition between the two phases: at constant T, the CD phase
slowly advances over the CO one. This slow dynamics appears to be linked to the
magnetic transitions occurring in this compound, suggesting important
magnetoelastic effects.Comment: 4 pages, 4 figure
Subspaces of a para-quaternionic Hermitian vector space
Let be a para-quaternionic Hermitian structure on the real
vector space . By referring to the tensorial presentation , we
give an explicit description, from an affine and metric point of view, of main
classes of subspaces of which are invariantly defined with respect to the
structure group of and respectively
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