An adaptive algorithm for n-body field expansions
Weinberg, Martin D.
1998-05-28
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12 records were found.
Comment: 4 pages, 5 figures
Comment: 4 pages, 5 figures
Comment: 4 pages, 4 eps figures, to be published in Phys. Rev. Lett
We describe the evolution of the static and dynamic spin correlations of
La$_{1-x}$Ca$_x$MnO$_3$, for x=0.1, 0.125 and 0.2, where the system evolves
from the canted magnetic state towards the insulating ferromagnetic state,
approaching the metallic transition (x=0.22).
In the x=0.1 sample, the observation of two spin wave branches typical of two
distinct types of magnetic coupling, and of a modulation in the elastic diffuse
scattering characteristic of ferromagnetic inhomogeneities, confirms the static
and dynamic inhomogeneous features previously observed at x$<$0.1. The
anisotropic q-dependence of the intensity of the low-energy spin wave suggests
a bidimensionnal character for the static inhomogeneities. At x=0.125, which
corresponds to the occurence of a ferromagnetic and insulating state, the two
spin wave branches reduce to a ...
The ferromagnetic and insulating state observed in La$_{1-x}$Ca$_{x}$MnO$_3$,
0.125$<$x$<$0.2, is characterized by structural and magnetic anomalies below
T$_C$, similar to those observed in the x$_{Sr}$$\approx$1/8. A neutron
scattering study of the superlattice {\bf Q$_0$}= (0,0,1+/4)$_{cub}$ peak, and
of the magnetic excitations are reported in the x$_{Ca}$=0.2 sample. The
occurrence of this superstructure is associated with the observation of a gap
in the spin dynamics, at a {\bf q$_0$} wave-vector ({\bf q$_0$}={\bf
Q$_0$}-$\tau$) with the same modulus $|${\bf q$_0$}$|$ in all directions, which
divides the dispersion into two regimes. For $|${\bf q}$|$$<$$|${\bf q$_0$}$|$
the dispersion is splitted into two or three curves. For $|${\bf
q}$|$$>$$|${\bf q$_0$}$|$, magnetic excitations lock on acoustic and optic
phonon energies, rev...
The effect of resistive switching in doped manganites being in the
ferromagnetic state has been studied using resistive and magneto-optic methods.
The visualization of magnetic structure of La0.75Sr0.25MnO3-x single crystals,
and its transformation under electric current proposed local superheating of
the material above the Curie temperature, which was supported by numerical
calculation. The obtained results suggest a significant role of
micrometer-scale inhomogeneity of manganites in phase separation, magnetic and
transport properties of the material.
Comment: 11 pages, 7 figures, submitted to Phys. Rev. B
Comment: 4 pages (RevTex), 3 figures (encapsulated postscript)
Comment: 6 pages, including 3 figures; revised version; Europhys. Lett.
(http://epljournal.edpsciences.org/), in press
Comment: published in Physical Rev. B 78, 212301 (2008)
