Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: "Wigner crystal" and "stripe" models for the magnetic and
  crystallographic superstructures of La0.333Ca0 .667MnO3   The crystallographic (charge-ordered) and magnetic superstructures of
La0.333Ca0.667MnO3 were studied by high-resolution synchrotron x-ray and
neutron powder diffraction. In the antiferromagnetic structure, which was
refined using a non-collinear model, the a lattice parameter is tripled and the
c lattice parameter is doubled with respect to the average crystallographic
unit cell (Pnma setting). The crystallographic structure below the
charge-ordering temperature (TCO ~ 260 K) is characterized by ordering of the
dz2 orbitals of the Jahn-Teller-distorted Mn3+O6 octahedra in the orthorhombic
ac plane, and the appearance of superlattice peaks in the x-ray patterns
corresponding to a tripling of the a axis lattice parameter. The intensities of
the superlattice peaks can be accounted for satisfactorily in terms of ordering
of the Mn3+ cations in sites as far apart as possible in the ac plane ("Wigner
crystal" model) and transverse displacements of the Mn4+O6 octahedra in the c
direction. These results are not consistent with a recently proposed model
based on transmission electron microscopy (TEM) data in which the Mn3+O6
octahedra are arranged in a stripe pattern ("stripe" model). In particular, the
large longitudinal stripe modulation revealed by TEM is not observed,
suggesting that the TEM data may not be representative of the bulk sample.
Within the framework of the "Wigner crystal" model, the magnetic structure at
1.5 K and the charge-ordered superstructure at 160 K and 1.5 K were refined
from the neutron data.

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The categories of this paper are: hep-lat
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The categories of this paper are: cs
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The categories of this paper are: solv-int
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The categories of this paper are: nucl-th
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The categories of this paper are: ao-sci
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The categories of this paper are: math-ph
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The categories of this paper are: q-alg
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The categories of this paper are: hep-ph
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The categories of this paper are: eess
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The categories of this paper are: funct-an
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The categories of this paper are: econ
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The categories of this paper are: adap-org
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The categories of this paper are: stat
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The categories of this paper are: mtrl-th
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The categories of this paper are: supr-con
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The categories of this paper are: acc-phys