Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Neutron diffraction study of stripe order in La(2)NiO(4+d) with d=2/15   We report a detailed neutron scattering study of the ordering of spins and
holes in oxygen-doped La(2)NiO(4.133). The single-crystal sample exhibits the
same oxygen-interstitial order but better defined charge-stripe order than that
studied previously in crystals with d = 0.125. In particular, charge order is
observed up to a temperature at least twice that of the magnetic transition,
T_m = 110.5 K. On cooling through T_m, the wave vector \epsilon, equal to half
the charge-stripe density within an NiO(2) layer, jumps discontinuously from
1/3 to 0.2944. It continues to decrease with further cooling, showing several
lock-in transitions on the way down to low temperature. To explain the observed
lock-ins, a model is proposed in which each charge stripe is centered on either
a row of Ni or a row of O ions. The model is shown to be consistent with the
l-dependence of the magnetic peak intensities and with the relative intensities
of the higher-order magnetic satellites. Analysis of the latter also provides
evidence that the magnetic domain walls (charge stripes) are relatively narrow.
In combination with a recent study of magnetic-field-induced effects, we find
that the charge stripes are all O-centered at T>T_m, with a shift towards Ni
centering at T<T_m. Inferences concerning the competing interactions
responsible for the the temperature dependence of \epsilon and the localization
of charge within the stripes are discussed.

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The categories of this paper are: patt-sol
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The categories of this paper are: acc-phys
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The categories of this paper are: hep-ph
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The categories of this paper are: q-bio
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The categories of this paper are: cs
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The categories of this paper are: gr-qc
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The categories of this paper are: solv-int
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The categories of this paper are: nlin
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The categories of this paper are: mtrl-th
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The categories of this paper are: nucl-th
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The categories of this paper are: atom-ph
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The categories of this paper are: astro-ph
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The categories of this paper are: alg-geom
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The categories of this paper are: funct-an
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The categories of this paper are: math
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The categories of this paper are: hep-lat