Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Intraplanar Magnetic Excitations in Na0.5CoO2: An Inelastic Neutron
  Study   Inelastic neutron scattering measurements mapping the in-plane magnetic
interactions of Na0.5CoO2 reveal dispersive excitations at points above an
energy gap Eg = 11.5(5) meV at the superstructural Bragg reflections. The
excitations are highly damped, broadening with increasing energy, and disappear
at hw ~ 35 meV, a strong indication that the magnetism is itinerant. Tilting
into the ac plane reduces the value of Eg by 25%, suggesting that the
dispersion along c is significant and the magnetic correlations are
three-dimensional, as seen at the higher doping levels.

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The categories of this paper are: acc-phys
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The categories of this paper are: supr-con
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The categories of this paper are: patt-sol
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The categories of this paper are: solv-int
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The categories of this paper are: eess
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The categories of this paper are: hep-ex
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The categories of this paper are: q-fin
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The categories of this paper are: nucl-ex
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The categories of this paper are: dg-ga
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The categories of this paper are: q-bio
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The categories of this paper are: math
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The categories of this paper are: q-alg
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The categories of this paper are: bayes-an
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The categories of this paper are: funct-an
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The categories of this paper are: cmp-lg
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The categories of this paper are: plasm-ph