Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Systematic ^{75}As NMR study of the dependence of low-lying excitations
  on F doping in the iron oxypnictide LaFeAs(O_{1-x}F_{x})   We report systematic $^{75}$As NMR studies on LaFeAs(O$_{1-x}$F$_{x}$) ($0\le
x\le0.14$). At $x=0.04$ near the phase boundary, from resistivity, spin-lattice
relaxation rate $1/T_1$, and NMR spectrum measurements, we found weak magnetic
order at $T_N\simeq 30$ K. Antiferromagnetic (AFM) fluctuations proved through
$1/T_1$ are suppressed significantly with F-doping, and pseudogap behavior
without pronounced AFM fluctuations is observed at $x=0.11$ where $T_c$ is
maximum. This significant suppression of $1/T_1T$ upon F-doping while $T_c$
remains nearly unchanged suggests that low-energy AFM fluctuations probed with
$^{75}$As NMR do not play a crucial role in the superconductivity.

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The categories of this paper are: adap-org
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The categories of this paper are: math-ph
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The categories of this paper are: eess
34
The categories of this paper are: chem-ph
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The categories of this paper are: nucl-th
10
The categories of this paper are: q-bio
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The categories of this paper are: cs
3
The categories of this paper are: physics
33
The categories of this paper are: plasm-ph
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The categories of this paper are: nucl-ex
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The categories of this paper are: hep-lat
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The categories of this paper are: comp-gas
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The categories of this paper are: hep-th
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The categories of this paper are: nlin
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The categories of this paper are: bayes-an
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The categories of this paper are: patt-sol