Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Competing effects of Mn and Y doping on the low-energy excitations and
  phase diagram of La$_{1-y}$Y$_{y}$Fe$_{1-x}$Mn$_x$AsO$_{0.89}$F$_{0.11}$
  iron-based superconductors   Muon Spin Rotation ($\mu$SR) and $^{19}$F Nuclear Magnetic Resonance (NMR)
measurements were performed to investigate the effect of Mn for Fe
substitutions in La$_{1-y}$Y$_{y}$Fe$_{1-x}$Mn$_x$AsO$_{0.89}$F$_{0.11}$
superconductors. While for $y = 0$ a very low critical concentration of Mn ($x
= 0.2$%) is needed to quench superconductivity, as $y$ increases the negative
chemical pressure introduced by Y for La substitution stabilizes
superconductivity and for $y= 20$% it is suppressed at Mn contents an order of
magnitude larger. A magnetic phase arises once superconductivity is suppressed
both for $y$=0 and for $y= 20$%. Low-energy spin fluctuations give rise to a
peak in $^{19}$F NMR $1/T_1$ with an onset well above the superconducting
transition temperature and whose magnitude increases with $x$. Also the static
magnetic correlations probed by $^{19}$F NMR linewidth measurements show a
marked increase with Mn content. The disruption of superconductivity and the
onset of the magnetic ground-state are discussed in the light of the proximity
of LaFeAsO$_{0.89}$F$_{0.11}$ to a quantum critical point.

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The categories of this paper are: chem-ph
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The categories of this paper are: solv-int
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The categories of this paper are: adap-org
13
The categories of this paper are: quant-ph
2
The categories of this paper are: math
24
The categories of this paper are: dg-ga
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The categories of this paper are: comp-gas
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The categories of this paper are: cmp-lg
3
The categories of this paper are: physics
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The categories of this paper are: nucl-ex
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The categories of this paper are: stat
0
The categories of this paper are: hep-ph
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The categories of this paper are: hep-ex
5
The categories of this paper are: gr-qc
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The categories of this paper are: econ
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The categories of this paper are: mtrl-th