Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: NMR Study of the New Magnetic Superconductor CaK(Fe$0.951Ni0.049)4As4:
  Microscopic Coexistence of Hedgehog Spin-vortex Crystal and Superconductivity   Coexistence of a new-type antiferromagnetic (AFM) state, the so-called
hedgehog spin-vortex crystal (SVC), and superconductivity (SC) is evidenced by
$^{75}$As nuclear magnetic resonance study on single-crystalline
CaK(Fe$_{0.951}$Ni$_{0.049}$)$_4$As$_4$. The hedgehog SVC order is clearly
demonstrated by the direct observation of the internal magnetic induction along
the $c$ axis at the As1 site (close to K) and a zero net internal magnetic
induction at the As2 site (close to Ca) below an AFM ordering temperature
$T_{\rm N}$ $\sim$ 52 K. The nuclear spin-lattice relaxation rate 1/$T_1$ shows
a distinct decrease below $T_{\rm c}$ $\sim$ 10 K, providing also unambiguous
evidence for the microscopic coexistence. Furthermore, based on the analysis of
the 1/$T_1$ data, the hedgehog SVC-type spin correlations are found to be
enhanced below $T$ $\sim$ 150 K in the paramagnetic state. These results
indicate the hedgehog SVC-type spin correlations play an important role for the
appearance of SC in the new magnetic superconductor.

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The categories of this paper are: physics
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The categories of this paper are: cs
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The categories of this paper are: math-ph
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The categories of this paper are: patt-sol
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The categories of this paper are: econ
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The categories of this paper are: astro-ph
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The categories of this paper are: acc-phys
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The categories of this paper are: chem-ph
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The categories of this paper are: gr-qc
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The categories of this paper are: stat
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The categories of this paper are: nlin
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The categories of this paper are: hep-ph
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The categories of this paper are: hep-lat
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The categories of this paper are: alg-geom
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The categories of this paper are: hep-th
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The categories of this paper are: comp-gas