Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Antiferromagnetism in the Vortex Cores of YBa$_2$Cu$_3$O$_{7-\delta}$   We report spatially resolved nuclear magnetic resonance measurements on a
high temperature superconductor that indicate the presence of correlated
antiferromagnetic fluctuations in the vortex core. The nuclear spin-lattice
relaxation rate, $1/^{17}T_1$, of planar $^{17}O$, in near-optimally doped
YB$_2$Cu$_3$O$_{7-\delta}$ (YBCO), was measured. Outside of the core,
$(^{17}T_1T)^{-1}$ is independent of temperature consistent with theoretical
predictions for a {\it d}-wave superconductor. In the vortex core
$(^{17}T_1T)^{-1}$ increases with decreasing temperature following an
antiferromagnetic Curie-Weiss law.

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The categories of this paper are: comp-gas
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The categories of this paper are: eess
24
The categories of this paper are: dg-ga
6
The categories of this paper are: astro-ph
34
The categories of this paper are: chem-ph
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The categories of this paper are: atom-ph
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The categories of this paper are: acc-phys
5
The categories of this paper are: gr-qc
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The categories of this paper are: funct-an
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The categories of this paper are: solv-int
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The categories of this paper are: hep-ex
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The categories of this paper are: nucl-ex
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The categories of this paper are: bayes-an
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The categories of this paper are: supr-con
1
The categories of this paper are: cs
35
The categories of this paper are: mtrl-th