Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: One-Dimensional Alignment of Nanoparticles Via Magnetic Sorting   Near room temperature, thin films of MnAs spontaneously align into two
phases, one ferromagnetic and the other paramagnetic. These two phases take the
intriguing form of nanoscale "wires." In this experiment, we investigate the
spontaneous formation of ordered linear arrays of magnetite nanoparticles on
MnAs thin films using scanning probe microscopy.

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The categories of this paper are: hep-th
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The categories of this paper are: solv-int
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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-th
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The categories of this paper are: patt-sol
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The categories of this paper are: dg-ga
32
The categories of this paper are: atom-ph
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The categories of this paper are: q-alg
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The categories of this paper are: cs
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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: chem-ph
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The categories of this paper are: nucl-ex
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The categories of this paper are: q-fin
0
The categories of this paper are: hep-ph