Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Co atoms on Bi$_{2}$Se$_{3}$ revealing a coverage dependent spin
  reorientation transition   We investigate Co nanostructures on Bi$_{2}$Se$_{3}$ by means of scanning
tunneling microscopy and spectroscopy [STM/STS], X-ray absorption spectroscopy
[XAS], X-ray magnetic dichroism [XMCD] and calculations using the density
functional theory [DFT]. In the single adatom regime we find two different
adsorption sites by STM. Our calculations reveal these to be the fcc and hcp
hollow sites of the substrate. STS shows a pronounced peak for only one species
of the Co adatoms indicating different electronic properties of both types.
These are explained on the basis of our DFT calculations by different
hybridizations with the substrate. Using XMCD we find a coverage dependent spin
reorientation transition from easy-plane toward out-of-plane. We suggest
clustering to be the predominant cause for this observation.

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The categories of this paper are: astro-ph
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The categories of this paper are: hep-ph
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The categories of this paper are: gr-qc
34
The categories of this paper are: chem-ph
21
The categories of this paper are: adap-org
3
The categories of this paper are: physics
27
The categories of this paper are: comp-gas
30
The categories of this paper are: q-alg
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The categories of this paper are: hep-ex
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The categories of this paper are: stat
28
The categories of this paper are: alg-geom
31
The categories of this paper are: ao-sci
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The categories of this paper are: math
29
The categories of this paper are: funct-an
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The categories of this paper are: cs
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The categories of this paper are: quant-ph