Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Controlled aggregation of magnetic ions in a semiconductor. Experimental
  demonstration   The control on the distribution of magnetic ions into a semiconducting host
is crucial for the functionality of magnetically doped semiconductors. Through
a structural analysis at the nanoscale, we give experimental evidence that the
aggregation of Fe ions in (Ga,Fe)N and consequently the magnetic response of
the material are affected by growth rate and co-doping with shallow impurities.

27
The categories of this paper are: comp-gas
35
The categories of this paper are: mtrl-th
20
The categories of this paper are: acc-phys
5
The categories of this paper are: gr-qc
29
The categories of this paper are: funct-an
17
The categories of this paper are: q-fin
3
The categories of this paper are: physics
11
The categories of this paper are: hep-lat
32
The categories of this paper are: atom-ph
9
The categories of this paper are: nlin
24
The categories of this paper are: dg-ga
14
The categories of this paper are: math-ph
18
The categories of this paper are: econ
33
The categories of this paper are: plasm-ph
31
The categories of this paper are: ao-sci
37
The categories of this paper are: supr-con