Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Manipulating Mn--Mg$_k$ cation complexes to control the charge- and
  spin-state of Mn in GaN   Owing to the variety of possible charge and spin states and to the different
ways of coupling to the environment, paramagnetic centres in wide band-gap
semiconductors and insulators exhibit a strikingly rich spectrum of properties
and functionalities, exploited in commercial light emitters and proposed for
applications in quantum information. Here we demonstrate, by combining
synchrotron techniques with magnetic, optical and \emph{ab initio} studies,
that the codoping of GaN:Mn with Mg allows to control the Mn$^{n+}$ charge and
spin state in the range $3\le n\le 5$ and $2\ge S\ge 1$. According to our
results, this outstanding degree of tunability arises from the formation of
hitherto concealed cation complexes Mn-Mg$_k$, where the number of ligands $k$
is pre-defined by fabrication conditions. The properties of these complexes
allow to extend towards the infrared the already remarkable optical
capabilities of nitrides, open to solotronics functionalities, and generally
represent a fresh perspective for magnetic semiconductors.

30
The categories of this paper are: q-alg
7
The categories of this paper are: hep-th
37
The categories of this paper are: supr-con
31
The categories of this paper are: ao-sci
9
The categories of this paper are: nlin
20
The categories of this paper are: acc-phys
10
The categories of this paper are: q-bio
12
The categories of this paper are: nucl-th
3
The categories of this paper are: physics
11
The categories of this paper are: hep-lat
18
The categories of this paper are: econ
28
The categories of this paper are: alg-geom
29
The categories of this paper are: funct-an
14
The categories of this paper are: math-ph
27
The categories of this paper are: comp-gas
32
The categories of this paper are: atom-ph