Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Demonstration of defect-defect ferromagnetic coupling in Gd doped GaN
  epitaxial films: A polarization selective magneto-photoluminescence study   Magnetic field dependent polarization selective photoluminescence(PL) study
has been carried out at 1.5~K on Gd-doped GaN epitaxial layers grown on c-SiC
substrates by molecular beam epitaxy technique. It has been found that the
incorporation of Gd in GaN leads to the generation of three types of donor like
defects that result in neutral donor bound excitonic features in low
temperature PL. The study reveals that the rate of spin-flip scattering for all
the three excitonic features becomes almost $B$-independent suggesting that
these signals must be stemming from defects which are ferromagnetically coupled
with each other. This is further confirmed by the study carried out on a GaN
sample co-doped with Si and Gd, where defects are found to be ferromagnetically
coupled, while Si-donors do not show any involvement in coupling.

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The categories of this paper are: mtrl-th
18
The categories of this paper are: econ
31
The categories of this paper are: ao-sci
36
The categories of this paper are: cmp-lg
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The categories of this paper are: funct-an
12
The categories of this paper are: nucl-th
2
The categories of this paper are: math
1
The categories of this paper are: cs
37
The categories of this paper are: supr-con
32
The categories of this paper are: atom-ph
10
The categories of this paper are: q-bio
11
The categories of this paper are: hep-lat
14
The categories of this paper are: math-ph
19
The categories of this paper are: eess
16
The categories of this paper are: stat
17
The categories of this paper are: q-fin