Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Electronic structure of spin frustrated magnets: Mn$_3$O$_4$ spinel and
  postspinel   Mn$_3$O$_4$ is a spin frustrated magnet that adopts a tetragonally distorted
spinel structure at ambient conditions and a CaMn$_2$O$_4$-type postspinel
structure at high pressure. We conducted both optical measurements and
\emph{ab} \emph{initio} calculations, and systematically studied the electronic
band structures of both the spinel and postspinel Mn$_3$O$_4$ phases. For both
phases, theoretical electronic structures are consistent with the optical
absorption spectra, and display characteristic band-splitting of the conduction
band. The band gap obtained from the absorption spectra is 1.91(6) eV for the
spinel phase, and 0.94(2) eV for the postspinel phase. Both phases are
charge-transfer type insulators. The Mn 3\emph{d} $t_2$$_g$ and O 2\emph{p}
form antibonding orbitals situated at the conduction band with higher energy.

15
The categories of this paper are: nucl-ex
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The categories of this paper are: chao-dyn
12
The categories of this paper are: nucl-th
2
The categories of this paper are: math
35
The categories of this paper are: mtrl-th
6
The categories of this paper are: astro-ph
33
The categories of this paper are: plasm-ph
29
The categories of this paper are: funct-an
9
The categories of this paper are: nlin
31
The categories of this paper are: ao-sci
25
The categories of this paper are: patt-sol
26
The categories of this paper are: bayes-an
14
The categories of this paper are: math-ph
10
The categories of this paper are: q-bio
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The categories of this paper are: hep-lat
13
The categories of this paper are: quant-ph