Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Electronic structure of YbFe$_4$Al$_8$ antiferromagnet: A combined X-ray
  photoelectron spectroscopy and first-principles study   Depending on their chemical composition, Yb compounds often exhibit different
valence states. Here we investigate the valence state of YbFe$_4$Al$_8$ using
X-ray photoelectron spectroscopy (XPS) and first-principles calculaions. The
XPS valence band of YbFe$_4$Al$_8$ consists of two contributions coming from
divalent (Yb$^{2+}$) and trivalent (Yb$^{3+}$) configurations. The determined
value of the valence at room temperature is 2.81. Divalent and trivalent
contributions are also observed for core-level Yb 4$d$ XPS spectra. We study
several collinear antiferromagnetic models of YbFe$_4$Al$_8$ from the
first-principles and for comparison we also consider LuFe$_4$Al$_8$ with a
fully filled 4$f$ shell. We predict that only Fe sublattices of YbFe$_4$Al$_8$
carry significant magnetic moments and that the most stable magnetic
configuration is AFM-C with antiparallel columns of magnetic moments. We also
present a Mullliken electronic population analysis describing charge transfer
both within and between atoms. In addition, we also study the effect of
intra-atomic Coulomb U repulsion term applied for 4$f$ orbitals on Yb valence
and Fe magnetic moments.

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The categories of this paper are: dg-ga
6
The categories of this paper are: astro-ph
2
The categories of this paper are: math
1
The categories of this paper are: cs
12
The categories of this paper are: nucl-th
8
The categories of this paper are: hep-ex
16
The categories of this paper are: stat
37
The categories of this paper are: supr-con
7
The categories of this paper are: hep-th
0
The categories of this paper are: hep-ph
9
The categories of this paper are: nlin
13
The categories of this paper are: quant-ph
18
The categories of this paper are: econ
22
The categories of this paper are: chao-dyn
27
The categories of this paper are: comp-gas
10
The categories of this paper are: q-bio