Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Self doping effect and successive magnetic transitions in
  superconducting Sr$_2$VFeAsO$_3$   We have studied a quinary Fe-based superconductor Sr$_2$VFeAsO$_3$ by the
measurements of x-ray diffraction, x-ray absorption, M\"{o}ssbauer spectrum,
resistivity, magnetization and specific heat. This apparently undoped
oxyarsenide is shown to be self doped via electron transfer from the V$^{3+}$
ions. We observed successive magnetic transitions within the VO$_2$ layers: an
antiferromagnetic transition at 150 K followed by a weak ferromagnetic
transition at 55 K. The spin orderings within the VO$_2$ planes are discussed
based on mixed valence of V$^{3+}$ and V$^{4+}$.

22
The categories of this paper are: chao-dyn
25
The categories of this paper are: patt-sol
15
The categories of this paper are: nucl-ex
28
The categories of this paper are: alg-geom
23
The categories of this paper are: solv-int
21
The categories of this paper are: adap-org
34
The categories of this paper are: chem-ph
8
The categories of this paper are: hep-ex
2
The categories of this paper are: math
7
The categories of this paper are: hep-th
33
The categories of this paper are: plasm-ph
11
The categories of this paper are: hep-lat
35
The categories of this paper are: mtrl-th
17
The categories of this paper are: q-fin
16
The categories of this paper are: stat
9
The categories of this paper are: nlin