Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Second Homologous Series of Iron Pnictide Oxide Superconductors
  (Fe2As2)(Can+2(Al,Ti)nOy)[n = 2,3,4]   We have discovered a new homologous series of iron pnictide oxides
(Fe2As2)(Can+2(Al,Ti)nOy)[n = 2,3,4]. These compounds have perovskite-like
blocking layers between Fe2As2 layers. The structure of new compounds are
tetragonal with space groups of P4/nmm for n = 2 and 4 and P4mm for n = 3,
which are similar to those of (Fe2As2)(Can+1(Sc,Ti)nOy)[n = 3,4,5] found in our
previous study. Compounds with n = 3 and 4 have new crystal structures with 3
and 4 sheets of perovskite layers, respectively, including a rock salt layer in
each blocking layer. The a-axis lengths of the three compounds are
approximately 3.8 A, which are close to those of FeSe and LiFeAs.
(Fe2As2)(Ca6(Al,Ti)4Oy) exhibited bulk superconductivity in magnetization
measurement with Tc(onset)~36 K and resistivity drop was observed at ~39 K.
(Fe2As2)(Ca5(Al,Ti)3Oy) also showed large diamagnetism at low temperatures.
These new compounds indicate considerable rooms are still remaining for new
superconductors in layered iron pnictides.

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The categories of this paper are: hep-lat
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The categories of this paper are: plasm-ph
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The categories of this paper are: hep-ex
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The categories of this paper are: hep-ph
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The categories of this paper are: cs
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The categories of this paper are: nlin
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The categories of this paper are: math
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The categories of this paper are: q-alg
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The categories of this paper are: q-fin
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The categories of this paper are: gr-qc
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The categories of this paper are: econ
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The categories of this paper are: funct-an
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The categories of this paper are: eess
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The categories of this paper are: chao-dyn
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The categories of this paper are: acc-phys
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The categories of this paper are: supr-con