Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Vortex Structure and Anisotropic Superconducting Gaps in
  Ba[Fe(Ni)]$_2$As$_2$   We studied nearly optimally Ni-substituted BaFe$_{2-x}$Ni$_x$As$_2$ (BFNA)
single crystals with $T_C \approx 18.5$\,K. In irreversible magnetization
measurements, we determined the field dependence of the critical-current
density and discuss the nature of observed strong bulk pinning. Using intrinsic
multiple Andreev reflections effect (IMARE) spectroscopy, we directly determine
two distinct superconducting gaps and resolve their moderate anisotropy in the
momentum space. The BCS-ratio for the large gap $2\Delta_L/k_BT_C > 4.1$
evidences for a strong coupling in the $\Delta_L$-bands.

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The categories of this paper are: hep-th
24
The categories of this paper are: dg-ga
16
The categories of this paper are: stat
31
The categories of this paper are: ao-sci
15
The categories of this paper are: nucl-ex
2
The categories of this paper are: math
1
The categories of this paper are: cs
5
The categories of this paper are: gr-qc
11
The categories of this paper are: hep-lat
36
The categories of this paper are: cmp-lg
37
The categories of this paper are: supr-con
33
The categories of this paper are: plasm-ph
20
The categories of this paper are: acc-phys
32
The categories of this paper are: atom-ph
35
The categories of this paper are: mtrl-th
19
The categories of this paper are: eess