Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Improved critical current densities in MgB2 tapes with ZrB2 doping   MgB2/Fe tapes with 2.5-15 at.% ZrB2 additions were prepared through the in
situ powder-in-tube method. Compared to the pure tape, a significant
improvement in the in-field critical current density Jc was observed, most
notably for 10 at.% doping, while the critical temperature decreased slightly.
At 4.2 K, the transport Jc for the 10 at.% doped sample increased by more than
an order of magnitude than the undoped one in magnetic fields above 9 T.
Nanoscale segregates or defects caused by the ZrB2 additions which act as
effective flux pinning centers are proposed to be the main reason for the
improved Jc field performance.

8
The categories of this paper are: hep-ex
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The categories of this paper are: q-fin
33
The categories of this paper are: plasm-ph
11
The categories of this paper are: hep-lat
31
The categories of this paper are: ao-sci
21
The categories of this paper are: adap-org
15
The categories of this paper are: nucl-ex
36
The categories of this paper are: cmp-lg
25
The categories of this paper are: patt-sol
18
The categories of this paper are: econ
27
The categories of this paper are: comp-gas
34
The categories of this paper are: chem-ph
6
The categories of this paper are: astro-ph
12
The categories of this paper are: nucl-th
26
The categories of this paper are: bayes-an
2
The categories of this paper are: math