Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Suppression of Superconducting Critical Current Density by Small Flux
  Jumps in $MgB_2$ Thin Films   By doing magnetization measurements during magnetic field sweeps on thin
films of the new superconductor $MgB_2$, it is found that in a low temperature
and low field region small flux jumps are taking place. This effect strongly
suppresses the central magnetization peak leading to reduced nominal
superconducting critical current density at low temperatures. A borderline for
this effect to occur is determined on the field-temperature (H-T) phase
diagram. It is suggested that the small size of the flux jumps in films is due
to the higher density of small defects and the relatively easy thermal
diffusion in thin films in comparison with bulk samples.

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The categories of this paper are: quant-ph
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The categories of this paper are: nucl-th
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The categories of this paper are: math
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The categories of this paper are: alg-geom
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The categories of this paper are: gr-qc
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The categories of this paper are: plasm-ph
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The categories of this paper are: supr-con
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The categories of this paper are: chem-ph
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The categories of this paper are: nucl-ex
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The categories of this paper are: econ
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The categories of this paper are: eess
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The categories of this paper are: bayes-an
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The categories of this paper are: nlin
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The categories of this paper are: mtrl-th
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The categories of this paper are: math-ph
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The categories of this paper are: hep-ex