Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Vortex lock-in transition coinciding with the 3D to 2D crossover in
  YBa2Cu3O7   A vortex lock-in transition was directly detected by torque magnetometry in
an overdoped YBa2Cu3O7 single crystal of low anisotropy (\approx 7). The
locked-in state was observed below the 3D to 2D crossover temperature Tcr = 76
K, independently of extrinsic pinning effects thanks to a high quality clean
crystal and the use of a vortex shaking technique. The shape of the torque
signal as a function of the angle between the applied magnetic field and the
crystallographic c-axis is in very good agreement with the model developped by
Feinberg and Ettouhami [Int. J. Mod. Phys. B 7, 2085 (1993)] for quasi-2D
superconductors, despite the low anisotropy of the material.

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The categories of this paper are: hep-ph
33
The categories of this paper are: plasm-ph
15
The categories of this paper are: nucl-ex
24
The categories of this paper are: dg-ga
23
The categories of this paper are: solv-int
12
The categories of this paper are: nucl-th
34
The categories of this paper are: chem-ph
26
The categories of this paper are: bayes-an
28
The categories of this paper are: alg-geom
27
The categories of this paper are: comp-gas
31
The categories of this paper are: ao-sci
11
The categories of this paper are: hep-lat
6
The categories of this paper are: astro-ph
22
The categories of this paper are: chao-dyn
14
The categories of this paper are: math-ph
5
The categories of this paper are: gr-qc