Journal of Physical Studies 2(2), 258–262 (1998) DOI: https://doi.org/10.30970/jps.02.258 POLARIZED NEUTRON REFLECTOMETRY STUDIES OF FLUX PENETRATION IN YBa2Cu3O7 SUPERCONDUCTING FILMS

V. Lauter-Pasyuk^{1, 3}, H. J. Lauter², A. V. Petrenko³, V. L. Aksenov³, P. Leiderer^1
1Universität Konstanz Fakultät für Physik, Postfach 5560, D-78434, Konstanz, Germany
²Institut Laue Langevin, B.P.156, F-38042, Grenoble Cedex 9, France
³Joint Institute for Nuclear Research, 141980 Dubna, Moscow Region, Russia

The technique of Polarized Neutron Reflectometry (PNR) was used for the measurement of the magnetic flux penetration in high–temperature (high–$T_{c}$) superconducting thin films. Different superconducting phases of high–$T_{c}$ films were studied, namely the Meissner state ($H < H_{c1}$) and the mixed state ($H_{c1} < H < H_{c2}$). The experiments on high–$T_{c}$ films were made in two scattering geometries: reflection from the ‟vacuum–film" or ‟substrate–film" interface. For the Meissner state the model fit to the experimental data gave a magnetic penetration depth of 1350$\pm$150 \AA \ along the $c$–axis at a temperature of $T$ = 2 K. The c–axis was oriented perpendicular to the film surface. The model included the intrinsic exponential decay of the penetrating flux. In the mixed state the distribution of flux–lines in the high–$T_{c}$ thin film was determined for the first time by PNR in an external magnetic field of 1.5 kOe applied parallel to the film surface.

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