Determination of the magnetic field penetration depth in YBa2Cu3O7 superconducting films by polarized neutron reflectometry

Polarized neutron reflectometry was used for the direct measurement of the magnetic-field penetration depth in a high-temperature (HTc) superconducting film. Two scattering geometries were used. The deduced neutron scattering length density profile gave an exact picture of the composition of the film. The fit to the spin-asymmetry yielded a magnetic-penetration depth of 1400±100 A at a temperature of T=4.8 K along the c-axis oriented perpendicular to the film surface. The model included an intrinsic exponential decay of the penetration depth. For the first time the spin-asymmetry was determined with high resolution over an extended Q-range for a HTc-film. Nb-films were investigated as reference. (orig.)