Vortices and surface barriers in a YBa2Cu3O7-x superconducting film

We have studied the magnetic vortices running parallel to the surface of a thin-film YBa2Cu3O7-x superconductor with Spin-Polarized Neutron Reflectivity (SPNR). Unlike other techniques, SPNR can describe only the vortices which place parallel to the film surfaces. With the help of a theoretical model calculation, we could extract the density and distribution of vortices running parallel to the surfaces from the SPNR data. From the SPNR data analysis we found that the vortex entrance to the superconducting film was retarded as applied magnetic field increased while the vortices were trapped for decreasing field. The motion of the vortices could be understood in terms of surface barriers. Understanding vortex-surface interaction would be very valuable for practical appellations as well as academic research of superconductors