Neutron measurements on an epitaxial thin film of YBaCuO

We report evidence for an ordered flux line lattice in a 2-μm epitaxial film of YBaCuO from both neutron depolarization and diffraction measurements. Depolarization occurred when field cooling was done normal to the film plane but not within it; this is consistent with frozen-in vortices. Evidence for ordering of the flux lines comes from intensity maxima observed in difference patterns between field cooled and zero field cooled conditions.