Surface impedance of a thin superconducting film in a parallel magnetic field

The problem of the surface microwave impedance of a superconducting film in a static magnetic field H parallel to the surface is considered. In films of thickness d < lambda (lambda is the London penetration depth) the mixed state for a parallel orientation of the external field is a set of vortex r ows, the number of which varies in a discrete manner at certain characteris tic values H-c1((N))(d) of the magnetic field (H-c1((N))(d) is the insertio n field for the Nth vortex row). The surface impedance of the film in the f ield of a normally incident microwave field is calculated with allowance fo r the contribution of oscillating vortex rows. The results obtained in the known theoretical models (Coffey-Clem and Brandt) for the surface impedance of superconductors in the mixed state are generalized to the case of thin films, for which size effects play an important role in the structure and d ynamics of the vortex lattice. (C) 2001 American Institute of Physics.