MEASUREMENTS OF ANISOTROPIC CHARACTERISTIC LENGTHS IN YBCO FILMS AT MICROWAVE-FREQUENCIES

We used microwave self-resonant and magnetically modulated microwave a bsorption techniques to measure the London penetration depth, lambda, and coherence length, xi, in the direction parallel and perpendicular to the a-b plane of YBCO films. We found that both lambda and xi were anisotropic; it appeared that the value of lambda(parallel-to) (0) was about 1800 angstrom and lambda(perpendicular-to) (86.5) about 26 000 angstrom, where lambda(parallel-to) is the penetration depth for the a pplied microwave electric field parallel and lambda(perpendicular-to) perpendicular to the film plane (c-axis is perpendicular to the film p lane). We deduced xi(parallel-to) to be equal to 129 angstrom and ix(p erpendicular-to) 40 angstrom at 86.5 K. The anisotropy factor y we det ermined to be about 3.