Penetration depth from far-infrared transmission in YBa2Cu3O7 thin films

We have deduced the penetration depth λ(T) on YBa2Cu3O7 thin films from transmission measurement in the range 100–550 GHz. Our data yield simultaneously the absolute value and the temperature dependence of λ(T). In lower-quality films, we report a usualT2 dependence, associated to a large value of λ(0) compared to the standard 1400Å value reported in the literature. In better-quality films λ exhibits a linear temperature dependence associated …