Magnetically modulated microwave-absorption measurement of the penetration depth in a polycrystalline YBa₂Cu₃O₇_-_x thin-film

• Online Access: http://hdl.handle.net/2047/d20002245

In previous work, a magnetically modulated microwave absorption (MMMA) technique to measure the Ginzburg-Landau parameter κ = (λ/ζ) in high-Tc superconductors (bulk samples of YBCO) was described. In this work, how this technique can be applied to the measurement of the London penetration depth λis described. Data are reported for the temperature variation of λ in a well-characterized c-axis-oriented polycrystalline thin film of YBa₂Cu₃O₇_-_x, prepared by a pulsed laser deposition technique. For low temperatures, λ(O) ≃3640 Å with the microwave electric field oriented parallel to the c axis. The temperature dependence of λ(0)/λ(T) can be well described by the two-fluid model. The data are also reasonably fit by a BCS model, however the MMMA technique (in the work here reported) does not have the resolution at low temperatures to obtain strong quantitative evidence for an energy gap Δ (even if it exists).