Penetration depth measurements in epitaxial YBCO thin films by the ESR technique.

Abstract

The electron spin resonance (ESR) technique has been used to obtain the Microwave (mw) penetration depth of YBa2Cu3O7 thin films. An ESR-signal-generating marker was placed in between two high temperature superconducting (HTSC) films' to probe the mw field penetrating through the films. Below the superconducting transition temperature (Tc) the HTSC film started to screen the marker inside the sandwich. A meaningfully diminishing ESR signal was reproducibly recorded for various samples with different markers such as paramagnetic diphenyl pierylhydrazy (DPPH), Mn++ impurity in MgO and a Ferromagnetic (FM) permalloy film Temperature dependence of ESR signal intensity above and below Te has been studied to deduce the penetration depth from the measured signal intensity. A very rapid change of lambda just below Tc, slowed down later at lower temperatures and became smoothly changing. A lambda(ab) = 1020 Angstrom value has been measured for c-axis films at 77K.