Determination of the London penetration depth with EPR of surface spin probes

Abstract Evaluating the temperature dependent line broadening of paramagnetic spins on the surface of superconductors in the model of an ideal vortex state, an upper limit for λ ∥ 4 ) law. The same “two-fluid” behaviour was also found for polycrystalline Bi 2 Sr 1.3 Ca 0.7 CuO 6.15 sample. However, evidence temperature law was observed for c-oriented epitactic Bi- and YBCO thin films. However, evidence for a dominant contribution of magnetic field gradients on a larger scale than the lattice constant of the ideal vortex state was found for the GdBCO system by evaluating EPR line narrowing for a spin probe with fast spin diffusion.