Magnetic penetration depth and flux-pinning effects in high-Tc superconductor La1.85Sr0.15CuO

Abstract

We have performed muon-spin-relaxation (μSR) measurements on ${\mathrm{La}}_{1.85}$ ${\mathrm{Sr}}_{0.15}$ ${\mathrm{CuO}}_4$ above and below its superconducting transition temperature, $T_c$=37 K. From transverse-field μSR at 6 K, the magnetic penetration depth is λ≊2500 Å, which, together with previous thermodynamic data and the London formula, implies a carrier density of 0.3×${10}^{22}$ ${\mathrm{cm}}^{\mathrm{-}3}$. The temperature dependence of λ in our sintered powder sample differs from that for an ordinary homogeneous superconductor. We also show that the longitudinal- and transverse-field μSR techniques are sensitive probes of $H_{c1}$ and flux-pinning effects.