Magnetic field penetration depth of La1.85Sr0.15CuO4 measured by muon spin relaxation

Abstract

Muon-spin-relaxation measurements have been performed on a high-$T_c$ superconductor (${\mathrm{La}}_{1.85}$ ${\mathrm{Sr}}_{0.15}$)${\mathrm{CuO}}_4$. In an external transverse magnetic field of 500 G, a magnetic field penetration depth λ=2000 Å at T=10 K has been determined from the muon-spin-relaxation rate which increased with decreasing temperature below $T_c$. From this λ and the Pauli susceptibility we estimate the superconducting carrier density to be n=3×${10}^{21}$/${\mathrm{cm}}^3$. The zero-field relaxation rates above and below $T_c$ were equal, which suggests that the superconducting state in this sample is not associated with detectable static magnetic ordering.