Magnetic and electronic properties of YBa 2Cu 3O x (6.5 < x < 7.0) studied by muon spin rotation

Abstract

A systematic study of the local magnetic field distribution p( B) in the perovskite-type superconductor YBa 2Cu 3O x is presented. Special attention is given to the second moment 〈 ΔB 2 〉 of p( B) which is closely related to the superconducting carrier density n s and the effective mass m ∗ of the superconducting carriers. The influence of temperature, anisotropy and hole doping are investigated in detail. It is found that the temperature dependence of the magnetic penetration depth in YBa 2Cu 3O x is in agreement with conventional s-wave pairing and suggests strong coupling. The anisotropic behavior of p( B) is well described by a theory for uniaxial type II superconductors, with an anisotropy ratio γ ∼- 5(1). Moreover, the zero-temperature values λ ab (0) = 130(10) nm and λ c (0) ∼- 500–800 nm (penetration depth for screening currents flowing in the ab-planes and along the c-axis, respectively) were extracted from our data. μSR experiments performed on oxygen deficient samples indicate that the structural and electronic properties of YBa 2Cu 3O x are strongly correlated via the oxygen content x.