Nuclear Spin-Lattice Relaxation of63,65Cu at the Cu(2) Sites of the HighTcSuperconductor YBa2Cu3O7-δ

Abstract

Nuclear spin-lattice relaxation times T ₁ of ⁶³ Cu and ⁶⁵ Cu in the Cu(2) sites of the high T _c superconductor YBa ₂ Cu ₃ O _7-δ (δ≃0.1, T _c =91 K) have been measured for the wide temperature range between 2.2 K and 300 K. The temperature dependence of 1/ T ₁ in the normal state has been found to be the one unexpected for simple metals. The influences of antiferromagnetic spin fluctuations in the d–p bands in the Cu(2)–O layers are discussed. The temperature dependence of 1/ T ₁ below T _c has also been found to be the one which is not expected for isotropic BCS superconductors. The power-law like temperature dependence of 1/ T ₁ without any enhancement just below T _c has been observed between 40 K and 91 K.