Abstract
NMR spectra and spin-lattice relaxation in the normal and superconducting states were measured on an aligned sample of . The spin-lattice relaxation time, , was found to be isotropic and, in the normal state, 1/T to be temperature dependent, indicating the presence of spin fluctuations in the thallium-oxygen plane similar to that found in the copper-oxygen plane of . $ sup 205—Tl NMR spectra at 5 K were studied and the angular dependence of the field shift at the saddle points of the magnetic-field distribution was found to be consistent with the anisotropic London theory. The average penetration depth was inferred to be 7040±350 Å. Our approach to determine the penetration depth, the saddle-point field analysis, is insensitive to distortion of the flux lattice associated with pinning. This is in contrast to the more commonly used second-moment method.
- Received 6 September 1991
DOI:https://doi.org/10.1103/PhysRevB.45.4945
©1992 American Physical Society