Nuclear magnetic resonance studies of thallium in a superconducting phase of the Tl-Ba-Ca-Cu-O system

Abstract

Nuclear magnetic resonance measurements of ²⁰³Tl and ²⁰⁵Tl nuclei have been performed in a nearly single phase sample Tl₂Ba₂Ca₂Cu₃O₁₀ both in the normal as well as in the superconducting phase. The resonance shift δ ( =+ 0.30) is small and largely temperature independent above and below the superconducting transition temperature (T_c = 104K, measured inductively). The smallness of the shift sugg- ests that the Tl-derived s-band is filled completely. The magnitude of the relaxation time T₁, that has been measured as a function of temperature, strongly suggests a low density of states at the Fermi level. T₁ is substantially large in the superconducting state as compared to that in the normal state.