63Cu NMR shift and relaxation behavior in Tl 2Ba 2Ca 2Cu 3O 10−δ ( Tc=125K)

Abstract

Extensive 63Cu NMR measurements have been carried out on a magnetically aligned sample of the triple-layered superconductor Tl 2Ba 2Ca 2Cu 3O 10−δ ( T c=125K). The 63Cu shifts in the three Cu-O layers all have a similar temperature depen dence to that of 17O, showing that they probe the same static spin susceptibility. The magnetic properties of this material were found to resemble those of underdoped YBa 2Cu 3O 7−δ. The Knight shift decreases dramatically with decreasing temperature below 150 K in the normal state, whereas the nuclear spin lattice relaxation rate (1/ T 1 T) shows a broad maximum at ≈ 165 K, indicating an opening of a spin gap well above T c.