Cu Nuclear Spin-Spin Relaxation in Tl2Ba2CuO6+δ

We have measured the temperature ( T ) dependence of the Gaussian decay rate 1/ T G associated with the 63 Cu nuclear spin-spin relaxation of Tl 2 Ba 2 CuO 6+δ ( T c ∼85 K) by the NMR spin-echo technique. 1/ T G increases from T c up to T sp ∼120 K and decreases monotonically in a Curie-Weiss-like law above T sp . In spite of the nonmonotonic T -dependence of (1/ T G ) 2 [∼χ( Q )], we have found that (1/ T G ) 2 scales to 1/ T 1 T and hence 1/ T 1 ∝ T χ( Q ) is valid above T c . This result indicates that the antiferromagnetic spin-fluctuation theory for the two-dimensional itinerant electron system holds for the present overdoped monolayered Cu oxide without a dynamical gap.