Cu Nuclear Spin-Lattice Relaxation Study of A- and B-Sites in La1.80Sr0.20CuO4(Tc=30K)

We report the temperature( T )-dependence of the planar 63 Cu nuclear spin-lattice relaxation rate, 1/ T 1 , both at the Cu(A)-site (77.3 K≤ T ≤500 K) and at the Cu(B)-site (77.3 K≤ T ≤300 K) in the high- T c Cu oxide, La 1.80 Sr 0.20 CuO 4 ( T c ∼30 K), measured by the Cu NQR spin-echo technique. We found that 1/ T 1 at the Cu(B)-site is different from that at the Cu(A)-site, and that 1/ T 1 at the Cu(A)-site has a superlinear T -dependence in the T -range of 300∼500 K. Comparisons of the present 1/ T 1 are made with the data for other systems. The difference in 1/ T 1 between two Cu sites is discussed from the viewpoint of local inhomogeneous electronic states.