63Cu NMR Study of Spin Dynamics in La2-x(Sr, Ba)xCuOy (0.04≤x≤0.16, 3.99≤y≤4.03)

The 63 Cu nuclear spin-lattice relaxation rate 1/ T 1 has been measured for oriented powders of La 2- x (Sr, Ba) x CuO y in a wide concentration range. The spin dynamics in a lightly doped nonsuperconductor, La 1.96 Sr 0.04 CuO 4.02 , is found to be qualitatively similar to that of a moderately doped high T c superconductor, La 1.85 Sr 0.15 CuO 4.03 . The antiferromagnetic correlation length in the latter is estimated to be reduced by a factor of ∼2. The normal state spin dynamics has been successfully observed down to liquid helium temperature for La 1.88 Ba 0.12 CuO 4.00 . The result showed a monotonous decrease of 1/ T 1 with somewhat sublinear temperature dependence below 100 K.