CU NQR STUDY OF THE SPIN DYNAMICS IN HIGH-TC SUPERCONDUCTOR LA2-XSRXCUO4

The nuclear spin-lattice relaxation time T1 of Cu-63 in La2-xSr(x)CuO4 was measured in the concentration range of x = 0.075 approximately 0.15 near the magnetic phase boundary around x = 0.05. At low Sr concentration and low temperature, (T1T)-1 was found to increase markedly with a development of strong antiferromagnetic (AF) spin correlation among Cu spins. In normal state, (T1T)-1 exhibits a temperature dependence of C/(T + theta) associated with the Curie-Weiss law of the staggered susceptibility chi-Q (T) at the zone boundary, Q = (pi/a, pi/a), above 60 K and approaches a nearly constant value in a narrow T-region just above T(c). T(c) decreases with decreasing theta, becoming zero at x = 0.05 when theta is extrapolated to zero. The rapid decrease of 1/T1 below T(c) has commonly been observed irrespectively of further development of the AF correlation with decreasing Sr content.