Nuclear spin-lattice relaxation of 139La in (La1−xSrx)2CuO4

We report here the data of 139 La nuclear spin-lattice relaxation times T 1 taken from 4.2K to 275K in (La 1−x Sr x ) 2 CuO 4 , concentrating on a region from x =0.075 (superconducting with highest T c to x =0.15 (metallic). In the superconducting state of the compounds with x =0.075 and 0.10, T 1 −1 just below T c decreases rapidly without any enhancement. In the metallic sample of x =0.15, T 1 follows a Korringa law within our experimental range of 4.2-77K. On the other hand, in the normal state for x =0.075, T 1 −1 shows anomalous increase from 70K to ~150K and then levels off at high temperatures. This anomalous behavior is considered to be originated in a change of the density of state at the Fermi level near to the La sites, probably caused by the orthorhombic-to-tetragonal phase transition.