Nuclear Quadrupole Resonance of Cu in Superconducting (La_0.925Sr_0.075)₂CuO₄

Abstract

Nuclear quadrupole resonance (NQR) signals of 65 Cu and 63 Cu have been discovered in the high- T c superconducting oxide (La 0.925 Sr 0.075 ) 2 CuO 4 at 33.0 MHz and 35.3 MHz, respectively. The temperature dependence of the nuclear spin-lattice relaxation rate 1/ T 1 was similar to that of Cu(II) (CuO 2 plane) in the YBa 2 Cu 3 O 7-δ system (Y system). From the behavior of 1/ T 1 , it is pointed out that the relaxation arises from the same mechanism as that of the CuO 2 plane in the Y system, where the relaxation in the normal state is considered to be dominated by the spin fluctuations of the nearly localized Cu-3 d holes.