Observation of Nuclear Resonance of Cu in Pb2Sr2Y1-xCaxCu3O8+δ with x=0 and 0.5

Nuclear resonance of Cu in Pb 2 Sr 2 Y 1- x Ca x Cu 3 O 8+δ with x =0 and 0.5 has been observed under zero external magnetic field. For the nonsuperconducting sample ( x =0), we have observed both the nuclear quadrupole resonance (NQR) and the antiferromagnetic nuclear resonance (AFNR), each of which is due to two inequivalent Cu sites. On the other hand, two sets of NQR signals were observed in the superconducting sample ( x =0.5), indicating the disappearance of antiferromagnetic ordering. The temperature dependence of the nuclear spin-lattice relaxation rate, 1/ T 1 , for the NQR signal in the superconducting sample is also reported.