Spin susceptibility and doping dependence in Tl0.5Pb0.5Sr2Ca1−xYxCu2O7−δ a round the metal-insulator transition 63,65Cu, 207Pb and 205Tl NMR and spin-lattice relaxation

Abstract NMR line shifts of 63 Cu, 207 Pb and 205 Tl were measured in the cuprates Tl 0.5 Pb 0.5 Sr 2 Ca 1− x Cu 2 O 7 ( x = 0.0–1.0) in order to investigate the evolution of the spin susceptibility χ S around the metal-insulator transition, which occurs when the yttrium content increases up to x ≌ 0.6. The Knight shift was evaluated for 63 Cu, 207 Pb and 205 Tl and the corresponding change of the static spin susceptibility χ S ( q = 0) was determined from the NMR data in the superconducting state. In the superconducting phase, where T c has a maximum at x = 0.2, the value of χ S ( q = 0) increases gradually with hole doping. The 63 Cu zero-field NMR and the NMR spectra of 207 Pb and 205 Tl for Tl 0.5 Pb 0.5 Sr 2 YCu 2 O 7 reported here present the first NMR observation of antiferromagnetic ordering in these thallium-based cuprates.