EPR and nmr measurements on high-temperature superconductors

Abstract

Some EPR and NMR experiments at the Cu sites in the mixed-phase materials Ba0.6Y0.4CuOy and Ba0.2Y0.8CuOy, and the pure-phase compounds YBa2Cu3Oy (1:2:3), BaCuO2 (0:1:1), Y2Cu2O5 (2:0:2), Y2BaCuO8 (2:1:1), YBa3Cu2Oy (1:3:2) and CuO are presented and discussed. In particular, it is shown that any EPR signal in nominally pure 1:2:3 superconducting material is probably due to a small amount of impurity 2:1:1 (greenphase) compound. For the 2:1:1 and 1:3:2 compounds the authors find g/sub /// approximately=2.23 and gperpendicular to approximately=2.09 with a linewidth of approximately=0.025 T, whereas for the 2:0:2 compound g=2.12(2) with a linewidth of 0.047(3)T. Some suggestions are also made c..