AN EPR STUDY OF CU2+ SUBSTITUTION IN LA2NIO4

The vexing problem of the absence of a Cu2+ EPR signal from the antife rromagnetic parent phases of high-T-c cuprate superconductors (e.g. La 2CuO4) is addressed. EPR measurements were carried out on the series L a2Ni1-xCuxO4 (x = 0.00-1.00) where it is perceived that Cu2+ moments c an be generated in a localised, 'EPR responsive', state, which in prin ciple would facilitate observation of the nature of the spin dynamics on the microscopic scale as a function of Cu2+ concentration. For the whole series no signals intrinsic to the prepared phase were detected, a response that is discussed with reference to currently debated theo retical models.