EPR of YBa2Cu3O6+y: Models of paramagnetic centers with g ≈ 4.2

A systematic investigation of the EPR line with g ≈ 4.2 in YBa2Cu3O6+y has been carried out. From the temperature dependence of the line integrated intensity we have deduced that the line is due to paramagnetic centers with integer spin. The energy interval between the ground singlet state and the excited state with S = 1 was estimated as 8-10 K. Energy levels of the cluster Cu2+ (S = 1/2)-"Cu3+(S = 0)"-Cu2+(S = 1/2) were calculated for different sets of parameters. © 2000 Elsevier Science B.V. All rights reserved