Infrared study of crystal-field excitations in Nd2-xCexCuO4

Infrared active crystal-field excitations were detected in Nd2-xCexCuO4 sin gle crystals for various x. They correspond to the I-4(9/2)-->I-4(11/2), I- 4(9/2)-->I-4(13/2) and I-4(9/2)-->I-4(15/2) intermultiplet transitions asso ciated with the Nd3+ ion inequivalent sites. Two sets of crystal-field para meters which describe the observed energy spectra were derived. In addition to unperturbed sites, similar to those observed in Nd2CuO4, perturbed site s affected by cerium doping and compatible with available local structure d eformation data are detected. We infer from our data that the Kramers doubl ets of Nd3+ are split and consequently that the antiferromagnetism in the C uO2 planes persists in regions where the unperturbed sites are located, eve n with 7.5% cerium doping.