EPR study of some rare-earth ions (Dy3+, Tb3+, and Nd3+) in YBa2Cu3O6-compound

We investigate the low temperature X-band electron paramagnetic resonance (EPR) of YBa(2)Cu(3)O(x) compounds with x congruent with 6.0 doped with Dy(3+), Tb(3+), and Nd(3). The EPR spectra of Dy(3+) and Tb(3+) have been identified. The EPR of Tb(3+) is used also to study the effect of suppression of high T(c) superconductivity by doping with Tb(3+). The EPR of Nd(3+) is probably masked by the intense resonance of Cu(2+). All experimental EPR results compare well with theoretical estimations.