Electron Spin-Lattice Relaxation of Er3+ ions in Er0.01Y0.99Ba2Cu3Ox
  The temperature dependence of the electron spin-lattice relaxation SLR was studied in Er0.01Y0.99Ba2Cu3Ox compounds. The data derived from the electron spin resonance ESR and SLR measurements were compared to those from inelastic neutron scattering studies. SLR of Er3+ ions in the temperature range from 20 K to 65 K can be explained by the resonant phonon relaxation process with the involvement of the lowest excited crystalline-electric-field electronic states of Er3+. These results are consistent with a local phase separation effects. Possible mechanisms of the ESR line broadening at lower temperatures are discussed. Keywords: YBCO; EPR; ESR; Electron spin-lattice relaxation time, T ; Crystalline-electric-field 
V.A. Ivanshin, M.R. Gafurov, I.N. Kurkin, S.P. Kurzin, A. Shengelaya,   H. Keller, M. Gutmann