EPR of rare-earth ion clusters in mixed crystals Ba1−x La x F2+x doped with Yb3+ Ion

Electron paramagnetic resonance (EPR) spectra of Yb3+ ions in the mixed crystals (BaF2)1−x X(LaF3) x withx≈0.01 have been investigated by the electron spin echo method at a frequency of 94.9 GHz and compared with the spectra obtained by the continuous-wave EPR at a frequency of 9.5 GHz. Some spectral lines were identified within the framework of the simple cluster model proposed in our previous work (L. K. Aminov, R. Yu. Abdulsabirov, M. R. Gafurov, S. L. Korableva, I. N. Kurkin, S. P. Kurzin, R. M. Rakhmatullin, A. G. Ziganshin: Appl. Magn. Reson. 28, 41–53, 2005). Clusters consist of trigonal dipoles La−F and Yb−F (a rare-earth ion with a charge compensator) and are formed beginning with small concentrationsx≈0.001. The lines identified in the present work were attributed to the clusters with configurations Yb−F−La−F and La−F−Yb−F−La−F.