It was demonstrated theoretically that O-doped Ge crystals exhibited non-trivial shallow maxima in their dielectric susceptibilities at 1K. This anomaly originated from the dipolar interaction of rotating Ge2O units randomly distributed in Ge:O samples. Also noted was a similarity between the resultant susceptibility of Ge:O and that observed experimentally for mixed crystals: KCl:Li.

Dielectric Response of Interacting Oxygen Defects in Germanium. H.Shima, T.Nakayama: Physica Status Solidi C, 2004, 1[11], 2933-6