Indication for a novel phase in the quantum paraelectric regime of SrTiO₃

Electron paramagnetic resonance of Fe3+ gives evidence for a phase-transition-like feature in SrTiO3 below Tq=37±1 K, both in the tetragonal and the pressure-induced trigonal phase. In the latter, Tq shifts to lower temperatures as a function of uniaxial stress p111. The new phenomenon is very tentatively discussed in terms of a possible transition to a novel coherent quantum state. © 1991 Springer-Verlag.