Relation between structural instabilities in EuTiO3 and SrTiO3

Specific heat measurements and theoretical calculations reveal an intimate analogy between EuTiO3 and SrTiO3. For EuTiO3, a hitherto unknown specific heat anomaly is discovered at temperatures T-A = 282(1) K, which is analogous to the well-known specific heat anomaly of SrTiO3 at the temperature T-A = 105K caused by an antiferrodistortive transition. Because the zone center soft phonon mode observed in both systems can be modeled with the same parameters, we ascribe the new 282(1) K instability of EuTiO3 to an antiferrodistortive phase transition. The higher transition temperature of EuTiO3 as compared to SrTiO3 results from spin-phonon coupling.