The phase diagram of Sr${}_{1-x}$Eu${}_x$TiO${}_3$ is determined experimentally by electron paramagnetic resonance and resistivity measurements and analyzed theoretically within the self-consistent phonon approximation as a function of $x$ (0.03 ⩽ $x$ ⩽ 1.0). The transition temperature of the structural instability of the system increases nonlinearly to higher temperatures with increasing $x$. This is interpreted theoretically by a substantial alteration in the dynamics caused by a change in the double-well potential from broad and shallow to narrow and deep.

• Received 17 January 2012

DOI:https://doi.org/10.1103/PhysRevB.85.134113