Tuning the structural instability of SrTiO_3 by Eu doping: The phase   diagram of Sr_1-xEu_xTiO_3
  The phase diagram of Sr_1-xEu_xTiO_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 ([0.03-1.0]). 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. 
Z. Guguchia, A. Shengelaya, H. Keller, J. K\"ohler, and A.   Bussmann-Holder
cond-mat.mtrl-sci