Ferroelectric phase transition in multiferroic Ge Mn Te driven by local lattice distortions.

The evolution of local ferroelectric lattice distortions in multiferroic Ge Mn Te is studied by x-ray diffraction, x-ray absorption spectroscopy and density functional theory. We show that the anion/cation displacements smoothly decrease with increasing Mn content, thereby reducing the ferroelectric transition from 700 to 100 K at = 0.5, where the ferromagnetic Curie temperature reaches its maximum. First principles calculations explain this quenching by different local bond contributions of the Mn 3 shell compared to the Ge 4 shell in excellent quantitative agreement with the experiments.