Local structure of multiferroic RMn2O5: Important role of the R site

The temperature and magnetic field dependent local structure of RMn2O5 systems was examined. While no significant displacements of the Mn ions are observed, it is found that the R–O distribution exhibits changes at low temperature which are possibly related to the changes in the electric polarization. Density functional computations are used to explore the system dynamics and to link the local structural measurements with anomalous changes in the infrared absorption spectra. The anomalous R–O distribution and observed coupling to magnetic fields point to the need to properly treat the 4f electrons on the R sites in these systems.