The room-temperature structural properties of the RMn 2 O 5 multiferroics have been investigated under pressure, using powder X-ray scattering and density functional theory (DFT) calculations. It was possible to determine the lattice parameters and the main atomic positions as a function of pressure. Good agreement was observed between the X-ray and DFT results for most of the determined crystallographic data. From the DFT calculations, it was possible to infer the pressure evolution of the exchange interactions, and this analysis led to the conclusion that the onset of the q = ( 1 2 , 0, 1 2 ) magnetic structure under pressure is related to the increase in the J 1 super-exchange terms (due to the reduction in the Mn-O distances) compared with the Mn-R exchange interactions. In addition, the 1D antiferromagnetic character of the compounds should be reinforced under pressure.

We report in this paper the dynamical properties of GdMn 2 O 5 studied by inelastic neutron scattering and infrared spectroscopy assisted by ab initio calculations. Our work sheds light on the electromagnon, a magnetic mode that can be excited by an electric field. Combining spin-wave measurements, simulations, and ab initio calculations of the single-ion anisotropies and the superexchange interactions, we describe in detail the magnetic contribution to this mode. An exhaustive study of the temperature and polarization dependence of its electroactivity completes this comprehensive study of the complex GdMn 2 O 5 system.