Multiple-valued electric polarization in multiferroic GdMn2O5 from first principles

Evidence for an electromagnon in GdMn2O5 : A multiferroic with a large electric polarization

“…We thus propose a purely electronic excitation where orbital and spin degrees of freedom are no longer decoupled. This picture is strongly supported by recent evidence of an electronic contribution to the usual ionic ferroelectricity [51,52] in this family and may explain the exhaustive experimental results reported here. This framework could be relevant not only in the entire family of RMn 2 O 5 but in all magnetoelectric materials.…”

“…This calls into question the very nature of this excitation. As reported recently [50,51], the total electric polarization results from a combination of both an ionic and an electronic component.…”

“…In light of this information, our results strongly suggest that the electromagnon in GdMn 2 O 5 is a purely electronic excitation. In the actual Pm space group, four different ferroelectric ground states are predicted [51] in the magnetic phase, corresponding to the four sign combinations for the a and b components of the polarization. In this picture a change of the magnetic structure modifies the electronic density.…”