Spectral origin of the colossal magnetodielectric effect in multiferroic   DyMn2O5
  The origin of the colossal magnetodielectric effect in DyMn2O5 [1] has been an outstanding question in multiferroics. Here, we report the activation of the electric dipole mode at 4-5 cm-1 in an applied magnetic field which fully accounts for the CMD effect. We examine two alternative explanations of this mode: an electromagnon and transitions between f-electron levels of Dy3+ ions. The experimental and theoretical evidence supports the electromagnon origin of the CMD effect. 
A. B. Sushkov and Ch. Kant and M. Schiebl and A. M. Shuvaev and Anna   Pimenov and Andrei Pimenov and B. Lorenz and S. Park ...
cond-mat.str-el