Multiferroic behavior in CdCr2X4 (X = S, Se)
  The recently discovered multiferroic material CdCr2S4 shows a coexistence of ferromagnetism and relaxor ferroelectricity together with a colossal magnetocapacitive effect. The complex dielectric permittivity of this compound and of the structurally related CdCr2Se4 was studied by means of broadband dielectric spectroscopy using different electrode materials. The observed magnetocapacitive coupling at the magnetic transition is driven by enormous changes of the relaxation dynamics induced by the development of magnetic order. 
J. Hemberger, P. Lunkenheimer, R. Fichtl, S. Weber, V. Tsurkan, A.   Loidl