Structural anomalies at the magnetic and ferroelectric transitions in RMn2O5 (R=Tb,Dy,Ho)

Strong anomalies of the thermal expansion coefficients at the magnetic and ferroelectric transitions have been detected in multiferroic RMn2O5. Their correlation with anomalies of the specific heat and the dielectric constant is discussed. The results provide evidence for the magnetic origin of the ferroelectricity mediated by strong spin-lattice coupling in the compounds. Neutron scattering data for HoMn2O5 indicate a spin reorientation at the two low-temperature phase transitions.