Magnetoelastic effects and the magnetic phase diagram of multiferroic Dy Mn2 O5

The magnetoelastic coupling in multiferroic Dy Mn2 O5 is investigated by magnetostriction measurements along the three crystallographic orientations. Strong lattice anomalies as a function of the magnetic field are detected at the low temperature magnetic and ferroelectric phase transitions. The sign and magnitude of the magnetostrictive coefficient as well as the lattice anomalies at the transitions are correlated with the Dy moment order and with the sharp changes of the dielectric constant and the ferroelectric polarization. With the magnetic field applied along the c axis a high-field phase has been detected the magnetic structure of which has yet to be explored.