Novel multiferroic state of Eu1-xYxMnO3 in high magnetic fields.

Magnetic and dielectric properties of Eu1-xYxMnO3 (x=0 and 0.4) are studied in pulsed magnetic fields up to 55 T. For x=0, application of magnetic fields higher than 20 T along the b axis causes magnetic transitions accompanied by generation of electric polarization (P) along the a axis. Similar first-order transitions are also observed in crystals of x=0.4, in which the ground state at zero magnetic field is already a ferroelectric P parallel a phase of different origin. Realistic model calculation indicates the presence of a novel multiferroic state induced by the spin exchange striction mechanism in high magnetic fields as an essential nature of the frustrated Mn spin system in this class of manganites.