Photocreating Supercooled Spiral-Spin States in a Multiferroic Manganite
Y. M. Sheu1*, N. Ogawa2, Y. Kaneko2, Y. Tokura2
1Department of Electrophysics, National Chiao Tung University, Hsinchu, Taiwan
2Center for Emergent Matter Science, RIKEN, Wako, Saitama, Japan
* presenting author:Yu-Miin Sheu,
I will demonstrate that dynamics of the ab-spiral-spin order in a magnetoelectric multiferroic Eu0.55Y0.45MnO3 (EYMO) can be unambiguously probed through optical second harmonic signal, generated via the spin-induced ferroelectric polarization. In case of relatively weak photoexcitation, the ferroelectric and spiral-spin orders remain interlocked while relaxing through spin-lattice relaxation in the non-equilibrium state. When the additional optical pulse illuminating sample is intense enough to induced local phase transition thermally, the system creates a metastable state of bc-spiral-spin order (with electric polarization P//c) via supercooling across the first-order phase transition between the ab- and bc-spiral. The supercooled state of bc-spiral spin is formed in thermodynamical ground state of the ab-spiral (P//a), displaying a prolonged lifetime, in particular under its favorable magnetic field along the a-axis. The observed photo-switching between the two distinct multiferroic states sheds light on novel photoinduced phenomena in spiral-spin multiferroics.

Keywords: metastable, multiferroic, SHG, time-resolved, spiral spin