Berlin 2008 – wissenschaftliches Programm

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SYNF: Symposium Ferroic materials and novel functionalities

SYNF 2: Ferroic materials and novel functionalities II

SYNF 2.3: Hauptvortrag

Dienstag, 26. Februar 2008, 15:30–16:00, A 151

Gigantic magnetoelectic responses in hellimagnets — •Y. Tokura — Department of Applied Physics, University of Tokyo, Tokyo 113-8656, Japan

Multiferroics, the materials in which both (anti)ferromagnetism and ferroelectricity can coexist, are the prospective candidate which can potentially host the gigantic magnetoelectric (ME) effect. A useful hint to designing of the strong magnetoelectric coupling has been gained by the recent discovery of the ferroelectricity in the transverse-spiral magnets, such as perovskite manganites. The multiferroics based on the spin-current (or inverse Dzyaloshinskiy-Moriya interaction) mechanism has recently been realized also in the conical spin state of chromite spinels where the transverse spiral component coexists with the uniform magnetization component along the cone axis. In those compounds, the clamping between the magnetic and ferroelectric domains can show up, perhaps enabling the magnetic (electric) control of the ferroelectric (ferromagnetic) domains. Multiferroics with the strong ME correlation may also provide a unique arena to test new optical effects. This includes the so-called magnetization-induced second harmonic generation (MSHG) and the nonreciprocal dichroism dependent on the light propagation direction (but not on the light polarization), termed the optical magnetoelectric (OME) effect as well as the electrically driven spin excitations like electromagnons. We present the late advances in our study of exploring such hellimagnets (screw, cycloidal, and conical magnets) as showing strong ME coupling and novel optical responses.