Dresden 2006 – scientific programme

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SYMM: Multi-ferroic materials

SYMM 2: Multiferroic Materials - Experiment

SYMM 2.3: Invited Talk

Tuesday, March 28, 2006, 17:15–17:45, HSZ 04

Magnetoelectric Effect and Toroidal Ordering in Multiferroic Manganites — •M. Fiebig¹, Th. Lottermoser¹, and Th. Lonkai² — ¹Max-Born-Institut, Max-Born-Strasse 2A, 12489 Berlin, Germany — ²Institut für Angewandte Physik, Universität Tübingen, 72076 Tübingen, Germany; and Hahn-Meitner-Institut, Glienicker Strasse 100, 14109 Berlin, Germany

Recently, an enormous interest in multiferroic compounds which unite two or more different forms of primary ferroic ordering in one phase is observed. Aside from technological aspects the interplay of different forms of (anti-) ferroic ordering is a rich source for exploring the fundamental science of phase control. I will discuss the coexistence of magnetic and electrical ordering in the hexagonal rare-earth manganites RMnO₃ (R=Ho,Yb). With ferroelectricity and magnetic Mn³⁺ and R³⁺ ordering the compounds possess 4 ordered sublattices. I will show how microscopic magnetoelectric correlations between sublattices in combination with multiple frustration lead to giant manifestations of macroscopic magnetoelectric behavior. This leads to magnetic phase control by external electric or magnetic fields or temperature. Furthermore, I will argue that in addition to ferromagnetism, ferroelectricity, and ferroelasticity as the three widely known forms of primary ferroic ordering, ferrotoroidicity formation of a spontaneous magnetic vortex must be included as the fourth variety. Toroidic domains can exist and have already been observed in multiferroic YMnO₃, but were not recognized as such. However, after introducing toroidic domains as physically independent states the former observation becomes physically sound.