Berlin 2005 – wissenschaftliches Programm
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MA: Magnetismus
MA 5: Spinstrukturen und magnetische Phasenüberg
änge
MA 5.9: Vortrag
Freitag, 4. März 2005, 12:30–12:45, TU EMH225
Giant Magnetoelectric Response in Multiferroic Manganites due to Rare Earth Ordering — •Thomas Lonkai1,2, Uwe Amann1,3, Manfred Fiebig4, Dana Tomuta5, Dietmar Hohlwein1,2, and Jörg Ihringer1,2 — 1Institute for Applied Physics, University of Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany — 2Hahn-Meitner-Institut, Berlin, Glienicker Str. 100, 14109 Berlin, Germany — 3Institut Laue-Langevin, 6 Rue Jules Horowitz, BP 156 - 38042 Grenoble Cedex 9, France — 4Max-Born-Institut, Max-Born-Straße 2A, 12489 Berlin, Germany — 5Kamerlingh Onnes Laboratory, Leiden University, P.O. Box 9504, 2300 RA Leiden, The Netherlands
We analysed the zero field magnetoelectric phase transitions in hexagonal ErMnO3 and HoMnO3 by second harmonic generation, measurements of the specific heat, and neutron powder and single crystal diffraction. The magnetic phase transitions from P63′cm′ to P63cm (HoMnO3) and P63′c′m to P63c′m′ (ErMnO3) were determined by second harmonic generation. Specific heat data shows the magnetoelectric contribution to the free energy. Refinements of the neutron diffraction data, based on the results of the known symmetries, determines the displacements of the atomic positions and the magnetic ordering process.
Our experiments shows the importance of the rare earth ordering process in the magnetoelectric phase transitions in hexagonal manganites. Due to the large magnetic moment of Er3+ and Ho3+ the magnetoelectric contribution to the free energy is large enough to trigger an electric phase transition of the O-Mn-O-axis of the MnO5 coordination polyhedra.