Berlin 2005 – wissenschaftliches Programm
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MA: Magnetismus
MA 20: Poster:Schichten(1-29),Spintrsp(30-45),Ex-Bias(46-63),Spindyn(64-75),Mikromat.(76-80),Cluster(81-94),Abbv.(95-99),Obflm(100-02),SpElek.(103-09),E-Theo(110-14),Mikromag.(115-16),Spin+PÜ(117-26),Mag.Mat.(127-51),Meth.(152-55),Mol.Mag(156-59),Kondo(160-65
MA 20.56: Poster
Montag, 7. März 2005, 14:00–18:00, Poster TU C
“Gigantic” Magnetoelectric Effect in Multiferroic Manganites — •M. Fiebig1, Th. Lottermoser1 und T. Lonkai1,2,3 — 1Max-Born-Institut, Max-Born-Straße 2a, 12489 Berlin — 2Institut für Angewandte Physik, Universität Tübingen, Auf der Morgenstelle 10, 72076 Tübingen — 3Hahn-Meitner-Institut, Glienicker Straße 100, 14109 Berlin
The crosslink between magnetic and electric properties expressed by the magnetoelectric (ME) effect opens new degrees of freedom for device construction. Recently, an enormous interest in ME phenomena is observed because composite materials and multiferroics, i.e. materials with multiple magnetic, electric and/or elastic ordering, exhibit structural and gigantic ME effects which exceed previous effects by many orders of magnitude and control phase transitions. We will discuss three types of “gigantic” ME coupling that were observed in ferroelectric (FEL) antiferromagnetic (AFM) RMnO3 (R = Sc, Y, In, Ho-Lu). (i) An external magnetic or electric field induces ferromagnetic R3+ ordering which is reversibly switched on or off. The process is monitored by magneto-optical techniques (second harmonic generation, Faraday rotation). Its microscopic origin is disclosed by neutron and x-ray powder diffraction. (ii) An interaction of FEL and AFM domain walls which clamps the AFM to the FEL domain structure. It roots in piezomagnetic interaction between magnetization of the AFM walls and strain in the FEL walls which lowers the free energy. (iii) A massive formation of spin-rotation domains which supplement spin-reversal domains in the course of a reorientation of Mn3+ spins. This leads to a local ME effect which is only allowed because of the low symmetry of the domain walls.