Dresden 2006 – wissenschaftliches Programm

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MA: Magnetismus

MA 5: Spin-Structures and Magnetic Phase Transitions I

MA 5.1: Vortrag

Montag, 27. März 2006, 10:15–10:30, HSZ 403

Field induced incommensurate to commensurate magnetic transition in multiferroic TbMnO₃ — •Nadir Aliouane, Dimitri Argyriou, and Sven Landsgesell — Hahn-Meitner-Institut, Glienicker Str. 100, Berlin D-14109, Germany

TbMnO₃ is an improper ferroelectric that exhibits a flop in its electric polarization (P) with applied magnetic field (H) from P||c to P||a. It is argued that ferroelectricity here arises from a spiral spin phase that breaks inversion symmetry. We have used in-field neutron single crystal diffraction to monitor changes in the complex magnetic structure of this material as a function of magnetic field up to 14T and temperature. We show that the flop in the electric polarization that occurs at ∼9T and ∼5T for H along the a− and b−axis respectively coincides with a 1st order transition to a commensurate magnetic phase with propagation vector (0,1/4,0). On the basis of this commensurate magnetic phase we propose a model of structural distortions that correctly predicts the polarization direction of the high field phase.