Berlin 2008 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 20: Multiferroics

MA 20.9: Vortrag

Mittwoch, 27. Februar 2008, 16:15–16:30, EB 202

Electromagnons in rare earth multiferroics DyMnO₃ and TbMnO₃ — •Alexey Shuvaev¹, Alexander Mukhin², Anatoli Balbashov³, Alois Loidl⁴, and Andrei Pimenov¹ — ¹Experimentelle Physik IV, Universität Würzburg, 94074 Würzburg, Germany — ²General Physics Institute of the Russian Academy of Sciences, 119991 Moscow, Russia — ³Moscow Power Engineering Institute, 111250 Moscow, Russia — ⁴Experimentalphysik V, EKM, Universität Augsburg, 86135 Augsburg, Germany

Dielectric permittivity spectra of rare earth multiferroic manganites DyMnO₃ and TbMnO₃ have been investigated in the terahertz frequency range. Similar to other multiferroics well-defined magnetoelectric excitations (electromagnons) are observed in the incommensurate magnetic phases below T = 40 K. Electromagnons are excitations of the incommensurate magnetic structure and, contrary to magnons, can be excited solely by electric component of the electromagnetic wave. Application of external magnetic fields strongly modifies the permittivity spectra in both compositions leading to magnetoelectric effects down to zero frequencies. In TbMnO₃ and in moderate fields additional structure appears close to ν ∼ 10 cm⁻¹ and is suppressed again for magnetic fields above 5 T. Manifestations of different magnetic phase boundaries in the spectra of the dielectric permittivity are discussed.