Regensburg 2019 – scientific programme

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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur

KFM 16: Multiferroics and Magnetoelectric coupling II (joint session MA/KFM)

KFM 16.5: Talk

Friday, April 5, 2019, 10:30–10:45, H39

Complex magnon spectrum of the simple collinear antiferromagnet Co₂Mo₃O₈ — •Stephan Reschke¹, Dániel Farkas², Sandor Bordács², Vladimir Tsurkan¹, and István Kézsmárki¹ — ¹University of Augsburg, Augsburg, Germany — ²Budapest University of Technology and Economics, Budapest, Hungary

Co₂Mo₃O₈ belongs to a family of hexagonal lattice type-I multiferroics, showing peculiar magnetoelectric effects. In this compound the magnetic Co²⁺ ions are in either tetrahedral or octahedral oxygen coordination and form honeycomb layers in the ab plane. Based on neutron powder diffraction, Co₂Mo₃O₈ is a 4 sub-lattice collinear easy-axis antiferromagnet below T_N = 42 K. By THz time-domain spectroscopy measurements the magnon excitation spectra of differently oriented single crystals were investigated in magnetic fields up to 7 T. Interestingly, we observed magnon spectra far more complicated than expected for the proposed simple antiferromagnetic structure, with more than 20 magnon modes. Most of these modes show a splitting for magnetic fields applied along the c axis, which supports the predominantly easy-axis character of the antiferromagnetic state. Furthermore, we also observed directional dichroism for some of the modes, a consequence of the dynamic magnetoelectric effects.