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MA: Fachverband Magnetismus
MA 59: Posters Magnetism III
MA 59.37: Poster
Freitag, 20. März 2020, 09:00–12:00, P2/EG
Dimerization in the commensurate antiferromagnetic phase of MnWO4 and NaFe(WO4)2 — •Sebastian Biesenkamp1, Yvan Sidis2, Navid Qureshi3, Dmitry Gorkov1, Karin Schmalzl4, Wolfgang Schmidt4, Petra Becker5, Ladislav Bohatý5, and Markus Braden1 — 1Institute of Physics II, University of Cologne — 2Laboratoire Léon Brillouin, CEA-CNRS, CEA/Saclay — 3ILL, Grenoble — 4JCNS at ILL, Grenoble — 5Sect. Crystallography, Institute of Geology and Mineralogy, University of Cologne
In multiferoic MnWO4, the relaxation time of the multiferroic domain inversion shows a peculiar temperature dependence. Upon cooling below the multiferroic transition the relaxation time first increases but becomes faster closer to the commensurate low-temperature phase [1]. We investigated anharmonicities in this material as well as in isostructural NaFe(WO4)2 and propose the enhanced anharmonicities close to the low-temperature magnetic up-up-down-down structure to be responsible for the faster relaxation rates in MnWO4. In both materials there is a similar competition between incommensurate cycloid and commensurate up-up-down-down order, and anharmonic squaring up appears as a precursor in the incommensurate structure [2]. The commensurate magnetic structure is associated with structural dimerization in both materials, that has been quantitatively determined for NaFe(WO4)2 by a four-circle neutron diffraction experiment. [1]: M. Baum, Phys. Rev. B 89, 144406 (2014) [2]: S. Holbein, Phys. Re. B 94, 104423 (2016)