Chiral order and multiferroic domain relaxation in NaFeGe$_2$O$_6$

S. Biesenkamp (1) , D. Gorkov (1, 2) , W. Schmidt (3) , K. Schmalzl (3) , Y. Sidis (4, 5) , P. Becker (6) , L. Bohatý (6) , M. Braden (1)

1 Physikalisches Institut [Köln]
2 MLZ - Heinz Maier-Leibnitz Zentrum
3 FZJ - Forschungszentrum Jülich GmbH | Centre de recherche de Jülich | Jülich Research Centre
4 LLB - UMR 12 - Laboratoire Léon Brillouin
5 NFMQ - LLB - Nouvelles frontières dans les matériaux quantiques
6 Institut für Geologie und Mineralogie [Köln]

The magnetic structure and the multiferroic relaxation dynamics of NaFeGe$_2$O$_6$ were studied by neutron scattering on single crystals partially utilizing polarization analysis. In addition to the previously reported transitions, the incommensurate spiral ordering of Fe$^{3+}$ moments in the $ac$ plane develops an additional component along the crystallographic b direction below T ≈ 5 K, which coincides with a lock-in of the incommensurate modulation. The quasistatic control of the spin-spiral handedness, respectively of the vector chirality, by external electric fields proves the invertibility of multiferroic domains down to the lowest temperature. Time-resolved measurements of the multiferroic domain inversion in NaFeGe$_2$O$_6$ reveal a simple temperature and electric-field dependence of the multiferroic relaxation that is well described by a combined Arrhenius-Merz relation, as it has been observed for TbMnO$_3$. The maximum speed of domain wall motion is comparable to the spin-wave velocity deduced from an analysis of the magnon dispersion.

Domaines: Physique [physics]; Electrons fortement corrélés [cond-mat.str-el]

S. Biesenkamp, D. Gorkov, W. Schmidt, K. Schmalzl, Y. Sidis, et al.. Chiral order and multiferroic domain relaxation in NaFeGe$_2$O$_6$. Physical Review B, 2021, 104 (17), pp.174405. ⟨10.1103/PhysRevB.104.174405⟩. ⟨hal-03795963⟩