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arXiv · 1909.13734

Nature of the field-induced magnetic incommensurability in multiferroic Ni$_3$TeO$_6$

J. Lass·Ch. Røhl Andersen·H. K. Leerberg·S. Birkemose·S. Toth·U. Stuhr·M. Bartkowiak·Ch. Niedermayer·Zhilun Lu·R. Toft-Petersen·M. Retuerto·J. Okkels Birk·K. Lefmann
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Abstract

Using single crystal neutron scattering we show that the magnetic structure Ni$_3$TeO$_6$ at fields above 8.6 T along the $c$ axis changes from a commensurate collinear antiferromagnetic structure with spins along c and ordering vector $Q_C$= (0 0 1.5), to a conical spiral with propagation vector $Q_{IC}$= (0 0 1.5$\pm\delta$),$\delta\sim$0.18, having a significant spin component in the ($a$,$b$) plane. We determine the phase diagram of this material in magnetic fields up to 10.5 T along $c$ and show the phase transition between the low field and conical spiral phases is of first order by observing a discontinuous jump of the ordering vector. $Q_{IC}$ is found to drift both as function of magnetic field and temperature. Preliminary inelastic neutron scattering reveals that the spin wave gap in zero field has minima exactly at $Q_{IC}$ and a gap of about 1.1 meV consisting with a cross-over around 8.6 T. Our findings excludes the possibility of the inverse Dzyaloshinskii-Moriya interaction as a cause for the giant magneto-electric coupling earlier observed in this material and advocates for the symmetric exchangestriction as the origin of this effect.

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J. Lass, Ch. Røhl Andersen, H. K. Leerberg, S. Birkemose, S. Toth, U. Stuhr, M. Bartkowiak, Ch. Niedermayer, Zhilun Lu, R. Toft-Petersen, M. Retuerto, J. Okkels Birk, K. Lefmann. 2019-09-30. Nature of the field-induced magnetic incommensurability in multiferroic Ni$_3$TeO$_6$. https://doi.org/10.1103/physrevb.101.054415

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