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  Lass, J.; Røhl Andersen, Ch.; Leerberg, H. K.; Birkemose, S.; Toth, S.; Stuhr, U.; Bartkowiak, M.; Niedermayer, Ch.; Lu, Z.; Toft-Petersen, R.; Retuerto, M.; Okkels Birk, J.; Lefmann, K.: Field-induced magnetic incommensurability in multiferroic Ni₃TeO₆. Physical Review B 101 (2020), p. 054415/1-9

10.1103/PhysRevB.101.054415
Open Access Version (externer Anbieter)

Abstract:
Using single-crystal neutron diffraction we show that the magnetic structure Ni3TeO6 at fields above 8.6 T along the c axis and low temperature changes from a commensurate collinear antiferromagnetic structure with spins along c and ordering vector QC = (0 0 1.5) to a conical spiral with propagation vectorQIC = (0 0 1.5±δ), δ ∼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. QIC is found to drift both as a function of magnetic field and temperature. Preliminary inelastic neutron-scattering data reveal that the spinwave gap in zero field has minima exactly at QIC and a gap of about 1.1 meV consisting with a crossover around 8.6T. Further, a simple magnetic Hamiltonian accounting in broad terms for these is presented. Our findings confirm the exclusion of the inverse Dzyaloshinskii-Moriya interaction as a cause for the giant magnetoelectric due to symmetry arguments. In its place we advocate for the symmetric exchange striction as the origin of this effect.