Acoustic lattice instabilities at the magnetostructural transition in Fe1.057(7)Te

K. Guratinder, E. Chan, E. E. Rodriguez, J. A. Rodriguez-Rivera, U. Stuhr, A. Stunault, R. Travers, M. A. Green, N. Qureshi, C. Stock

Research output: Contribution to journalArticlepeer-review

Abstract / Description of output

Fe1.057(7)Te undergoes a first-order structural transition from a high temperature tetragonal phase to a low temperature monoclinic phase at TS∼70K, breaking the fourfold C4 high temperature lattice symmetry. At the same temperature, time reversal symmetry is broken with magnetic iron ions ordering in a commensurate (with the nuclear lattice) bicollinear arrangement. The low-energy magnetic dynamics proximate to this magnetostructural transition are, however, incommensurate and have been reported on previously [Stock et al., Phys. Rev. B 95, 144407 (2017)]. In this current work, we investigate the soft acoustic lattice dynamics near this combined magnetostructural transition. We apply spherically neutron polarimetry to study the static magnetism near this transition, characterized with x-ray powder diffraction, and find no evidence of static incommensurate magnetic correlations near the onset of monoclinic and bicollinear antiferromagnetic order. This fixes the position of our single crystal sample in the Fe1+xTe phase diagram in the magnetic bicollinear region and illustrates that our sample statically undergoes a transition from a paramagnetic phase to a low-temperature bicollinear phase. We then apply neutron spectroscopy to study the acoustic phonons, related to elastic deformations of the lattice. We find a temperature dependent soft acoustic branch for phonons propagating along [010] and polarized along [100]. The slope of this acoustic phonon branch is sensitive to the elastic constant C66 and the shear modulus. The temperature dependence of this branch displays a softening with a minimum near the magnetostructural transition of TS∼70K and a recovery within the magnetically ordered low temperature phase. Soft acoustic instabilities are present in the collinear phases of the chalcogenides Fe1+xTe, while nematic order found in Fe1+δSe is absent. We speculate, based on localized single-ion magnetism, that the relative energy scale of magnetic spin-orbital coupling on the Fe2+ transition metal ion is important for the presence of a nematicity in the chalcogenides.
Original languageEnglish
Article number214411
Pages (from-to)1-12
Number of pages12
JournalPhysical Review B
Issue number21
Early online date1 Dec 2023
Publication statusPublished - 13 Dec 2023

Keywords / Materials (for Non-textual outputs)

  • cond-mat.str-el
  • cond-mat.mtrl-sci


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