Location via proxy:   [ UP ]  
[Report a bug]   [Manage cookies]                
  • Editors' Suggestion

Frustration model and spin excitations in the helimagnet FeP

A. S. Sukhanov, Y. V. Tymoshenko, A. A. Kulbakov, A. S. Cameron, V. Kocsis, H. C. Walker, A. Ivanov, J. T. Park, V. Pomjakushin, S. E. Nikitin, I. V. Morozov, I. O. Chernyavskii, S. Aswartham, A. U. B. Wolter, A. Yaresko, B. Büchner, and D. S. Inosov
Phys. Rev. B 105, 134424 – Published 20 April 2022
PDFHTMLExport Citation
Abstract
Authors
Article Text
  • INTRODUCTION
  • SAMPLE CHARACTERIZATION AND EXPERIMENTAL…
  • TOF SPECTROSCOPY
  • MODEL OF FRUSTRATED CHAINS
  • DISCUSSION
  • CONCLUSION
  • ACKNOWLEDGMENTS
    • Supplemental Material
    References

    Abstract

    The metallic compound FeP belongs to the class of materials that feature a complex noncollinear spin order driven by magnetic frustration. While its double-helix magnetic structure with a period λs≈5c, where c is the lattice constant, was previously well determined, the relevant spin-spin interactions that lead to that ground state remain unknown. By performing extensive inelastic neutron scattering measurements, we obtained the spin-excitation spectra in a large part of the momentum-energy space. The spectra show that the magnons are gapped with a gap energy of ∼5meV. Despite the 3D crystal structure, the magnon modes display strongly anisotropic dispersions, revealing a quasi-one-dimensional character of the magnetic interactions in FeP. The physics of the material, however, is not determined by the dominating exchange, which is ferromagnetic. Instead, the weaker two-dimensional antiferromagnetic interactions between the rigid ferromagnetic spin chains drive the magnetic frustration. Using linear spin-wave theory, we were able to construct an effective Heisenberg Hamiltonian with an anisotropy term capable of reproducing the observed spectra. This enabled us to quantify the exchange interactions in FeP and determine the mechanism of its magnetic frustration.

    • Figure
    • Figure
    • Figure
    • Figure
    • Figure
    • Figure
    • Figure
    • Received 25 January 2022
    • Accepted 5 April 2022

    DOI:https://doi.org/10.1103/PhysRevB.105.134424

    ©2022 American Physical Society

    Physics Subject Headings (PhySH)

    1. Research Areas
    Frustrated magnetismSpin dynamics
    1. Physical Systems
    Helimagnets
    1. Techniques
    Inelastic neutron scattering
    Condensed Matter, Materials & Applied Physics

    Authors & Affiliations

    A. S. Sukhanov1, Y. V. Tymoshenko1,*, A. A. Kulbakov1, A. S. Cameron1, V. Kocsis2, H. C. Walker3, A. Ivanov4, J. T. Park5, V. Pomjakushin6, S. E. Nikitin7, I. V. Morozov2, I. O. Chernyavskii2, S. Aswartham2, A. U. B. Wolter2, A. Yaresko8, B. Büchner1,2,9, and D. S. Inosov1,9,†

    • 1Institut für Festkörper- und Materialphysik, Technische Universität Dresden, D-01069 Dresden, Germany
    • 2Institut für Festkörperforschung, Leibniz IFW-Dresden, D-01069 Dresden, Germany
    • 3ISIS Facility, STFC, Rutherford Appleton Laboratory, Didcot, Oxfordshire OX11-0QX, United Kingdom
    • 4Institut Laue-Langevin, 71 avenue des Martyrs, CS 20156, 38042 Grenoble Cedex 9, France
    • 5Heinz Maier-Leibnitz Zentrum (MLZ), TU München, D-85747 Garching, Germany
    • 6Laboratory for Neutron Scattering and Imaging (LNS), Paul Scherrer Institute (PSI), CH-5232 Villigen, Switzerland
    • 7Paul Scherrer Institute (PSI), CH-5232 Villigen, Switzerland
    • 8Max-Planck-Institut für Festkörperforschung, Heisenbergstrasse 1, D-70569 Stuttgart, Germany
    • 9Würzburg-Dresden Cluster of Excellence on Complexity and Topology in Quantum Matter—ct.qmat, Technische Universität Dresden, 01069 Dresden, Germany

    • *Present address: Institute for Quantum Materials and Technologies, Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany.
    • †Corresponding author: dmytro.inosov@tu-dresden.de

    Article Text (Subscription Required)

    Click to Expand

    Supplemental Material (Subscription Required)

    Click to Expand

    References (Subscription Required)

    Click to Expand
    Issue

    Vol. 105, Iss. 13 — 1 April 2022

    Reuse & Permissions
    Access Options
    Author publication services for translation and copyediting assistance advertisement

    Authorization Required

    Log In
    Other Options
    ×

    Images

    • Figure 1
      Figure 1

      (a) The double-helix magnetic structure of FeP reported in [20] (only Fe atoms are shown). The chosen enumeration of the Fe sites in the unit cell is shown beside the spins. (b) The same as in (a) but viewed from the c axis. The spin angles are defined via the parameters k and α (see text) as shown. (c) The Fe sublattice with the bonds between the nearest-neighbor sites shown as solid lines. A trapezoidal structural motif formed by four Fe sites in the unit cell is highlighted in magenta. (d) A schematic of the magnetic interactions induced within the trapezoid illustrating the magnetic frustration. (e) The classical phase diagram of the Ja1−Jc1−Jc2 model (the frustrated trapezoid, see text), HM and CM stand for the helimagnet and collinear magnet, respectively. FeP is placed on the phase diagram as suggested by [35]. (f) The absolute value of the lowest-energy propagation vector k as a function of the exchange constants within the discussed model. (g) The lowest-energy canting angle α as a function of the exchange constants. The green-solid lines show k and α of FeP.

      Reuse & Permissions
    • Figure 2
      Figure 2

      (a) Thermal expansion measurements of single-crystal FeP along the principal crystallographic directions in zero and applied magnetic fields. The blue line shows the average of three zero-field curves, which represents volume expansion. (b) Magnetization as a function of temperature for a magnetic field applied along the principal crystallographic directions. (c) Magnetization curves at T=2K. (d) Specific heat measurements in zero field, with the transition region enlarged in the inset.

      Reuse & Permissions
    • Figure 3
      Figure 3

      Time-of-flight neutron spectroscopy data at T=7.5K. [(a)–(c)] The momentum-energy slice through the data for the H (a), K (b), and L (c) reciprocal-space directions across the magnetic satellites of the (110) point. The data obtained with four different incident neutron energies Ei were combined in a single plot as labeled. The data were integrated over a finite range in the perpendicular momenta (see Supplemental Material [37] for the integration range that corresponds to each slice). The white arrows show phonon modes. (d) The elastic scattering in the (H1L) plane. The dotted lines show the direction of the momentum cuts for (a) and (c). (e) The INS intensity as a function of energy transfer for the momenta that correspond to the magnetic satellites of (101) and (110).

      Reuse & Permissions
    • Figure 4
      Figure 4

      The simulated magnon spectra for FeP within the model of frustrated trapezoid along the L [(a),(d)] and H [(b),(e)] reciprocal-space directions for the parameter α=4∘ [(a),(b)] and α=30∘ [(d),(e)]. (c) The ratios of the exchange interactions Jc1/Ja1 and Jc2/Ja1 as a function of the angle α highlighting the case of α=4∘ and α=30∘.

      Reuse & Permissions
    • Figure 5
      Figure 5

      (a) The exchange interaction scheme of the model of frustrated AFM chains. The crystal-structure sublattice of Fe atoms is shown in the ac plane. The magenta trapezoid highlights the structural motif formed by the four Fe atoms in the unit cell of FeP. (b) The schematics of the frustrated zigzag spin chains, which represent the same model as in (a) when the difference between the Jc1 and Jc2 bonds is neglected.

      Reuse & Permissions
    • Figure 6
      Figure 6

      TAS constant-energy data (symbols) for the measurements along the K direction in the (0KL) plane shown for different energies and different values of L. The solid lines are fits by a sum of two Gaussian functions. The data were offset for clarity.

      Reuse & Permissions
    • Figure 7
      Figure 7

      [(a)–(d)] The TAS measurements of FeP for the momenta along the reciprocal directions (11L) at T=2K (a), (10L) at T=3.5K (b), (00L) at T=2K (c), and (H00.8) at T=3.5K (d). The horizontal red dotted lines separate the data collected with different kf. The sharp streak of intensity in the ∼5–20meV range in (a) is a measurement artefact due to neutrons that scattered at the (111) Bragg peak of the sample and further scattered incoherently off the analyser. The spectrally-sharp weakly dispersing mode at ∼25meV is an optic phonon [44]. [(e)–(h)] The linear spin-wave theory simulations of the magnon spectra (colormap) in FeP within the model of Eq. (4). To account for the energy-momentum resolution in the TAS measurements, all the simulated spectra were broadened by 3 meV in energy and integrated in the perpendicular momenta over ±0.06 r.l.u. in H and ±0.04 r.l.u. in K in [(e)–(g)], and ±0.07 r.l.u. in L and ±0.04 r.l.u. in K in (h). The solid lines show the simulated dispersion relations (only the modes that show a significant INS intensity are drawn, for the full set of dispersions see Supplemental Material [37]). Vertical dashed white lines mark the orthorhombic BZ boundary.

      Reuse & Permissions
    ×

    Sign up to receive regular email alerts from Physical Review B

    Log In

    Cancel
    ×

    Search

    Article Lookup

    Paste a citation or DOI
    Enter a citation
    ×