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Spin waves in the ferromagnetic ground state of the kagome staircase system Co3V2O8

M. Ramazanoglu, C. P. Adams, J. P. Clancy, A. J. Berlinsky, Z. Yamani, R. Szymczak, H. Szymczak, J. Fink-Finowicki, and B. D. Gaulin
Phys. Rev. B 79, 024417 – Published 15 January 2009
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  • INTRODUCTION
  • EXPERIMENTAL DETAILS
  • RESULTS
  • CONCLUSION
  • ACKNOWLEDGEMENTS
    • References

    Abstract

    Inelastic neutron-scattering measurements were performed on single-crystal Co3V2O8 wherein magnetic cobalt ions reside on distinct spine and cross-tie sites within kagome staircase planes. This system displays a rich magnetic phase diagram which culminates in a ferromagnetic ground state below TC∼6 K. We have studied the low-lying magnetic excitations in this phase within the kagome plane. Despite the complexity of the system at higher temperatures, linear spin-wave theory describes most of the quantitative detail of the inelastic neutron measurements. Our results show two spin-wave branches, the higher energy of which displays finite spin-wave lifetimes well below TC, and that, surprisingly, the magnetic exchange coupling between Co moments on the spine sites is negligible.

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    • Received 25 October 2008

    DOI:https://doi.org/10.1103/PhysRevB.79.024417

    ©2009 American Physical Society

    Authors & Affiliations

    M. Ramazanoglu1, C. P. Adams1,2, J. P. Clancy1, A. J. Berlinsky1,3, Z. Yamani4, R. Szymczak5, H. Szymczak5, J. Fink-Finowicki5, and B. D. Gaulin1,3

    • 1Department of Physics and Astronomy, McMaster University, Hamilton, Ontario, Canada L8S 4M1
    • 2Department of Physics, St. Francis Xavier University, Antigonish, Nova Scotia, Canada B2G 2W5
    • 3Canadian Institute for Advanced Research, 180 Dundas Street West, Toronto, Ontario, Canada M5G 1Z8
    • 4Canadian Neutron Beam Centre, National Research Council, Chalk River Laboratories, Chalk River, Ontario, Canada K0J 1P0
    • 5Institute of Physics, Polish Academy of Sciences, 02-668 Warsaw, Poland

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    Issue

    Vol. 79, Iss. 2 — 1 January 2009

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    Images

    • Figure 1
      Figure 1
      (Color online) (a) A schematic diagram of the kagome staircase layer drawn in three dimensions (shown only for Co ions). The Co ions are represented by blue (dark gray) and red spheres (light gray) for spine (M1) and cross-tie (M2) sites, respectively. (b) The same structure shown in (a) as reduced to two dimensions in the a−c plane. (c) The basis used in the linear spin-wave theory calculation.Reuse & Permissions
    • Figure 2
      Figure 2
      Representative constant-Q INS spectra with (a) Q=(1.8,0,0) and (b) (0, 0, 1.8) at T=3 K (FM phase). The broken line shows the resolution-corrected fits to the data, as described in text. The solid horizontal bars indicate the instrumental energy resolution. The inset shows heating and cooling scans of the (mainly) magnetic elastic (002) Bragg scattering, which is characteristic of the FM ground state in CVO.Reuse & Permissions
    • Figure 3
      Figure 3
      (Color) [(a) and (c)] Color contour maps of INS at T=3 K and [(b) and (d)] corresponding linear spin-wave theory as described in the text. The broken lines show the dispersion relations resulting from this spin-wave theory analysis.Reuse & Permissions
    • Figure 4
      Figure 4
      (Color online) (a) INS scans at Q=(3.4,0,0) for T=3 and 20 K. The inset shows the temperature dependence of the scattering at the inelastic peak position. The lines in the inset are guides to the eyes. (b) The same data in panel (a) and DHO fits with log intensity axis. (c) Scans in the PM phase for Q=(1.8,0,0) and (0, 0, 1.8). The inset (same legend as main figure) shows the temperature dependence of the inelastic scattering at the spin-wave peak (for T=3 K, see Fig. 2) at ΔE=1.86 meV for the different Q directions. The vertical dotted lines in the inset indicate TC and TN.Reuse & Permissions
    • Figure 5
      Figure 5
      (Color online) Comparison between the measured spin-wave energies, as determined by fitting neutron groups to DHO line shapes, and the results of the spin-wave theory calculation, as described in text. The spin-wave theory results have been fitted to the experiment, both of which are shown along the [h00] and [00l] scattering directions in panels (a) and (b), respectively.Reuse & Permissions
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