Neutron Scattering and µSR Studies of Spin Fluctuations in Frustrated Itinerant Magnets

  • B. D. Rainford
  • S. J. Dakin
  • J. R. Stewart
  • R. Cywinski
Chapter
Part of the NATO Science Series book series (ASHT, volume 55)

Abstract

Extensive measurements have been made of the spin dynamics of YMn2and its alloys, and of β-Mn and β-Mn-Al alloys, using a combination of inelastic neutron scattering and muon spin relaxation. The dynamical response measured by time-of flight neutron spectroscopy in YMn2alloys is strongly peaked at the characteristic wavevectors of the antiferromagnetic spin fluctuations. It appears that the wavevectors found in recent single crystal studies of YMn2are similar to those found in Monte Carlo simulations of localised moments in the antiferromagnetic pyrochlore lattice. In YMn2alloys the neutron linewidths are strongly correlated with the unit cell volume: substitution of Mn by Al expands the cell and decreases the linewidth, while substitutions of Sc for Y and Fe for Mn contract the cell and increase the linewidth. µSR measurements on β-Mn-Al alloys show a crossover from the Lorentzian to stretched exponential damping above 9% Al, the concentration at which the spin glass temperature begins to rise rapidly. This suggests a regime dominated by spin fluctuations below 9% Al and a regime with stable Mn moments above this composition.

Keywords

Spin Glass Inelastic Neutron Spin Fluctuation Inelastic Neutron Scattering Magnetic Phase Diagram 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.
This is a preview of subscription content, log in to check access.

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. 1.
    Shiga, M. (1988) Magnetism and spin fluctuations of Laves phase manganese compoundsPhysica B 149, 293–305, and references therein.Google Scholar
  2. 2.
    Nakamura, H., Yoshimoto, K., Shiga, M., Nishi, M. and Kakurai, K. (1997) Strong antiferromagnetic spin fluctuations and the quantum spin-liquid state in geometrically frustrated 3-Mn, and the transition to a spin-glass state caused by a non-magnetic impurity, J.Phys.: Condens. Matter 9, 4701–4728.ADSCrossRefGoogle Scholar
  3. Déportes, J., Ouladiaff, B. and Ziebeck, K.R.A. (1987) Spin fluctuations in the paramagnetic state of YMn2, J. Magn. Magn. Mater. 70, 14–16ADSCrossRefGoogle Scholar
  4. ibid. (1987) Thermal dependence of the longitudinal spin fluctuations in YMn2, J. Physique 48, 1029–1034.CrossRefGoogle Scholar
  5. 4.
    Freltoft, T., Böni, P., Shirane, G. and Motoya, K. (1988) Neutron scattering study of the itinerant electron magnet YMn2 Phys. Rev. B 37, 3454–3460;ADSCrossRefGoogle Scholar
  6. Motoya, K., Freltoft, T., Böni, P. and Shirane, G. (1988) Neutron scattering study of spin fluctuations in Y(Mn1-xA1x)2, Phys. Rev. B38, 4796–4802.ADSCrossRefGoogle Scholar
  7. 5.
    Rainford, B.D., Dakin, S.J. and Cywinski, R. (1992) Spin fluctuations in YMn2 and related alloys, J.Magn. Magn. Mater.104–107, 1257–1263.ADSCrossRefGoogle Scholar
  8. 6.
    Dakin, S.J., (1993), Ph.D. thesis (unpublished), Southampton University.Google Scholar
  9. 7.
    Ballou, R., Leliévre-Berna, E. and Fåk, B. (1996) Spin fluctuations in (Y0.97Sc0.03)Mn2: a geometrically frustrated, nearly antiferromagnetic, itinerant electron system.Phys. Rev. Lett. 76, 2125–2128.ADSCrossRefGoogle Scholar
  10. 8.
    Reimers, J.N. (1992) Absence of long range order in a three dimensional geometrically frustrated antiferromagnet, Phys. Rev. B 45, 7287–7294.ADSCrossRefGoogle Scholar
  11. 9.
    Zinkin, M.P. and Harris, M.J. (1995) Local mean field calculation of the frustrated pyrochlore spin structure, J.Magn. Magn. Mater. 140–144, 1803–1804.ADSCrossRefGoogle Scholar
  12. 10.
    Chalker, J.T., private communication.Google Scholar
  13. 11.
    Pinettes, C. and Lacroix, C. (1994) A model for heavy fermion behaviour of YMn2 —influence of frustration on the spin fluctuation spectrum, J. Phys.: Conden. Matter 6, 10093–10104.ADSCrossRefGoogle Scholar
  14. 12.
    Moriya, T. (1985)Spin Fluctuations in Itinerant Electron Magnetism, Springer-Verlag, Berlin.Google Scholar
  15. 13.
    Rainford, B.D., Cywinski, R., and Dakin, S.J. (1995) Neutron and OR studies of spin fluctuations in YMn2 and related alloys, J.Magn. Magn. Mater. 140–144, 805–806.ADSCrossRefGoogle Scholar
  16. 14.
    Cywinski, R., Kilcoyne, S.H. and Scott, C.A. (1991) Magnetic order and moment stability in YMn2 J. Phys.: Condens. Matter3, 6473–6488.ADSCrossRefGoogle Scholar
  17. 15.
    Cywinski, R., Kilcoyne, S.H., Cox, S.F.J, Scott, C.A. and Schaerpf, O. (1990) A µSR and neutron polarisation analysis study of Mn moment delocalisation in Fe substituted YMn2, Hyperfine Inter. 64427–434.ADSCrossRefGoogle Scholar
  18. 16.
    Cywinski, R. and Rainford, B.D. (1994) Spin dynamics in the spin glass phase of Y(Mn1-xAlx)2, Hyperfine Interactions 85, 215–220.ADSCrossRefGoogle Scholar
  19. 17.
    Stewart, J.R., Hillier, A.D., Kilcoyne, S.H., Manuel, P., Telling, M.T.F. and Cywinski, R. (1998) Mo-ment Localisation in βMnAl, J.Magn. Magn. Mater.(Proceedings of ICM’97) to be published.Google Scholar

Copyright information

© Springer Science+Business Media Dordrecht 1998

Authors and Affiliations

  • B. D. Rainford
    • 1
  • S. J. Dakin
    • 1
  • J. R. Stewart
    • 2
  • R. Cywinski
    • 2
  1. 1.Department of Physics and AstronomyUniversity of SouthamptonEngland
  2. 2.Department of Physics and AstronomyUniversity of St. AndrewsSt. AndrewsScotland

Personalised recommendations