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Dynamics of Magnetic Defects in Heavy Fermion LiV2O4 from Stretched Exponential Li7 NMR Relaxation

D. C. Johnston, S.-H. Baek, X. Zong, F. Borsa, J. Schmalian, and S. Kondo
Phys. Rev. Lett. 95, 176408 – Published 21 October 2005
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Abstract

Li7 NMR measurements on LiV2O4 from 0.5 to 4.2 K are reported. A small concentration of magnetic defects within the structure drastically changes the Li7 nuclear magnetization relaxation versus time from a pure exponential as in pure LiV2O4 to a stretched exponential, indicating glassy behavior of the magnetic defects. The stretched exponential function is described as arising from a distribution of Li7 nuclear spin-lattice relaxation rates and we present a model for the distribution in terms of the dynamics of the magnetic defects. Our results explain the origin of recent puzzling Li7 NMR literature data on LiV2O4 and our model is likely applicable to other glassy systems.

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  • Received 21 March 2005

DOI:https://doi.org/10.1103/PhysRevLett.95.176408

©2005 American Physical Society

Authors & Affiliations

D. C. Johnston, S.-H. Baek*, X. Zong, F. Borsa, J. Schmalian, and S. Kondo†

  • Ames Laboratory and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA

  • *Present address: National High Magnetic Field Laboratory, Tallahassee, FL 32310.
  • †Present address: Materials Laboratories, Sony Corporation, Haneda TEC., 5-21-15 Higashikojiya, Ota-ku, Tokyo 144-0033, Japan.

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Vol. 95, Iss. 17 — 21 October 2005

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  • Figure 1
    Figure 1
    (a) Li7 NMR line shape at 0.5 and 4.2 K and full width at half maximum peak intensity versus temperature (FWHM, inset) for two samples of LiV2O4. (b) Hole-burning spectra at 4.2 K for sample #3-3-a2.Reuse & Permissions
  • Figure 2
    Figure 2
    Recovery of the Li7 nuclear magnetization M vs time t for LiV2O4 samples #12-1 (a) and #3-3-a2 (b). The solid curves in (a) and (b) are fits to the data at each T by an exponential and a stretched exponential, respectively.Reuse & Permissions
  • Figure 3
    Figure 3
    Li7 nuclear spin-lattice relaxation rates in LiV2O4 vs temperature T. The lowest data set of 1/T1 vs T is for high purity sample #12-1; the fitted straight line is the Korringa law for a Fermi liquid. The 1/T1* vs T data sets are for our sample #3-3-a2 (filled squares) and from Kaps et al. [Ref. 10 ] (open squares). The vertical arrow at about 0.7 K indicates the approximate T of the maxima in 1/T1*. The inset shows the exponent β in the stretched exponential in Eq. (1) vs T.Reuse & Permissions
  • Figure 4
    Figure 4
    Probability density P(s) for several stretched exponential exponents β. The inset shows the s values versus β at which P(s) is maximum.Reuse & Permissions
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