Spin freezing in the disordered pyrochlore magnet NaCaCo2 F7: NMR studies and Monte Carlo simulations

R. Sarkar, J. W. Krizan, F. Brückner, E. C. Andrade, S. Rachel, M. Vojta, R. J. Cava, H. H. Klauss

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Abstract

We present results of Na23 and F19 nuclear magnetic resonance (NMR) measurements on NaCaCo2F7, a frustrated pyrochlore magnet with a Curie-Weiss temperature ΘCW≈-140 K and intrinsic bond disorder. Below 3.6 K both the Na23 and F19 spectra broaden substantially in comparison to higher temperatures accompanied by a considerable reduction (80%) of the NMR signal intensity: This proves a broad quasistatic field distribution. The F19 spin-lattice relaxation rate 19(1/T1) exhibits a peak at 2.9 K already starting to develop below 10 K. We attribute the spin freezing to the presence of bond disorder. This is corroborated by large-scale Monte Carlo simulations of a classical bond-disordered XY model on the pyrochlore lattice. The low freezing temperature, together with the very short magnetic correlation length not captured by the simulations, suggests that quantum effects play a decisive role in NaCaCo2F7.

Original languageEnglish (US)
Article number235117
JournalPhysical Review B
Volume96
Issue number23
DOIs
StatePublished - Dec 12 2017

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

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    Sarkar, R., Krizan, J. W., Brückner, F., Andrade, E. C., Rachel, S., Vojta, M., Cava, R. J., & Klauss, H. H. (2017). Spin freezing in the disordered pyrochlore magnet NaCaCo2 F7: NMR studies and Monte Carlo simulations. Physical Review B, 96(23), [235117]. https://doi.org/10.1103/PhysRevB.96.235117