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Pair correlations, short-range order, and dispersive excitations in the quasi-kagome quantum magnet volborthite

In English

Författare

  • G. J. Nilsen
  • F. C. Coomer
  • M. A. de Vries
  • J. R. Stewart
  • Pascale Deen
  • A. Harrison
  • H. M. Ronnow

Summary, in English

We present spatial and dynamic information on the s = 1/2 distorted kagome antiferromagnet volborthite, Cu3V2O7(OD)(2) center dot 2D(2)O, obtained by polarized and inelastic neutron scattering. The instantaneous structure factor, S(Q), is dominated by nearest-neighbor pair correlations, with short-range order at wave vectors Q(1) = 0.65(3) angstrom(-1) and Q(2) = 1.15(5) angstrom(-1) emerging below 5 K. The excitation spectrum, S(Q,omega), reveals two steep branches dispersing from Q(1) and Q(2), and a flat mode omega(f) = 5.0(2) meV. The results allow us to identify the crossover at T* similar to 1 K in V-51 NMR and specific-heat measurements as the buildup of correlations at Q(1). We compare our data to theoretical models proposed for volborthite, and also demonstrate that the excitation spectrum can be explained by spin-wave-like excitations with anisotropic exchange parameters, as suggested by recent local-density calculations.

Publiceringsår

2011

Språk

Engelska

Publikation/Tidskrift/Serie

Physical Review B (Condensed Matter and Materials Physics)

Volym

84

Issue

17

Dokumenttyp

Artikel i tidskrift

Förlag

American Physical Society

Ämne

  • Natural Sciences
  • Physical Sciences

Status

Published

ISBN/ISSN/Övrigt

  • ISSN: 1098-0121