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American Physical Society, Physical review B, 2(83)

DOI: 10.1103/physrevb.83.024405

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Spin dynamics, short-range order, and spin freezing inY0.5Ca0.5BaCo4O7

Journal article published in 2011 by J. R. Stewart ORCID, G. Ehlers, H. Mutka, P. Fouquet ORCID, C. Payen, R. Lortz
This paper is available in a repository.
This paper is available in a repository.

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Abstract

Y0.5Ca0.5BaCo4O7 was recently introduced as a possible candidate for capturing some of the predicted classical spin kagome ground-state features. Stimulated by this conjecture, we have taken up a more complete study of the spin correlations in this compound with neutron scattering methods on a powder sample characterized with high-resolution neutron diffraction and the temperature dependence of magnetic susceptibility and specific heat. We have found that the frustrated near-neighbor magnetic correlations involve not only the kagome planes but concern the full Co sublattice, as evidenced by the analysis of the wave-vector dependence of the short-range order. We conclude from our results that the magnetic moments are located on the Co sublattice as a whole and that correlations extend beyond the two-dimensional kagome planes. We identify intriguing dynamical properties, observing high-frequency fluctuations with a Lorentzian linewidth Γ⩽20 meV at ambient temperature. On cooling a low-frequency (~1 meV) dynamical component develops alongside the high-frequency fluctuations, which eventually becomes static at temperatures below T≈50 K. The high-frequency response with an overall linewidth of ~10 meV prevails at T⩽2 K, coincident with a fully elastic short-range-ordered contribution.