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Three-Dimensional Spin Fluctuations in Na0.75CoO2

L. M. Helme·A. T. Boothroyd·R. Coldea·D. Prabhakaran·D. A. Tennant·A. Hiess·J. Kulda
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Abstract

We report polarized- and unpolarized-neutron scattering measurements of magnetic excitations in single-crystal Na0.75CoO2. The data confirm ferromagnetic correlations within the cobalt-layers and reveal antiferromagnetic correlations perpendicular to the layers, consistent with an A-type antiferromagnetic ordering. The magnetic modes propagating perpendicular to the layers are sharp, and reach a maximum energy of ~12 meV. From a minimal spin wave model, containing only nearest-neighbour Heisenberg exchange interactions, we estimate the inter- and intra-layer exchange constants to be 12.2 +/- 0.5 meV and -6 +/- 2 meV, respectively. We conclude that the magnetic fluctuations in Na0.75CoO2 are highly three-dimensional.

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L. M. Helme, A. T. Boothroyd, R. Coldea, D. Prabhakaran, D. A. Tennant, A. Hiess, J. Kulda. 2004-10-19. Three-Dimensional Spin Fluctuations in Na0.75CoO2. https://doi.org/10.1103/physrevlett.94.157206

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