Spin dynamics of frustrated easy-axis triangular antiferromagnet 2H-AgNiO2 explored by inelastic neutron scattering

EM Wheeler, R Coldea, E Wawrzynska, T Sorgel, M Jansen, M Koza, J Taylor, P Adroguer, NSP Shannon

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Abstract

We report inelastic neutron-scattering measurements of the spin dynamics in the layered hexagonal magnet 2H-AgNiO2, which has stacked triangular layers of antiferromagnetically coupled Ni2+ spins (S=1) ordered in a collinear alternating stripe pattern. We observe a broad band of magnetic excitations above a small gap of 1.8 meV and extending up to 7.5 meV, indicating strongly dispersive excitations. The measured dispersions of the boundaries of the powder-averaged spectrum can be quantitatively explained by a linear spin-wave dispersion for triangular layers with antiferromagnetic nearest- and weak next-nearest-neighbor couplings, a strong easy-axis anisotropy, and additional weak interlayer couplings. The resulting dispersion relation has global minima not at magnetic Bragg wave vectors but at symmetry-related soft points and we attribute this anomalous feature to the strong competition between the easy-axis anisotropy and the frustrated antiferromagnetic couplings. We have also calculated the quantum corrections to the dispersion relation to order 1/S in spin-wave theory by extending the work of Chubukov and Jolicoeur [Phys. Rev. B 46, 11137 (1992)] and find that the presence of easy-axis anisotropy significantly reduces the quantum renormalizations predicted for the isotropic model.
Translated title of the contributionSpin dynamics of frustrated easy-axis triangular antiferromagnet 2H-AgNiO2 explored by inelastic neutron scattering
Original languageEnglish
Pages (from-to)014421-1 - 014421-4
Number of pages4
JournalPhysical Review B: Condensed Matter and Materials Physics
Volume79
DOIs
Publication statusPublished - Mar 2009

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    Wheeler, EM., Coldea, R., Wawrzynska, E., Sorgel, T., Jansen, M., Koza, M., Taylor, J., Adroguer, P., & Shannon, NSP. (2009). Spin dynamics of frustrated easy-axis triangular antiferromagnet 2H-AgNiO2 explored by inelastic neutron scattering. Physical Review B: Condensed Matter and Materials Physics, 79, 014421-1 - 014421-4. https://doi.org/10.1103/PhysRevB.79.104421