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arXiv · 0902.0359

Critical Anisotropies of a Geometrically-Frustrated Triangular-Lattice Antiferromagnet

M. Swanson·J. T. Haraldsen·R. S. Fishman
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Abstract

This work examines the critical anisotropy required for the local stability of the collinear ground states of a geometrically-frustrated triangular-lattice antiferromagnet (TLA). Using a Holstein-Primakoff expansion, we calculate the spin-wave frequencies for the 1, 2, 3, 4, and 8-sublattice (SL) ground states of a TLA with up to third neighbor interactions. Local stability requires that all spin-wave frequencies are real and positive. The 2, 4, and 8-SL phases break up into several regions where the critical anisotropy is a different function of the exchange parameters. We find that the critical anisotropy is a continuous function everywhere except across the 2-SL/3-SL and 3-SL/4-SL phase boundaries, where the 3-SL phase has the higher critical anisotropy.

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M. Swanson, J. T. Haraldsen, R. S. Fishman. 2009-02-02. Critical Anisotropies of a Geometrically-Frustrated Triangular-Lattice Antiferromagnet. https://doi.org/10.1103/physrevb.79.184413

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