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mardi 26 mai 2009 — 14:00

Frustrated antiferromagnets with strong easy-axis anisotropy

Kedar Damle (Tata Institute, Mumbay)

par Pierre Pujol - 26 mai 2009

We consider S > 3/2 kagome and triangular lattice magnets with strong easy axis single-ion anisotropy D and antiferromagnetic exchange J. When D \gg J, the low energy states selected by the anisotropy map on to configurations of the corresponding classical Ising antiferromagnet. Sub-leading {\mathcal O}(J^3S/D^2) multi-spin interaction arising from the transverse quantum dynamics makes the low temperature behaviour very different from the well-known classical case : The kagome magnet goes into a semiclassical spin liquid state with distinctive and unusual short-range correlations below a crossover temperature T^{*} \approx 0.08J^3S/D^2, while the triangular magnet undergoes a first-order transition at T_c \approx 0.1 J^3 S/D^2 to an orientationally ordered collinear state that gives rise to a novel zero-magnetization plateau for small magnetic fields along the easy axis. Possible experimental implications are also discussed.