Triangular and kagome antiferromagnets with a strong easy-axis anisotropy

Abstract

We consider S>3/2 kagome and triangular lattice magnets with strong easy-axis single-ion anisotropy D and antiferromagnetic exchange J. When D≫J, the low energy states selected by the anisotropy map onto configurations of the corresponding classical Ising antiferromagnet. Subleading O(J³S/D²) multispin interaction arising from the transverse quantum dynamics makes the low-temperature behavior 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^∗≈0.08J³S/D², while the triangular magnet undergoes a first-order transition at T_c≈0.1J³S/D² 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.