Magnetic ground-state phase diagram of a multiple-spin exchange model on the triangular lattice

Abstract

We investigated the ground state of a multiple-spin exchange model, which may describe magnetism of the solid 3 He layers adsorbed on graphite. The model contains four-spin exchange terms together with the conventional Heisenberg ones. Using the mean-field theory we found numerous ground-state phases with large numbers (up to 144) of sublattices. These phases replace the previously reported infinitely degenerate phase. A novel phase with 6-sublattice non-coplanar spin structure, where both vector and scalar chiral orders exist, appears between the 120° Néel and tetrahedral phases. This phase is replaced by a novel 12-sublattice phase under the magnetic field.