S ep 2 00 4 Spin Dynamics of Layered Triangular Antiferromagnets with Uniaxial Anisotropy Ranjan Chaudhury

The spin dynamics of the semiclassical Heisenberg model with uniaxial anisotropy, on the layered triangular lattice with antiferromagnetic coupling for both intralayer nearest neighbor interaction and interlayer interaction is studied both in the ordered phase and in the paramagnetic phase, using the Monte Carlo-molecular dynamics technique. The important quantities calculated are the full dynamic structure function S(q, ω), the chiral dynamic structure function Schi(ω), the static order parameter and some thermodynamic quantities. Our results show the existence of propagating modes corresponding to both S(q, ω) and Schi(ω) in the ordered phase, supporting the recent conjectures. Our results for the static properties show the magnetic ordering in each layer to be of coplanar 3-sublattice type deviating from 120 degree structure. In the presence of magnetic trimerization however, we find the 3-sublattice structure to be weakened alongwith the tendency towards noncoplanarity of the spins.