Elementary excitations and phase transition in uniformly frustrated Heisenberg spin systems

A Green’s‐function method is used to study spin‐wave excitations and phase transition in a three‐dimensional uniformly frustrated Heisenberg spin system of simple cubic structure. The frustration is made to vary by changing the antiferromagnetic bond strength. We take into account different sublattices that result in gaps at the Brillouin zone boundaries in the spin‐wave spectrum. The sublattice order parameters as a function of temperature and the critical temperature are calculated self‐consistently. Comparison with Monte Carlo simulations performed by us is shown and discussed.