The Neel order for a frustrated antiferromagnetic Heisenberg model: beyondlinear spin-wave theory

Within Dyson-Maleev (DM) transformation and self-consistent mean-field trea tment, the Neel order/disorder transition is studied for an antiferromagnet ic Heisenberg model which is defined on a square lattice with a nearest nei ghbour exchange J(1) and a next-nearest neighbour exchange J(2) along only one of the diagonals. It is found that the Neel order may exist up to J(2)/ J(1)= 0.572, beyond its classically stable regime. This result qualitativel y improves that from linear spin-wave theory based on Holstein-Primakoff tr ansformation. (C) 2000 Elsevier Science B.V. All rights reserved.