Phase transition in the randomly diluted triangular-lattice antiferromagnet with single-ion anisotropy in an external field

The Heisenberg antiferromagnetic triangular lattice with inter-layer coupli ng and single-ion anisotropy is investigated by employing an alternative Gr een function decoupling procedure. The obtained anomalies of correlation fu nction and specific heat demonstrate that there exist two phase transitions . The spin order is proposed to be open-umbrella-like, Ising-like or parama gnetic structure in the different phases. (C) 2000 Published by Elsevier Sc ience B.V. All rights reserved.