SPIN-ENHANCED ORDERING IN FULLY FRUSTRATED ISING-MODELS

The fully frustrated triangular antiferromagnetic Ising model is found to order for higher spin values at finite temperatures. The ordered s ublattices exhibit unsaturated magnetizations down to zero temperature , except for S = infinity, which saturates. These results are obtained by the recently developed hard-spin mean-field theory, which is highl y successful for frustrated systems. The S = 1/2 case, as expected, an d the S = 1 case show no finite-temperature ordering. Thus, ordering b ehavior is enhanced with increased spin values, in contrast to ferroma gnetic systems.