MAGNETIC-FIELD-INDUCED 1ST-ORDER TRANSITION IN THE FRUSTRATED XY MODEL ON A STACKED TRIANGULAR LATTICE

The results of extensive Monte Carlo simulations of magnetic-field-ind uced transitions in the XY model on a stacked triangular lattice with antiferromagnetic intraplane and ferromagnetic interplane interactions are discussed. A low-field transition from the paramagnetic to a thre e-state (Potts) phase is found to be very weakly first order with beha vior suggesting tricriticality at zero field. In addition to clarifyin g some long-standing ambiguity concerning the nature of this Potts-lik e transition, the present work also serves to further our understandin g of the critical behavior at T(N), about which there has been much co ntroversy.