FERROMAGNETIC-NONFERROMAGNETIC PHASE-BOUNDARY ON THE 2-DIMENSIONAL +/-J ISING-MODEL

The ferromagnetic-nonferromagnetic phase boundary on the two-dimensional ±J Ising model in the p-T plane is determined by the use of the coherent-anomaly method (CAM) proposed by Suzuki, where p is the concentration of the +J bond, and Tthe temperature. The phase boundary below the Nishimori line has been found to be vertical at p=0.884±0.001 to the p-axis, which is consistent with the previous results obtained under the assumption of Suzuki's weak universality. The critical exponent γp(T) has also been determined along the phase boundary, which shows a crossover tendency. © 1990, THE PHYSICAL SOCIETY OF JAPAN. All rights reserved.