THE CRITICAL EXPONENT NU ALONG THE FERROMAGNETIC-NONFERROMAGNETIC PHASE-BOUNDARY IN THE 2-DIMENSIONAL +/- J-ISING MODEL

The value of the critical exponent nu of the two-dimensional +/- J Ising model along the ferromagnetic-nonferromagnetic phase boundary in the p-T plane (p is the concentration of +J bonds; T is the temperature) has been calculated by the use of the transfer matrix method and the Roomany-Wyld approximation for long strips with finite width (L x 10(5): L less-than-or-equal-to 18), and has been found to take almost constant value, 1.0, at temperature above the Nishimori line. By the same method, a lower bound of the critical concentration between paramagnetic phase and the random antiphase state (RAS phase) has been calculated at some temperature below the Nishimori line in the p-T plane.