SINGULARITY OF THE SPECIFIC-HEAT OF 2-DIMENSIONAL RANDOM ISING-MODELS

The singularity of the specific heat is studied for the dilution (J > J' > 0) type and Gaussian type random Ising models using the Pfaffian method numerically. The type of singularity at the paramagnetic-ferrom agnetic phase boundary is studied using the standard regression method using data up to 600 x 601 system size. It is shown that the logarith mic type singularity is more reliable than the double-logarithmic type and cusp type singularities. The critical temperatures are estimated accurately for both the dilution type and Gaussian type random Ising m odels. A phase diagram relating strength of the randomness and tempera ture is also presented.