Critical Properties of the Mixed Ising Ferromagnet

Aline Franco Siqueira, I. P. Fittipaldi

Bin‐Zhou Mi, Huai‐Yu Wang

Umberto Laino Fulco, Fernando Dantas Nobre, L. R. da Silva +1 more

Erhan Albayrak, Ali Yigit

Enaldo F. Sarmento, T. Kaneyoshi

Using the ferromagnetic stability condition, the phase diagram is investigated in a quenched bond-mixed Ising ferromagnet with a transverse field \(\varOmega\) on the square lattice. The fact that large families of critical lines for negative-bond mixture meet at a single point on the line of T =0 is found to be closely related with frustrations due to negative bond. However the effect of frustrations may be observed only for a small value of \(\varOmega\) on the relevant physical properties.

Julia M. Yeomans, Robin B. Stinchcombe

A real-space rescaling method is applied to the mixed, spin- 1 / 2 , Ising ferromagnet. Both bond and site disorder are considered where, respectively, bonds J A , J B or sites A, B occur with probabilities p, 1-p. For the bond-disordered case, critical curves are obtained for the square lattice for a range of alpha identical to J B /J A . Slopes at p=0,1 are in very good agreement with exact results previously obtained and T c (p- 1 / 2 ) agrees to within a few per cent with an exact result obtained by Fisch. For the more realistic site-disordered problem only the case where bond strengths are related by tanh J AA tanh J BB =tanh 2 J AB is considered. Critical curves are plotted for various alpha for the square and triangular lattices. The results agree well with exact limiting slopes available for the square lattice. Thermal, percolation and crossover exponents are also calculated for both the site- and bond-disordered cases.