Random Bond Ising Model
Disorder-induced Griffiths phase and shifted critical temperature
M = — | T_c (clean) = 2.269
2D Ising with random bonds J_ij ∈ [J-Δ, J+Δ]. Weak disorder (Δ small): T_c shifts slightly, transition
remains sharp. Strong disorder (Δ→1): Griffiths phase — rare strongly-coupled clusters stay ordered
above T_c, creating non-analytic free energy. Left: spin configuration. Right: magnetization vs T curve
(blue = current disorder, orange reference = clean Ising).