Critical Behavior for 2d Uniform and Disordered Ferromagnets at   Self-Dual Points
  We consider certain two-dimensional systems with self--dual points including uniform and disordered $q$-state Potts models. For systems with continuous energy density (such as the disordered versions) it is established that the self--dual point exhibits critical behavior: Infinite susceptibility, vanishing magnetization and power law bounds for the decay of correlations. 
Lincoln Chayes, Kirill Shtengel