Third and Fourth Order Phase Transitions: Exact Solution for the Ising   Model on the Cayley Tree
  An exact analytical derivation is presented, showing that the Ising model on the Cayley tree exhibits a line of third order phase transition points, between temperatures $T_2=2k_B^{-1}J\ln ({\sqrt 2}+1) $ and $T_{BP}=k_B^{-1}J\ln (3)$, and a line of fourth order phase transitions between $T_{BP}$ and $\infty$, where $k_B$ is the Boltzmann constant, and $J$ is the nearest-neighbor interaction parameter. 
Borko D. Stosic, Tatijana Stosic and Ivon P. Fittipaldi