Baxter-Wu model in the presence of an external magnetic field

► Baxter-Wu model undergoes a 2nd order phase transition for H<0. ► Critical exponents α, β, ν and γ are calculated for H<0. ► A gap exists in the values of critical exponents near H=0. ► The critical point (0,Tc) is an irrelevant one while there is also a relevant one.