Barkhausen avalanches in anisotropic ferromagnets with 180 degrees domain walls

We show that Barkhausen noise in two-dimensional disordered ferromagnets wi th extended domain walls is characterized by the avalanche size exponent ta u(s)=1.54 at low disorder. With increasing disorder the characteristic doma in size is reduced relative to the system size due to nucleation of new dom ains and a dynamic phase transition occurs to the scaling behavior with tau (s)=1.30. The exponents decrease at finite driving rate. The results agree with recently observed behavior in amorphous Metglas and Fe-Co-B ribbons wh en the applied anisotropic stress is varied.