The magnetic phase transition in amorphous and disordered crystalline ferromagnets

The magnetic phase transition of amorphous FeNi-base alloys and disordered crystalline FeNi alloys is investigated, and the methods for a determination of the asymptotic critical exponents and the effective exponents are discussed critically. Two general results are obtained: 1) For the asymptotic exponents no significant deviations from the 3d-Heisenberg exponents are found. 2) For the effective susceptibility exponent ϒ(T) the characteristic non-monotonic temperature dependence is observed as predicted by the correlated molecular field theory