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 γ(T) the characteristic non‐monotonic temperature dependence is observed as predicted by the correlated molecular field theory.