Micromagnetic Theory of Phase Transitions in Inhomogeneous Ferromagnets. V. Magnetic Phase Transition of Amorphous Fe10Ni70B16P4

The static magnetization curves and the dc susceptibility of amorphous Fe10Ni70B16P4 are measured in the low temperature region and in the vicinity of the critical region up to fields of μ0H = 1 T. The behaviour near the Curie temperature is found to obey critical material laws with critical indices: β = 0.44 ± 0.02; γ = 1.63 ± 0.07; δ = 4.82 ± 0.20, and the ferromagnetic Curie temperature TC = (191.1 ± 0.1) K. The critical indices satisfy the static scaling law γ = β(δ – 1). The exponent γ is found to apply over a wide temperature range of T – TC ± 100 K. The existence of this extended critical region is attributed to the correlation between temperature dependent spin clusters and the static fluctuations of the exchange interactions.