Effect of Fe-exchange-field penetration on the residual amorphous phase in nanocrystalline Fe₉₂Zr₈

The temperature dependence of hyperfine interactions has been studied by means of Mössbauer spectroscopy for rapidly quenched amorphous Fe₉₂Zr₈ in as-quenched and partially crystallized states. An analysis of the temperature dependence of the mean hyperfine field based on the molecular-field approximation showed that the Curie temperature of the residual intergranular amorphous phase (T^am_C) is 330±5 K, well above the maximum Curie temperature in amorphous Fe-Zr binary alloys (T*_C ≈ 280K). The difference of T^am_C-T*_C (ΔT^am_C≈50 K) cannot be attributed to the possible magnetovolume effect in the sample. The difference of ΔT^am_C could be explained by an enhancement of the molecular field by ∼50 T at 0 K, induced by the Fe exchange field penetrating from the bcc-Fe nanocrystallites.