Exchange interaction through amorphous intergranular layers in a two-phase system

Amorphous melt spun ribbons of composition Fe87.2 Zr7.4 B4.3 Cu1.1 have been annealed at temperatures between 713 K and 923 K, achieving different stages of the nanocrystallization process. The sample annealed at 748 K shows a large magnetic hardening at room temperature as well as an irregular domain pattern. Both are attributed to the presence of non-coupled crystallites. When cooled to 250 K, the coercivity of this sample decreases steeply as the crystallites become coupled. The samples as cast and annealed at higher temperatures are magnetically soft and show wide regular domains. The above mentioned results as well as the thermal dependence of the coercivity are qualitatively described in the framework of a previously proposed model that accounts for the effective anisotropy in two-phase nanocrystalline materials.