Quasi-dislocation dipole-type defects and low coercivity of Fe-based soft magnetic glassy alloys

The density and the magnetization process of the melt-spun glassy Fe-(A1, Ga)-(P, C, B, Si) alloys have been investigated to clarify the origin of low coercivity (H_c) of the glassy alloys. The density differences (Δp_c) between the crystalline and the amorphous phases of the glassy alloys are much smaller than that of the ordinary amorphous alloys. An analysis of the magnetization process based on the law of approach to ferromagnetic saturation reveals that quasi-dislocation dipole (QDD)-type defects, which are formed by agglomeration of vacancy-type point defects in planar regions, are the main sources of elastic stress and their size is nearly independent of the alloy system. Since H_c originates from elastic stress of QDDs is proportional (Δp_c)^1/2, the origin of the low H_c of the Fe-(Al, Ga)-(P, C, B, Si) glassy alloys is the low density of QDDs which corresponds to low density of the domain-wall pinning centers.