Abstract
The circular susceptibility of axially magnetized, nearly non-magnetostrictive Co–Fe–Si–B amorphous wires can have qualitatively different behaviour from and be up to 55 times greater than what is expected by standard domain magnetization rotations theory. This may be caused by intrinsic and annealing-induced soft and hard magnetic inclusions embedded in the soft magnetic matrix; when the spontaneous magnetization of the inclusions is greater than that of the matrix pointing in the same axial direction, exchange-coupled disc-like soft magnetic structures form and they may hugely enhance the circular magnetization. Our results provide a sensitive tool to probe the structures in amorphous wires and suggest an important factor to consider in the study of giant magneto-impedance.