Effect of domain structure on the impedance of ferromagnetic wire with circumferential anisotropy

Circumferential domain structure contribution to the impedance of amorphous Co68.2Fe4.3Si12.5B15 ferromagnetic wire in a zero external field was measured in two cases. With as-cast wire, changes in the impedance caused by removal of the domain structure in remanent state were measured. Uniform helical anisotropy was induced in the wire by thermal treatment. An inhomogeneous magnetic field applied in a low axial field region caused the formation of a domain structure consisting of two circular domains separated by a single domain wall in this wire. Changes in the impedance caused by removal of this domain structure were measured. In both cases characteristic frequency dependence with a single maximum in the range 1-2 MHz was observed. It is probable that this typical shape originates predominantly from frequency dependence of domain wall oscillations. In the high frequency region, changes in volume magnetization distribution and thus also in transverse permeability can play a significant role. Interpretation based on a stray field generated by axial magnetization inhomogeneities is proposed.