Circular magnetization process of nanocrystalline wires as deduced from impedance measurements

The circular magnetization process of FeSiBCuNb amorphous and nanocrystalline wires has been followed by the impedance measurements as a function of the amplitude and the frequency of driving current. The domain structure and consequently, the magnetization process have been tailored by suitable thermal processing. The different circular coercivity mechanisms are deduced by analyzing the magnetic losses. We find that the coercivity is due to domain-wall pinning for wire with axial domain, while the coercivity is from domain nucleation for one with transverse domain structure. In addition, the influence of axially applied field H is different for wires with different domain structure. The application of tensile stress to a wire with positive magnetostriction can be taken as an axial induced anisotropy, which makes the circular permeability decrease and the coercivity increase. Finally, the influence of driving current frequency on the circular magnetization process has been also studied for the wire with transverse domain structure. The results indicate that the frequency effect is from the eddy-current damping. © 2005 American Institute of Physics.