Correlation among impedance, longitudinal permeability and circumferential permeability in Fe-based amorphous wires

A correlation is made among the impedance, the longitudinal permeability and the so called circumferential permeability in Fe-rich amorphous wires. The measurements of longitudinal permeability are made while an AC driving current is flowing through the wire for measuring the impedance components L and R. For particular combinations of the amplitude of the AC driving current, its frequency and the axial test field frequency, the longitudinal relative permeability achieves very high values (40-50 × 103) in comparison with those (1-2 × 103) measured in absence of the AC driving current. The circumferential permeability, deduced from the values of L and R, increases too but the increases are moderate in comparison with those of the longitudinal permeability and are favoured by torsional stresses. The results, discussed on the basis of the domain core-shell model, are ascribed to a coupling between the magnetization variations occurring in the outer shell of the wire and those occurring in the inner core due to the concomitant effect of the AC circular field and the AC axial field. © 2003 Elsevier Science B.V. All rights reserved.