Field-dependent surface impedance tensor in amorphous wires with two typesof magnetic anisotropy: Helical and circumferential - art. no. 144424

This paper concerns the theoretical and experimental investigation of the m agnetoimpedance (MI) effect in amorphous wires in terms of the surface impe dance tensor (sic). Physical concepts of MI and problems of significant pra ctical importance are discussed using the results obtained. The theoretical analysis is based on employing the asymptotic-series-expansion method of s olving the Maxwell equations for a ferromagnetic wire with an ac permeabili ty tensor of a general form associated with magnetization rotation. The mag netic-structure-dependent impedance tensor (sic) is calculated for any freq uency and external magnetic field, and is not restricted to the case when o nly strong skin effect is present. This approach allows us to develop a rig orous quantitative analysis of MI characteristics in wires, depending on th e type of magnetic anisotropy, the magnitude of de bias current, and an exc itation method. The theoretical model has been tested by comparing the obta ined results with experiment. For the sake of an adequate comparison, the f ull tensor (sic) is measured in CoFeSiB and CoSiB amorphous wires having a circumferential and helical anisotropy, respectively, by determining. the S -21 parameter. In cases when the rotational dynamics is responsible for the impedance behavior, then is a reasonable agreement between the experimenta l and theoretical results. Such effects as the ac biased asymmetrical MI in wires with a circumferential anisotropy, and the transformation in MI beha vior caused by a de current (from that having a symmetric hysteresis to an asymmetric anhysteretic one) in wiles with a helical anisotropy are discuss ed.