The frequency dependent low-field circular ac susceptibility = ′ -j ″ of a nearly nonmagnetostrictive Co68.2 Fe4.3 Si12.5 B15 amorphous wire annealed at 470 °C is determined by impedance Z measurements under stepwise decreased longitudinal dc field Hdc from 216 to -216 A/m after premagnetization at 16 kA/m. It is found that compared with the results of the classical eddy-current model, the measured low-frequency loss factor is larger by an anomaly factor between 1.5 and 3, depending on the value of Hdc. However, the (f) curve at each value of Hdc may be well fitted by an eddy-current model of bamboo-domain wall displacements if the material conductivity is replaced by a greater effective one and a proper value of effective domain size is chosen. The physical mechanism of such a fitting is discussed based on previous studies on anomalous dc circular susceptibility. This anomalous (f, Hdc) leads to an anomalous magnetoimpedance Z (Hdc) with a two-peak feature when frequency is high. © 2008 American Institute of Physics.