Extraordinary eddy-current anomaly in nanocrystalline FeCuNbSiB wires under circular ac magnetization

The circular ac susceptibility of nanocrystalline FeCuNbSiB wire devitrified from its amorphous precursor by tension-current annealing is determined from ac impedance measurements. The results are shown to be well fitted by an eddy-current model of bamboo-domain wall displacements, but the frequency scale of the modeling curves has to be divided by a number 1. In contrast to the well-known eddy-current anomaly resulting from the existence of large domains, this eddy-current anomaly is extraordinary and originates from the presence of dispersed micromagnetic reversal regions within each domain, which exposes a remarkable feature of the magnetic structure of nanocrystalline materials. © 2006 American Institute of Physics.