Sample Length Dependence of Giant Magnetoimpedance in FeCuNbSiB Nanocrystalline Ribbons

Abstract

In this work the sample length dependence of giant magnetoimpedance for Fe_73.5Cu₁Nb₃Si_13.5B₉ nanocrystalline ribbons was investigated. The longitudinal magnetoimpedance ΔZ⁄Z₀ for Fe_73.5Cu₁Nb₃Si_13.5B₉ nanocrystalline ribbons decreases with the decreasing of sample length L due to the demagnetization effects. The demagnetization field lowers the permeability, especially for the very shorter sample. The magnetoimpedance ΔZ⁄Z₀ experiences a peak under a field H_p due to the existence of transverse anisotropy. Different from the saturation behavior of H_p at high frequencies for longer sample with L=40 mm, there is a maximum phenomenon of peak field H_P at about 700∼900 kHz for shorter sample with L=13 mm. With increasing ac frequency, the peak-magnetoimpedance (ΔZ⁄Z₀)_p also experiences a maximum value for both longer and shorter samples. The maximum peak-magnetoimpedance [(ΔZ⁄Z₀)_p]_max shifts to lower frequency with reduction of sample length.