Sample Length Dependence of Giant Magnetoimpedance in FeCuNbSiB Nanocrystalline Ribbons

Abstract

In this work the sample length dependence of giant magnetoimpedance for Fe 73:5 Cu 1 Nb 3 Si 13:5 B 9 nanocrystalline ribbons was investigated. The longitudinal magnetoimpedance ÁZ=Z 0 for Fe 73:5 Cu 1 Nb 3 Si 13:5 B 9 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 ÁZ=Z 0 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 ¼ 40 mm, there is a maximum phenomenon of peak field H P at about 700 $ 900 kHz for shorter sample with L ¼ 13 mm. With increasing ac frequency, the peak-magnetoimpedance ðÁZ=Z 0 Þ p also experiences a maximum value for both longer and shorter samples. The maximum peak-magnetoimpedance ½ðÁZ=Z 0 Þ p max shifts to lower frequency with reduction of sample length.