Giant magnetoimpedance effect in nanocrystalline Fe₇₄Si_xB_22-xCu₁Nb₃ ribbons

We investigated the magnetoimpedance (MI) effect for the soft magnetic nanocrystalline Fe₇₄Si_xB_22-xCu₁Nb₃(x = 4-18) alloys, and also the relationship between the magnetic properties and the MI effect. The annealing temperature dependence of the MI ratio corresponds to that of the permeability of longitudinal direction of the samples. However, the Si concentration dependence of the longitudinal permeability is different from that of the MI ratio. The maximum MI ratio and the highest field sensitivity for die sample with x = 16 after annealing at 570 °C for 1 h are 67% and 23*/Oe, respectively. The MI effect is affected by the magnetic uniaxial anisotropy which is along the longitudinal direction of the ribbon samples.