Giant Magnetoimpedance in As Cast Fe₈₄Nb_3.5Zr_3.5B_9−xCu_x Ribbons

Abstract

In the present work the giant magnetoimpedance of Fe₈₄Nb_3.5Zr_3.5B_9−xCu_x as cast ribbons was reported. With increasing Cu content, the magnetoimpedance increases at first, experiences a maximum value at about x=3, and then decreases again at high Cu content. The value of magnetoimpedance ΔZ⁄Z₀=(Z(H)−Z(0))⁄Z(0) for Fe₈₄Nb_3.5Zr_3.5B₆Cu₃ (x=3) as cast ribbon is −37.5% under H=7162 A/m at 700 kHz. The large magnetoimpedance for Fe₈₄Nb_3.5Zr_3.5B₆Cu₃ is connected with the strong change of transverse permeability. The grain size of α-Fe derived from (200) peak based on Scherrer’s equation is 19 nm for Fe₈₄Nb_3.5Zr_3.5B₆Cu₃ (x=3), 13 nm for Fe₈₄Nb_3.5Zr_3.5B₅Cu₄ (x=4) and 11 nm for Fe₈₄Nb_3.5Zr_3.5B₄Cu₅ (x=5), respectively. The high Cu addition in Fe-(Nb,Zr)-B-Cu not only enhances the nucleation of α-Fe in as cast ribbon, but also reduces its grain size. The present experimental results indicated that Fe-(Nb,Zr)-B-Cu nanocrystalline materials with large magnetoimpedance can be fabricated with melting-spinning method without annealing.