Permeability and giant magnetoimpedance in Co₆₉Fe_4.5X_1.5Si₁₀B₁₅ (X=Cr, Mn, Ni) amorphous ribbons

The magnetoimpedance (MI) has been measured in the amorphous ribbons of the soft ferromagnetic alloy Co₆₉Fe_4.5X_1.5Si₁₀B₁₅ (X=Cr, Mn, Ni) as functions of frequency (f). For all of the three samples, at low frequency, f≤5 MHz, the MI ratio increases with increasing frequency, but the MI ratio decreases at high frequency, f≥5 MHz. The MI profiles are not changed at low frequency regions of f≤1 MHz in the amorphous ribbons. The MI ratio at high frequency of f=5 MHz becomes 57% in Co₆₉Fe_4.5Cr_1.5Si₁₀B₁₅, but the MI ratio becomes 30% in Co₆₉Fe_4.5Mn_1.5Si₁₀B₁₅ and Co₆₉Fe_4.5Ni_1.5Si₁₀B₁₅. The MI ratio at f=10 MHz becomes 45% in Co₆₉Fe_4.5Cr_1.5Si₁₀B₁₅ and the MI ratio becomes 23% in Co₆₉Fe_4.5Mn_1.5Si₁₀B₁₅ and Co₆₉Fe_4.5Ni_1.5Si₁₀B₁₅, respectively. The maximum values of field sensitivity are 2.7(X=Cr), 2.5(X=Mn), 2.2(X=Ni)%/Oe for f = 5 MHz.