Effect of the metal-to-wire ratio on the high-frequency magnetoimpedance of glass-coated CoFeBSi amorphous microwires

• Published in: Sensors and actuators. A. Physical. 2008-04, Vol.142 (2), p.533-537
• Main Authors: Valenzuela, R., Fessant, A., Gieraltowski, J., Tannous, C.
• Format: Article
• Language: English
• Subjects: Amorphous magnetic wires; Giant magnetoimpedance; Magnetic anisotropy; Magnetostriction
• ISSN: 0924-4247; 1873-3069
• DOI: 10.1016/j.sna.2007.05.006

High-frequency [1–500 MHz] measurements of the magnetoimpedance (MI) of glass-coated Co 69.4Fe 3.7B 15.9Si 11 microwires are carried out with various metal-to-wire diameter ratios. A twin-peak, anhysteretic behaviour is observed as a function of magnetic field. A maximum in the normalized impedance, Δ Z / Z , appears at different values of the frequency f, 125, 140 and 85 MHz with the corresponding diameter ratio p = 0.80 , 0.55 and 0.32. We describe the measurement technique and interpret our results with a thermodynamic model that leads to a clearer view of the effects of p on the maximum value of MI and the anisotropy field. The behavior of the real and imaginary components of impedance is also investigated; they display a resonance that becomes a function of the dc field H dc for values larger or equal to H K the circumferential anisotropy field for each p value. These results are interpreted in terms of a rotation model of the outer shell magnetization.