High frequency [1-500 MHz] measurements of the Magneto-Impedance (MI) of
glass-covered Co69.4​Fe3.7​B15.9​Si11​ 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 ΔZ/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.Comment: 5 pages and 6 figure