Frequency dependence of giant magnetoimpedance effect in CuBe/CoFeNi plated wire with different types of magnetic anisotropy

A giant magnetoimpedance effect (GMI) has been measured in a CuBe 0.1 mm diameter wire, electroplated with a ${\mathrm{Co}}_6{\mathrm{Fe}}_{20}{\mathrm{Ni}}_{74}$ layer 1 μm thick. Heat treatments after the electrodeposition were performed under the dc or ac field. The GMI has been measured in the frequency range 0.25 to 9 MHz, using ac driving current from 5 to 35 mA. The maximum GMI ratio depends strongly on the heat treatments, the intensity and the frequency of the driving current, reaching the value of 165% for optimal conditions. Results are discussed, taking into account the anisotropy distribution in the magnetic layer induced by the heat treatments under the field and a simple rotation model.