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 Co6Fe20Ni74 layer 1 mu m 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. (C) 2000 American Institute of Physics. [S0021-8979(00)57008-X].