Magnetoimpedance effect in CoFeNi plated wire with ac field annealing destabilized domain structure

Giant magnetoimpedance (GMI) behavior at 0.25 MHz has been studied for a composite wire consisting of a 1 mu m thick Co6Fe20Ni74 magnetic layer electroplated onto a 0.1 mm diam CuBe nonmagnetic wire. This has been done for as-deposited samples as well as after annealing under dc and ac axial magnetic fields. In the optimum conditions, a maximum GMI of 150% is achieved. The observed GMI hysteresis in the as-prepared state decreases for high driving current used to measure the MI itself. Such hysteresis, to be avoided in technological applications, is also very much reduced after ac field annealing. GMI characteristics are analyzed considering the domain-wall stabilization occurring after the annealing treatments. (C) 1999 American Institute of Physics. [S0021-8979(99)17208-6].