Diameter dependence of the giant magnetoimpedance in hard-drawn CoFeSiB amorphous wires

The as cast CoFeSiB amorphous wire with 135 mum was drawn out to wires with diameters of 84, 64, and 40 mum, respectively. The magnetoimpedance of the hard-drawn wires were investigated in comparison with the as cast one. For the hard-drawn wire of diameter 64 mum, the magnetoimpedance ratio DeltaZ/Z(0) can reach 269.9\%. There is a transform of the domain structure from the inner core longitudinal to the circular in hard-drawn wires compared with the as cast one. The frequency dependence of the magnetoimpedance in longitudinal and transverse cases show that both circumferential and longitudinal axial anisotropies may depend on the radial distance from the axis of the wire. (C) 2002 American Institute of Physics