Study of magnetoimpedance effect of Co-based amorphous ribbons after current annealing at various kinds of ambient pressure

The physical properties of magnetic amorphous alloys can be improved by using different annealing processes. In this paper, for annealing purposes, different driving currents were flowed through Co-based magnetic amorphous ribbons at different ambient air pressures between 5 x 10(-5) mbar and 10(3) mbar. The magnetoimpedance effect in the annealed samples was studied at a frequency interval between 250 kHz and 10 MHz. Magnetic properties and microstructures of samples were investigated by means of alternative gradient force magnetometers and X-ray diffraction. Regarding the giant magnetoimpedance (GMI) effect, annealing at different ambient pressures with the same current can lead to various responses. For annealing at higher pressures such as in air, higher current is necessary for crystallization of samples which results in the development of greater transverse magnetic anisotropy. (C) 2009 Elsevier B.V. All rights reserved.