EN
The double-peak behaviour of giant magneto-impedance (GMI) dependence on the external magnetic field strength H is observed in as-cast glass-covered amorphous thin wire Co_{70.5}Fe_{4.5}Si_{15}B_{10} (microwire), as well as in microwire with the removed glass cover. The position of sharp peaks is symmetrical (H=± H_{m}) with respect to zero external magnetic field strength (H=0) and corresponds to the critical field of irreversible magnetization rotation. The maximum GMI ratio (ΔZ/Z)_{max} dependence on the amplitude of current i_{ac} at frequency of 1 MHz is analysed by means of the helical anisotropy (0<α<90°), induced during preparation of the microwire and after glass-cover removing. The additional dc bias current i_{dc} ≤ i_{ac} is applied in order to achieve asymmetrical GMI effect. Asymmetrical GMI dependences exhibit hysteresis which can be explained by irreversible magnetization rotation at ferromagnetic surface of the microwire.