DOMAIN WALL RELAXATION EFFECTS AND MAGNETOIMPEDANCE IN AMORPHOUS WIRES

The frequency response of as-cast, amorphous ferromagnetic wires of nominal composition (Co_0.96Fe_0.04)_72.5B₁₅Si_12.5 was investigated in the 5 Hz-13 MHz frequency range, and 0.3 mA (RMS) ac current amplitude. By analyzing the complex impedance behavior, we show that circumferential domain walls in the wires exhibit relaxation phenomena very similar to other magnetic materials such as ferrites (with electrical resistivities larger by several orders of magnitude). The main source of impedance is therefore the inductance coupling between the circular ac field and the circumferential domains. Finally, it appears that microscopic eddy currents are more significant than macroscopic eddy currents (or the so called, skin-depth effect).