Giant magnetoimpedance, skin depth, and domain wall dynamics

An analysis of the skin depth in CoFeBSi amorphous ferromagnetic wires, as a function of frequency, is presented, by using the quasi-static value of permeability measured at 100 Hz. At about 30 kHz, the skin depth becomes comparable to the wire´s radius (62.5 μm), which leads to a separation of the giant magnetoimpedance mechanism: domain wall movements for lower frequencies, and spin rotation for higher frequencies. For the latter, ferromagnetic resonance has been observed, which is clearly consistent with the expected magnetization process. On the other hand, both the real and the imaginary parts of permeability (derived from impedance measurements) confirm the former mechanism.