Current-induced oscillations of a Bloch wall in magnetic thin films

An electric current traversing a domain wall induces an S-shaped distortion of the wall, in a ferromagnetic film with in-plane magnetization such as Ni-Fe. We calculate the degree of ac wall distortion as a function of current intensity and frequency, for sinusoidal ac drive current. The degree of wall distortion exhibits a maximum for exciting frequencies close to a certain resonance frequency similar or equal to 10-100 MHz. We predict the resonance frequency as a function of film thickness. The oscillating wall distortion causes a reduction of the coercive field of the material, also maximum near the resonance frequency. Finally, the complex electrical impedance of a sample containing many parallel walls also exhibits a resonance at that frequency.