Antiphase resonance at X-ray irradiated microregions in amorphous Fe80B20 stripes

We report on the induction, through X-ray irradiation, of local anisotropy modifications in amorphous Fe80B20 stripes prepared by laser lithography from 15 nm thick films deposited by pulsed laser ablation. Those anisotropy modifications, taking place in a zone having a dimension of 15 mu m around the X-ray beam (2 mu m width) incidence area center point, lead to an effective transverse-to-the-stripe long axis local magnetic easy axis that can be exploited to stably localize a 180 degrees domain wall, in remanence after saturation with a transverse-to the stripe easy axis fie field. Upon stabilizing that wall it is possible to excite spatially inhomogeneous ferromagnetic resonances nearby the irradiated region (IR). The time dependencies of the magnetization precession at both sides of the IR exhibit a uniform phase shift of 180 degrees over distances of the order of 20 mu m from the stabilized domain wall.