Element-selective investigation of domain structure in CoPd and FePd alloys using small-angle soft X-ray scattering

Recent optical pump-probe experiments on magnetic multilayers and alloys identified $\it{perpendicular}$ spin superdiffusion as one of possible mechanisms responsible for femtosecond magnetization dynamics. On the other hand, no strong evidence for the ultrafast $\it{lateral}$ spin transport has been reported, so far. To address this question, we studied magnetic domain structure of CoPd and FePd thin films using small-angle scattering of soft X-rays. By tuning the synchrotron-generated X-rays to the absorption edges of Fe or Co we recorded Fourier images of the magnetic domain structure corresponding to a chosen element. Applying $\it{in-situ}$ magnetic fields resulted in pronounced rearrangement of domain structure that was clearly observed in scattering images. Our analysis of both the stand-alone, as well as magnetically coupled CoPd/FePd layers provides insight into the formation of domains under small magnetic field perturbations and pave the way to better understanding of transient changes expected in magneto-dynamic measurements.