SEMPA imaging of domain dynamics in amorphous metals

We show how scanning electron microscopy with polarization analysis (SEMPA) may be used to observe domain wall motion in amorphous ferromagnetic ribbons commonly used in transformer cores. SEMPA images were obtained from both the smooth, air side of the ribbon, as well as the rough, difficult to image, wheel side. Domain wall motion was studied under both quasi-static and low-frequency fields (4 Hz). The domain walls are observed to have a wide range of mobilities and are occasionally pinned by surface defects even in well-annealed samples. Irreproducible domain wall motion was also observed, but was not always obviously related to defects. This has significant implications for future attempts to use stroboscopic measurements in the study of wall mobility at higher frequencies.