First direct optical observation of Bloch lines in bubble garnets

Magnetization inhomogeneities are observed by optical means in the walls of domains in bubble garnet films with perpendicular magnetization. Specific illumination conditions (scanned laser light, angular selection, dark field imaging) allowed for this achievement. Experiments using known wall states, static in-plane field and pulsed bias field indicate that the magnetic origin of these structures can be assigned to vertical Bloch lines (Neel segments in Bloch walls). A magnetooptical explanation of the observed contrasts is outlined.