Determination of twist and charge of Bloch lines by direct optical observation

The magnetization twist and charge of vertical Bloch lines (VBL) in stripe-domain walls in ferrimagnetic garnet films have been investigated using a polarizing light microscope. The illuminating light path was modified to obtain a polarized, one-sided, dark field illumination. Bloch lines are identified as dark or white spots on a stripe domain wall, which appears as a bright line on a dark background. The twist and charge of Bloch lines are verified by their dynamic reaction (i.e. the direction of displacement) to in-plane and bias field pulses and correlated with the type of spot.<>