Material considerations for vertical Bloch lines direct observation and dynamical study

The authors report on a materials growth study undertaken to clarify the origin of vertical Bloch lines contrast by direct optical observation in dark field on bubble garnet samples. The authors´ initial guess (a large Faraday rotation) was shown to be incorrect. Rather, the influence of a low quality factor (the ratio of uniaxial energy constant to the demagnetizing energy) was detected. This agrees with a model wherein the wall tilts out of the vertical plane, at the line position. A control of lines observation is thus possible. The authors demonstrate it for specific samples grown to be put in a bias field gradient system stabilizing one single wall