Magnetization distribution of 180° domain walls at the surface of 3% Si–Fe sheets

The surface magnetic domain structure of 100μm thick 3% Si–Fe sheets was imaged by using a scanning electron microscope with polarization analysis (SEMPA) in ultra-high vacuum. Two orthogonal in-plane components of the secondary electron spin polarization were measured to obtain the surface magnetic microstructure. Using a calibration sample, we have determined that our spatial resolution varies between 150 and 250nm depending on the experimental conditions. The 3% Si–Fe sheets have undergone tertiary recrystallization and have uniaxial anisotropy. At the center, the samples are composed of 180° stripe domains ((110) texture). High-magnification SEMPA images show that the magnitude of the in-plane magnetization vanishes at the domain walls. The width of the observed domain walls is approximately 400nm on the same samples. In order to confirm that the magnetization is out-of-plane in the domain walls, SEMPA measurements were performed with the sample tilted around the horizontal axis. It was observed that the out-of-plane component of the magnetization is projected onto the sample plane. With increasing tilt angle, line scans taken from corresponding SEMPA images clearly show that the in-plane component of magnetization at the domain walls increases. This is the first observation of out-of-plane magnetization at a surface domain wall.