Optical characterization of in-plain spin texture in 10-nm-scale Neel-type magnetic domain wall

We present that dark-field longitudinal magneto-optical Kerr effect (MOKE) microscopy can visualize the in-plain spin texture of the subwavelength-scale Neel-type magnetic domain wall. Conventional MOKE microscopy has never resolved the spin texture at the nanoscale due to not only the optical diffraction limit but also extremely small magneto-optic (MO) susceptibility. The dark-field illumination isolates the MOKE signal of the domain wall from those of the magnetic domains effectively with a high signal-to-background ratio. Also, we employed a perfect optical absorption multilayer to vanish the non-MO signals dramatically and boost the measurement efficiency. We examined the Neel-type magnetic domain wall of the Pt/Co/Pt/Ta film and measured its MO scattering width to be ~9.14 pm, experimentally. The intensity of the longitudinal MOKE signal from the domain wall depends on the orientation of in-plane magnetization relative to the azimuthal angle of incidence. Angle-dependent, precise measurement of the longitudinal MOKE scattering enables us to identify spatial magnetization distribution along the 10-nm-scale magnetic domain wall. We expect our work will offer a new possibility in research on complex in-plane spin textures such as vertical Bloch lines and skyrmions.