  Domain structures in CoFeB-MgO thin films with a perpendicular easy
magnetization axis were observed by magneto-optic Kerr-effect microscopy at
various temperatures. The domain wall surface energy was obtained by analyzing
the spatial period of the stripe domains and fitting established domain models
to the period. In combination with SQUID measurements of magnetization and
anisotropy energy, this leads to an estimate of the exchange stiffness and
domain wall width in these films. These parameters are essential for
determining whether domain walls will form in patterned structures and devices
made of such materials.
