Magnetism and Magnetization Structure of c-Axis Oriented Single-Crystal Cobalt Films Grown Epitaxially on Rigid Underlayers

c -axis oriented, single-crystal, Co films were grown on mica using either Ti or Ru underlayers and exhibited the following crystallographic orientation relationship (00.1) mica y (00.1) underlayer y (00.1) Co , and [11.0] mica y [10.0] underlayer y [10.0] Co . Fundamental magnetic properties of the films were measured: H c ~ 4 kA/m, B s ~ 1.95 T, and K u ~ 5  10 5 J/m 3 . The as-grown magnetization structure of thinner ( t  30 nm) films shows mainly 180° domain walls with a uniform distribution of crossties, while thicker ( t = 60 nm) samples show stripe domains with a width of 75 nm. In spite of their excellent c -axis orientation (FWHM Co(002) ~ 1.5°), the effective anisotropy of these films is in-plane but with a small perpendicular magnetization component. These features in the hysteresis behavior are consistent with a simple noninteracting particle model incorporating the shape anisotropy of the small sized grains. For thinner samples the validity of this model has been verified by annealing experiments.