Magnetism and magnetization structure of c-axis oriented single-crystal cobalt films grown epitaxially on rigid underlayers

Abstract

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 ∥ (00.1)underlayer ∥ (00.1)Co, and [11.0]mica ∥ [10.0]underlayer ∥ [10.0]Co. Fundamental magnetic properties of the films were measured: Hc∼4 kA/m, Bs∼1.95 T, and Ku∼5×105 J/m3. 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 (FWHMCo(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.