Observation of asymmetric Bloch walls in epitaxial Co films with strong in-plane uniaxial anisotropy

Combined studies involving magnetic force microscopy and micromagnetic simulations are used to investigate the domain wall structure in epitaxial Co(1010) thin films with strong in-plane uniaxial magneto-crystalline anisotropy. This letter shows experimental evidence that, for such a system, the domain wall structure transforms from an asymmetric Bloch wall into an asymmetric Neel wall upon decreasing the film thickness from 100 to 20 nm. This transition occurs without cross-tie wall formation. Furthermore, it is found that from the four possible energetically equivalent asymmetric Bloch wall configurations, only two are stabilized along a single domain wall. For a given wall, the transition from one configuration to the other involves the simultaneous reversal of the polarity of the Bloch core and the Neel cap.