The surface spin spiral in the Fe double layer on W(110) is investigated within the framework of micromagnetic theory. It is shown that the previously suggested restriction to homogeneous spiral profiles and the consideration of the demagnetizing energy within the concept of an effective magnetic anisotropy do not allow for a consistent description of all experimental observations. After a detailed discussion of the model approaches in the literature, an extended micromagnetic model is proposed. The respective model parameters are derived as fit parameters to experimental data. It is shown that the presented model overcomes the deficiencies of all previous approaches. In particular, it reproduces the hitherto unexplained divergence of the spiral period in narrow Fe double-layer stripes of a width below 15 nm.

• Received 13 October 2011

DOI:https://doi.org/10.1103/PhysRevB.85.024420