Spin-polarized scanning tunneling microscopy study of 360 degrees walls in an external magnetic field

Spin-polarized scanning tunneling microscopy is employed to study the internal structure of 360degrees magnetic domain walls in ultrathin Fe nanowires prepared on W(110). They are formed by pairs of winding 180degrees walls in an increasing external magnetic field. Their width is governed by an equilibrium of exchange and Zeeman energy. In the relevant field range (Bgreater than or equal to50 mT) the demagnetizing energy contributes only indirectly via an increased wall width, i.e., a reduced effective anisotropy, and nonlocal effects are negligible.