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MA: Fachverband Magnetismus

MA 31: Surface Magnetism / Magnetic Imaging II

MA 31.1: Vortrag

Donnerstag, 25. März 2010, 15:15–15:30, H23

Theory of chirality selection in magnetic nanostructures: vortex states in magnetic nanodots — •Anna B. Butenko, Ulrich K. Rößler, and Alexei N. Bogdanov — IFW Dresden

Broken inversion symmetry at surfaces or interfaces of magnetic nanostructures induces Dzyaloshinskii-Moriya (DM) couplings. These chiral exchange couplings can essentially change the magnetic properties of nanostructures by stabilizing twisted magnetic states. In particular these DM couplings favour one sense of rotation in non-collinear magnetic configurations. Vortex states in magnetic thin film elements are chiral themselves, but they arise solely due to the demagnetization. In such magnetization structures, the effect of the chiral DM couplings is less obvious, but the degeneracy of the left- and right-handed vortices is lifted. Within a basic micromagnetic approach we analyse this chirality selection for the vortex ground states of circular thin-film elements. We calculate the differences between the core shapes and sizes of vortices with opposite handedness in the presence of DM couplings. These differences of the core structure may be observable in experiments, e.g., as differences in core diameter or net polarity of vortices, when switching their chirality. We suggest that such experiments can be used to determine the magnitude of surface-induced DM couplings in ultrathin magnetic films/film elements.