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Helical magnets support topologically stable excitations characterized by a full twist of the magnetization on a length scale determined by spin-orbit coupling. Such magnetic whirls are known as Skyrmions, originally conceived by Tony Skyrme in a different context to model baryons. In the presence of a magnetic field, magnetic Skyrmions can even condense in the magnetic ground state forming a magnetic lattice similar as the vortex lattice in type II superconductors. Such a Skyrmion lattice has been recently identified by neutron scattering in MnSi. I give an overview of the helical magnet MnSi and report on recent spin-transfer torque experiments. The magnetization within the Skyrmion lattice phase can be manipulated upon applying an ultralow electric current, five orders of magnitudes smaller than those typically applied in experimental studies on current-driven magnetization dynamics on nanostructures. I explain the efficient spin-transfer torques arising from the coupling of spin currents to the magnetic whirls and discuss future perspectives.

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Markus Garst, Institut für Theoretische Physik, Universität Köln
Hörsaal 3
Contact: not specified