Regensburg 2010 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 17: Spin Dynamics / Spin Torque II

MA 17.2: Hauptvortrag

Mittwoch, 24. März 2010, 14:30–15:00, H10

Ultrafast switching of magnetic vortex cores – The role of the internal energy — •Riccardo Hertel — Institut für Festkörperforschung IFF-9, Forschungszentrum Jülich GmbH, Leo-Brandt-Str., D-52425 Jülich

The recently discovered dynamic switching of magnetic vortex cores can be regarded as the most complex fundamental micromagnetic switching process. It is mediated by the rapid formation and annihilation of vortex-antivortex pairs. The first observation of this core switching was obtained by varying the amplitude of an external field tuned at the gyrotropic resonance frequency [1]. This switching route is rather slow, since it requires several nanoseconds to resonantly excite a vortex from the equilibrium state up to the switching threshold. Alternatively, an ultrafast route has been proposed based on single, short field [2] or electric current [3,4] pulses which can switch the core within a few tens of picoseconds. In spite of these differences in switching times, simulations show that the micromagnetic process of the core reversal is the same for both routes. With our finite-element code we studied the role of the internal energy in these processes. We find that the vortex core always switches at well-defined energy thresholds. Careful analysis of the mesh-size dependence of the computed values shows that the critical switching energy is in agreement with the analytic value for the formation energy of a vortex-antivortex pair. [1] B. Van Waeyenberge et al., Nature 444, 461 (2006) [2] R. Hertel et al., Phys. Rev. Lett. 98, 117201 (2007) [3] K. Yamada et al., Nature Mater. 6, 270-273 (2007) [4] Y. Liu et al., Appl. Phys. Lett. 91, 112501 (2007)