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Relationship between Nonadiabaticity and Damping in Permalloy Studied by Current Induced Spin Structure Transformations

2008; American Physical Society; Volume: 100; Issue: 6 Linguagem: Inglês

10.1103/physrevlett.100.066603

1092-0145

L. Heyne, Mathias Kläui, D. Backes, T. A. Moore, S. Krzyk, U. Rüdiger, L. J. Heyderman, Arantxa Fraile Rodríguez, F. Nolting, Tevfik Onur Menteş, Miguel Ángel Niño, Andrea Locatelli, K. Kirsch, R. Mattheis,

Physics of Superconductivity and Magnetism

By direct imaging we determine spin structure changes in Permalloy wires and disks due to spin transfer torque as well as the critical current densities for different domain wall types. Periodic domain wall transformations from transverse to vortex walls and vice versa are observed, and the transformation mechanism occurs by vortex core displacement perpendicular to the wire. The results imply that the nonadiabaticity parameter beta does not equal the damping alpha, in agreement with recent theoretical predictions. The vortex core motion perpendicular to the current is further studied in disks revealing that the displacement in opposite directions can be attributed to different polarities of the vortex core.