FAST SWITCHING BEHAVIOUR OF NANOSCOPIC NiFe- AND Co-ELEMENTS J. Fidler, T. Schrefl, V.D. Tsiantos, W. Scholz and D. Suess Institute of Applied and Technical Physics, Vienna University of Technology Wiedner Hauptstr. 8-10, A-1040 Vienna, Austria Abstract Three-dimensional micromagnetic simulations were performed to study the magnetisation reversal processes of granular nanoelements using a hybrid finite element/boundary element model. Transient magnetisation states during switching are investigated numerically in granular, thin Ni 80 Fe 20 and Co square shaped nanoelements (100 x 100 nm 2 ) with 10 nm grain size and a thickness of 10 nm and taking into account a random orientation of the grains. Switching dynamics are calculated for external fields between 80 kA/m and 280kA/m, which were uniformly applied after a rise time of 0.05 and 0.1 ns, respectively, and in comparison for a 10 GHz rotational field. Reversal in the unidirectional field proceeds by the nucleation and propagation of end domains towards the centre of the granular thin film elements. The formation of a vortex magnetisation structure leads to an increase of the switching time in the granular Co element. The switching time strongly depends on the Gilbert damping parameter α. Small values of α (≤ 0.1) lead to shorter switching times at small field strength values (h < 0.5 J s /µ 0 ). Reversal in rotational fields involves inhomogeneous rotation of the end domains towards the rotational field direction leading to partial flux-closure structures and therefore facilitating the switching by reduced switching times. The micromagnetic study reveals that