Dresden 2003 – wissenschaftliches Programm

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MA: Magnetismus

MA 18: Spindynamik / Ummagnetisierungsvorg
änge

MA 18.9: Vortrag

Mittwoch, 26. März 2003, 17:15–17:30, HSZ/401

Localized reversal modes in Nickel nanowires — •Riccardo Hertel and Jürgen Kirschner — Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, 06120 Halle

Arrays of elongated magnetic nanoparticles are promising candidates for ultra-high density storage media. Besides the storage density, the magnetization reversal speed in such particles is an important parameter. We present studies on the magnetization reversal in Nickel nanowires of different thickness and shape which are exposed instantaneously to an external field of 200 mT. The investigations are performed using finite-element micromagnetic modelling based on the Landau-Lifshitz-Gilbert equation. The reversal dynamics in nanowires depends sensitively on the wire thickness. The wires’ length is 1µm, their thickness is between 30 and 60 nm. Within this thickness range, two fundamentally different reversal types are observed. In thin wires, a one-dimensional domain wall is nucleated which propagates slowly along the wire in a spiraling motion. In thicker wires, a localized curling-type reversal is found, which involves the formation and propagation of a micromagnetic singularity (Bloch point). The latter reversal type is about one order of magnitude faster than in thin wires (about 0,7 ns vs. 9,5 ns assuming a Gilbert damping of α=0,1). We study several details of this vortex-like magnetization reversal front which arise from the different mobility of the Bloch point and the surrounding vortex. A spontaneous mode-conversion is observed in a cone-shaped particle when the reversal front passes through a region of critical thickness, which in our example is at 42 nm.