# Dresden 2006 – wissenschaftliches Programm

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# MA: Magnetismus

## MA 10: Micromagnetism / Computational Magnetism

### MA 10.3: Vortrag

### Montag, 27. März 2006, 17:30–17:45, HSZ 401

**The Jacobs-Bean model of chains of magnetic spheres, revisited** — •Riccardo Hertel — Institut für Festkörperforschung,Forschungszentrum Jülich, D-52425 Jülich

The field-driven magnetization reversal in a chain of perfectly aligned magnetic nano-spheres is studied by means of micromagnetic simulations. The diameter of the Fe spheres is 10 nm, the spacing is 1 nm. Chains of different length (up to 20 spheres) have been simulated. The only coupling between the spheres is given by the magnetostatic dipole interaction. According to the analytical Jacobs-Bean (JB) model for chains of magnetic spheres [1], the reversal is expected to occur by means of an inhomogeneous, so-called fanning mode. While the principal predictions of the JB model are confirmed by the simulations, a number of interesting additional features are observed. According to the simulations, the reversal of each individual sphere is given by a precessional reorientation towards the external field. The phase of the precession of each sphere is non-trivially coupled to the phase of the other spheres. The inhomogeneous reversal mode is symmetric with respect to the central plane perpendicular to the chain axis, leading to qualitative differences depending on whether the number of spheres in the chain is even or odd. The reversal begins in the central part of the chain. This is in striking contrast to the case of magnetic nanowires of similar size, where magnetization reversal has been shown to start at the wire ends.

[1] I.S. Jacobs and C.P. Bean, Phys. Rev 100 (4) 1060 (1955)