Dresden 2003 – wissenschaftliches Programm

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MA: Magnetismus

MA 20: Mikromagnetismus / Computational Magnetics

MA 20.2: Vortrag

Mittwoch, 26. März 2003, 17:45–18:00, HSZ/405

Effect of Lateral Confinement on fct-Ni(001) Perpendicular Media — •Jonathan Ha, Riccardo Hertel, and J. Kirschner — Weinberg 2, 06120 Halle, Germany

The Cu/Ni(t)/Cu(001) system has been known to exhibit out-of-plane and stripe domains in films of various thicknesses (2nm ≤ t ≤ 200nm). In this conference, we present a study on the effect of lateral confinement on the spin arrangement of the nickel layer using finite-element micromagnetic modeling. For simplicity, both the top and bottom Cu layers are assumed identical, although this assumption may not be realistic in experiments (Fukumoto et al., Surf. Sci. 514, 151 (2002)). The strain of the nickel — the main driving force for the observed perpendicular magnetization — is modelled to decrease with increasing nickel film thickness in accordance to a t^−2/3 law. The main message of our finding is that the geometric shape of the element can play a key role in determining the domain shape. For example, stable ring domain structure, that is, a magnetic state in which the domains arrange in concentric rings of alternating up and down magnetization, is observed in discs of different sizes (10nm ≤ t ≤ 30nm, 200nm ≤ d ≤ 400nm, where d is the disc diameter). We attribute this geometric effect to the non-local demagnetizing factor: the demagnetizing field is lower at the perimeter than at the disc center, resulting in an effective radial anisotropy through which the magnetization senses the boundary. Domains in other geometries such as rectangles and triangles have also been examined, and they also reflect the respective geometry of the element.