Regensburg 2004 – scientific programme

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MA: Magnetismus

MA 26: Mikro- und nanostrukturierte Materialien

MA 26.8: Talk

Thursday, March 11, 2004, 17:00–17:15, H10

Switching of single domain circular Permalloy dots observed by electron holography — •Martin Heumann and Josef Zweck — Universität Regensburg, Institut für Experimentelle und Angewandte Physik, 93040 Regensburg

The switching behavior of deep submicron circular Permalloy nanomagnets fabricated by electron beam lithography has been investigated. The specimens were observed using a transmission electron microscope. Holographic imaging provides sufficient magnetic resolution to observe the switching of single nanodots with diameters down to 80nm at a thickness of 6nm.

Permalloy dots of some hundred nanometers in diameter show a vortex magnetization scheme in remanence while with decreasing size and thickness a single domain magnetization scheme is expected to be energetically more favorable. Theoretical considerations lead to a phase-transition-like behavior.

Particles with about 100nm diameter and 6nm film thickness are expected to be in a single domain state. The experiment shows a single domain state during the whole switching process which takes place at external fields of only a few Oerstedt.

For slightly larger and thicker particles (e.g. 160nm diameter and 8nm thickness) the magnetization reversal runs via the formation of a c-state. But no vortex is formed either.