Regensburg 2010 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 33: Poster II
MA 33.26: Poster
Freitag, 26. März 2010, 11:00–14:00, Poster B1
Superparamagnetism of Co/Pt nanodots with perpendicular anisotropy — •Alexander Neumann1, Simon Hesse1, André Kobs1, Andreas Frömsdorf2, and Hans Peter Oepen1 — 1Institut für Angewandte Physik, Universität Hamburg, Jungiusstr. 11, 20355 Hamburg, Germany — 2Institut für Physikalische Chemie, Universität Hamburg, Grindelallee 117, 20146 Hamburg, Germany
In this paper we present measurements of the magnetic behavior of Co/Pt nanodots with a mean diameter and a mean distance of 19 nm/90 nm, respectively. The dots were fabricated from Co/Pt multilayers using SiO2 particles as a shadow mask for Ar+ sputtering at 500 eV. The nanodots exhibit an easy axis of magnetization that is perpendicular to the substrate surface [1].
We studied the temperature dependence of the hysteresis loops of nanodots made from single and double Co/Pt bilayer with Co thickness of 7 Å within the range of 80 K to 325 K. The magnetization curves are determined by means of the extraordinary Hall effect (EHE). To determine the blocking temperature TB we used the temperature dependence of the coercive field. In case of the single Co/Pt bilayer nanodot a maximum of the ac-susceptibility is found that shifts to higher temperatures on frequency increase. From the results we calculated the nanodots switching time τ0.
[1] H. Stillrich et al., Adv. Funct. Mat. 18, p76-81, (2008).