Berlin 2012 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 39: Micro- and Nanostructured Magnetic Materials I
MA 39.10: Vortrag
Donnerstag, 29. März 2012, 12:00–12:15, EB 202
Temperature dependent switching of single superparamagnetic nanodots — •Alexander Neumann1, Carsten Thönnißen1, Simon Heße1, Andreas Meyer2, and Hans Peter Oepen1 — 1Institut für Angewandte Physik, Universität Hamburg, Germany — 2Institut für Physikalische Chemie, Universität Hamburg, Germany
We have investigated the temperature dependence of the coercive field and the time dependent switching behavior of single Co/Pt nanodots (<30nm) in the range of 80K to 300K. We used Sharrocks formula to determine from the coercivities the anisotropy constant K and the saturation magnetization MS [1]. Additionally, the anisotropy constant is determined from the temperature dependent switching behavior [2]. The magnetic volume V of the nanodots is determined directly from images taken by scanning electron microscopy. Both fittings give results that are identical within the error margin and slightly smaller than the film value. The time constant τ0 is considerably smaller than expected for a macro-spin behavior. The dots were fabricated out of thin Co/Pt film via Ar+ ion milling at 150eV utilizing SiO2 particles as a shadow mask. The Co/Pt film is tuned to give perpendicular anisotropy which is preserved in the nanodots [3]. Via a hall cross the state of magnitization is obtained by the anomalous Hall-Effect.
[1]M. P. Sharrock, IEEE Trans. Magn. 26, p193-197, (1990)
[2]Bean and Livingston, J. Appl. Phys. 30, 120S, (1959)
[3]H. Stillrich et al. Adv. Funct. Mat. 18, p76-81, (2008).