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MA: Fachverband Magnetismus
MA 3: Micro- and nanostructured Materials
MA 3.2: Vortrag
Montag, 7. März 2016, 09:45–10:00, H32
The influence of a temperature dependent anisotropy on the attempt frequency of single superparamagnetic nanodots — •Stefan Freercks1, Alexander Neumann1,2, Carsten Thönnißen1, André Kobs1,3, Eva-Sophie Wilhelm1, and Hans Peter Oepen1 — 1Institut für Nanostruktur- und Festkörperphysik, Universität Hamburg, Germany — 2Institut für Medizintechnik, Universität zu Lübeck, Germany — 3Deutsches Elektronen-Synchrotron (DESY), Hamburg, Germany
We have developed a feasible method to study the magnetization behavior of single nanodots with an anisotropy perpendicular to the film plane utilizing the anomalous Hall effect [1]. The telegraph noise of Pt/Co/Pt dots (diameter <40nm, Co thickness <1nm) is measured in the superparamagnetic regime. The switching frequency is determined and analyzed with the Néel-Arrhenius law. We obtain attempt frequencies that deviate by orders of magnitude from the commonly assumed GHz range [2]. To investigate the influence of the energy barrier, the anisotropy has been measured for the initial film and dots as a function of temperature. A small variation of the uniaxial anisotropy constant KEff is found, which explains the deviations in the attempt frequencies. Funding by DFG via SFB 668 is gratefully acknowledged. [1] A. Neumann et al. Nano Letters 13, p2199-2203, (2014) [2] Bean and Livingston, J. Appl. Phys. 30, 120S, (1959)