Dresden 2017 – scientific programme

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MA: Fachverband Magnetismus

MA 35: Magnetic Particles / Clusters

MA 35.2: Talk

Wednesday, March 22, 2017, 09:45–10:00, HSZ 101

Determining anisotropy and magnetic moment of single nanodots from switching time measurements — •Stefan Freercks, Carsten Thönnißen, Eva-Sophie Wilhelm, Philipp Staeck, and Hans Peter Oepen — Institut für Nanostruktur- und Festkörperphysik, Universität Hamburg, Germany

We use the anomalous Hall-effect to investigate the magnetization reversal in single Pt/Co/Pt nanodots (diameter <40nm, Co thickness < 1nm) with perpendicular magnetization. The dots are fabricated by electron beam lithography and ion milling out of thin multilayers [1]. We have investigated the time dependent switching in the superparamagnetic regime and determine the temperature dependence of the switching frequency. The Néel-Arrhenius plot reveals attempt frequencies that deviate from the expected values in the GHz regime [2]. Measuring the occupation as a function of field along the easy axis gives access to the magnetic moment. In the blocked regime a magnetic field is applied perpendicular to the easy axis, which reduces the energy barrier and causes thermal switching. In accordance to experiments in the superparamagnetic regime the switching times are determined as a function of field strength. The field dependent switching times allow for the determination of the dot moment and total anisotropy as a function of temperature. Dots and film reveal a similar temperature behavior. 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)