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MA: Fachverband Magnetismus

MA 28: Surface Magnetism I (jointly with O)

MA 28.8: Talk

Wednesday, March 9, 2016, 11:30–11:45, H31

High frequency magnetization dynamics of individual atomic-scale magnets — •Stefan Krause, Andreas Sonntag, Jan Hermenau, Johannes Friedlein, and Roland Wiesendanger — Department of Physics, University of Hamburg, Jungiusstr. 11, 20355 Hamburg, Germany

Nucleation, annihilation and domain wall propagation are the most fundamental microscopic processes of magnetization reversal. Understanding and controlling these mechanisms is crucial for the development of future high-speed spintronic applications. In previous spin-polarized scanning tunneling microscopy (SP-STM) studies it was shown that the thermally activated magnetization reversal of Fe/W(110) nanomagnets consisting of less than 100 atoms is realized by nucleation and propagation instead of a coherent rotation of all magnetic moments. [1]

Within the present study we use SP-STM to investigate the magnetic ground state dynamics of individual nanomagnets over a wide temperature (T=30..70 K) and switching rate (ν=100 mHz..10 MHz) regime, combining telegraphic noise analysis and pump-probe schemes. With increasing T a transition between two Arrhenius regimes is observed, resulting in switching rates that are by orders of magnitude lower than expected from an extrapolation from the low temperature regime. The experimental results will be presented and interpreted in terms of an analytical model that accounts for the interplay of T-dependent nucleation, annihilation and propagation rates.

[1] S. Krause et al., Phys. Rev. Lett. 103, 127202 (2009).