Dresden 2011 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 62: Magnetic Imaging

MA 62.1: Vortrag

Freitag, 18. März 2011, 10:45–11:00, HSZ 04

Observation of superparamagnetism in image potential states using SP-STM — •Anika Schlenhoff, Andreas Sonntag, Stefan Krause, and Roland Wiesendanger — Institute of Applied Physics, University of Hamburg

Several eV above their Fermi energy ferromagnets exhibit image potential states (IPS) which are located nanometers above the surface in the vacuum. As these states are spin-split, their magnetization can be imaged by spin-polarized scanning tunneling microscopy (SP-STM) [1]. Due to the great tip-sample distance, the risk for destructive mechanical contact is minimized. Whereas magnetic IPS have been extensively studied by laterally averaging methods [2], only recently first SP-STM experiments on IPS were performed on bulk-like Fe/W(110) [1]. It is an open question wether magnetic IPS are also observable above atomic-scale, only one atomic layer high magnets. Therefore, we investigate IPS above Fe/W(110) monolayer islands consisting only of about 100 atoms. These nanoislands exhibit a monodomain magnetization state and thermally switch their magnetization at 40 K [3]. In our SP-STM experiments, this switching behavior is recorded within the IPS, thereby demonstrating that the exchange splitting of IPS is observable even above atomic-scale magnetic nanostructures. Influences of the increased bias voltage on the thermal switching behavior will be discussed.

[1] A. Kubetzka et al., Appl. Phys. Lett. 91, 012508 (2007).

[2] M. Donath et al., Surf. Sci. 601, 5701 (2007).

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