Regensburg 2010 – scientific programme

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MA: Fachverband Magnetismus

MA 25: Surface Magnetism / Magnetic Imaging I

MA 25.5: Talk

Thursday, March 25, 2010, 11:15–11:30, H23

Cr Bulk Tips for Spin Polarized Scanning Tunneling Microscopy with both In-plane and Out-of-plane Sensitivity — •Anika Emmenegger, Gabriela Herzog, Stefan Krause, and Roland Wiesendanger — Institute of Applied Physics, University of Hamburg

Spin-polarized scanning tunneling microscopy (SP-STM) is a powerful technique to investigate magnetic surface properties on the local scale. The advantage of antiferromagnetic probe tips, e.g. Cr- or Mn-coated W-tips, is their negligible stray field, that otherwise may interact with the sample magnetization. Chromium has a bulk Néel temperature of 311 K which makes it a promising bulk tip material for SP-STM measurements over a wide temperature range.

While first indications exist that Cr bulk tips are sensitive to the in-plane-component of sample magnetization [1], we show that these tips are also sensitive to the out-of-plane component. After introducing our ex situ and in situ tip preparation method we present SP-STM measurements on 1.8 monolayers of Fe/W(110) which is known to have the easy magnetization direction in the surface plane for the monolayer [2] and perpendicular to the surface in the second layer [3]. Imaging with a Chromium bulk tip reveals a magnetic contrast in the monolayer as well as in the double layer, thereby proving not only the in-plane but also the out-of-plane sensitivity of the tip.

[1] A. L. Bassi et al., APL 91, 173120 (2007).

[2] M. Pratzer et al., PRL 87, 127201 (2001).

[3] O. Pietzsch et al., PRL 84, 5212 (2000).