M. Bode,1 S. Heinze,1,2 A. Kubetzka,1 O. Pietzsch,1

X. Nie,2 S. Bluegel,2 and R. Wiesendanger1

1 Institute of Applied Physics, University of Hamburg, Jungiusstr. 11, 20355

Hamburg, Germany

2 Institut für Festkörperforschung, Forschungszentrum Jülich, 52425 Jülich,

Germany

Spin-polarized scanning tunneling microscopy/spectroscopy (SP-STM/STS) using magnetic probe tips has long been considered as a promising tool in order to study magnetic properties down to the atomic scale. In the past we have focused our effort on the Gd(0001) surface which exhibits an exchange-split surface state [1] and can therefore be regarded as a model system for SP-STS. We showed that SP-STS allows the separation and correlation of topographic, electronic and magnetic properties within a single measurement [2].

Recently, we have performed experiments on self-organized Fe-nanowires and antiferromagnetic Mn films. The thickness of the nanowires amounts to two atomic layers only. Based on a detailed investigation of the spin-resolved electronic structure we could clearly observe the magnetic domain structure of the nanowires. It is governed by a dipolar antiferromagnetic coupling of adjacent wires which is mediated by the stray field. Our images allow the evaluation of the influence of structural defects such as, e.g., non-uniform width and separation of the wires.

As early as 1988 the 2D antiferromagnetic structure of a monolayer Mn film onnon-magnetic substrates has been theoretically proposed [3]. Only now we could proof this proposal by atomic-resolution SP-STM. The SP-STM experiments are explained on the basis of ab-initio electronic structure calculations using the full-potential linearized augmented plane wave (FLAPW) method.

[1] M. Bode et al.,Phys. Rev. Lett. 83, 3017 (1999).

[2] M. Bode, M. Getzlaff, and R. Wiesendanger ,Phys. Rev. Lett. 81, 4256 (1998).

[3] S. Bluegel, M. Weinert, and P.H. Dederichs, Phys. Rev. Lett. 60, 1077 (1988).