Effect of dichroism in the GaAs-tip-based spin polarized STM

In this paper, we investigate the origin of spurious signals in the GaAs-tip-based spin-polarized scanning tunneling microscope setup. Experimentally as well as theoretically, dichroism and birefringence are found to induce a power modulation signal up to a 10% depth. In particular, the presence of dichroism fluctuations in the sample’s substrate, at a submicronic scale and of non-magnetic origin, led to the formation of an image showing a domain-like structure on a micarAu 10 nm.non-magnetic sample. As a conclusion, this parasitic signal is therefore competing with the expected spin-dependent tunneling conductance phenomenon. Finally, we discuss of a new image obtained with a high-quality, microfabricated tips, where both phenomena may be present at the same time. q1999 Elsevier Science B.V. All rights reserved.