Optical effects in spin-polarized scanning tunneling microscopy with GaAs probes

Experiments on spin-polarized tunneling with GaAs probes were performed in a scanning tunneling microscope. The central issue is the detection of a sp in-dependent contribution to the tunnel current between a ferromagnetic sam ple and a GaAs probe tip, in which a spin polarization is optically induced . Measurements in ultrahigh vacuum on Co surfaces show a marked dependence on applied voltage and lateral variations on the scale of the magnetic doma in size, as expected for spin-polarized tunneling. However, using Au test s amples it is shown that purely optical effects complicate the data interpre tation, and prevent an unambiguous demonstration of spin sensitivity with t his method in its present form. (C) 1999 Published by Elsevier Science B.V. All rights reserved.