Towards Spin-Polarized Scanning Tunneling Microscopy on Magnetite (110)

We study the structure and the magnetic properties of the (110) surfaces of magnetite Fe3O4 thin films by scanning tunneling microscopy (STM) and spectroscopy (STS). The STM images Show a surface reconstruction consisting of ridges along the [(1) over bar 10] direction. The data indicate a pure outermost layer followed underneath by a Mg2+-contaminated layer. The metallic and semiconductor-like shapes of the measured current-voltage (1-V) curves indicate different thicknesses of the contaminated layer. While the W tips show in the current map small differences between the lops and valleys of ridges, the antiferromagnetic MnNi tips show a strong contrast at 0.3 and -0.7 V bias voltages. We discuss whether these observations can be related to the detection of spin-polarized current.