Scanning tunneling microscopy detection of spin polarized resonant surface bands: The example of Fe(001)

We study theoretically the effect of a spin polarized resonant surface band on the conductance of scanning tunneling spectroscope with a spin polarized tip (SP-STM). Using the example of the Fe(001) surface, we show that a minority-spin surface state can induce a bias dependence of the tunneling differential conductance which depends strongly on the orientation of the magnetization in the SP-STM tip relative to the magnetization axis in the surface. We propose the use of this effect to determine the spin character of the surface band.