Electronic and magnetic properties of bulk Cr tips for scanning tunneling spectroscopy

The electronic and magnetic properties of bulk Cr tips for scanning tunneling microscopy have been investigated by means of density functional theory (DFT) calculations and scanning tunneling spectroscopy (STS) measurements. Spin-resolved densities of states (DOS) were calculated for model tips, i.e., Cr adatoms and clusters on ideal Cr surfaces. STS measurements on Au(111) and Si(111)-7x7 have been interpreted by modeling the tunneling process in a Wentzel-Kramers-Brillouin approximation in order to ascertain the role of tip DOS features. Calculated spin-resolved electronic properties of Cr tips have been used to revisit spin-polarized (SP) STS measurements from the literature. The agreement between experimental findings and DFT calculations confirms the relevance of the knowledge of tip electronic properties and of an appropriate model for the tunneling process in the interpretation of STS and SP-STS data.