Spin Splitting ofsandpStates in Single Atoms and Magnetic Coupling in Dimers on a Surface

Abstract

Electronic states of magnetic atoms (Mn, Fe, and Co) and artificially assembled dimers (${\mathrm{Mn}}_2$, ${\mathrm{Fe}}_2$, and ${\mathrm{Co}}_2$) on a NiAl(110) surface were probed by scanning tunneling spectroscopy at 17 K. Resonance peaks characteristic of each adsorbed species were observed in the unoccupied density of states. Comparison of the measured spectra with calculations by density functional theory revealed spin splitting in the unoccupied states with $s$ and $p$ characters for the single magnetic adatoms and addimers. The magnitude of the resonance splitting for the adatoms increased with the calculated values of magnetic moments. The resonance structures for the addimers exhibited signatures of their internal magnetic coupling.