We report experimental evidence that hydrogen termination largely enhances the spin polarization of an ${\text{Fe}}_3{\text{O}}_4\left(100\right)$ surface. An in situ prepared ${\text{Fe}}_3{\text{O}}_4\left(100\right)/\text{MgO}\left(100\right)$ film surface was exposed to atomic hydrogen and its surface spin polarization $\left(P\right)$ was monitored with a spin-polarized metastable helium-atom beam under external magnetic fields of 0–5 T. The spin asymmetry at the high-energy cutoff, which reflects $P$ at the Fermi level of the topmost surface, increased from $<5\mathrm{\%}$ to $>50\mathrm{\%}$ at 298 K by H adsorption. The enhancement in $P$ was found to be consistent with the H-induced change in the surface electronic states predicted by a density-functional theory calculation.

• Received 2 November 2009

DOI:https://doi.org/10.1103/PhysRevB.81.193402