Spin-polarized tunneling effects observed on the oxygen-terminated Fe3O4 (111) surface

Under oxidizing preparation conditions the magnetite (111) surface reconstructs to a highly ordered superlattice. This surface reconstruction represents an oxygen termination of the magnetite bulk. We employ spin-polarized (SP) scanning tunneling magnetization (STM) to study the spin-dependent tunneling between a magnetite (111) sample and an antiferromagnetic tip through a vacuum barrier. Atomic scale STM images show significant magnetic contrast corresponding to variations in the local surface states induced by oxygen vacancies. The local variations of the tunneling magnetoresistance around these vacancies correspond to 150%. By employing SP–STM measurements and first principles calculations we could conclude that an oxygen top layer considerably changes the SP properties of the magnetite surface.