Negative spin polarization of theFe3O4∕γ−Al2O3interface measured by spin-resolved photoemission

Abstract

We report on spin-resolved photoemission spectroscopy measurements at the interface between a $25\text{\ensuremath{-}}\mathrm{nm}$-thick ${\mathrm{Fe}}_{3}{\mathrm{O}}_{4}\phantom{\rule{0.3em}{0ex}}(111)$ thin film and a $2\text{\ensuremath{-}}\mathrm{nm}$-thick $\ensuremath{\gamma}\text{\ensuremath{-}}{\mathrm{Al}}_{2}{\mathrm{O}}_{3}\phantom{\rule{0.3em}{0ex}}(111)$ layer. The ${\mathrm{Fe}}_{3}{\mathrm{O}}_{4}$ layer remains stoichiometric even after being covered by $\ensuremath{\gamma}\text{\ensuremath{-}}{\mathrm{Al}}_{2}{\mathrm{O}}_{3}$ and exhibits a negative spin polarization of $\ensuremath{\sim}\ensuremath{-}40%$, after remanence correction. This value should be considered as a lower bound for the spin polarization and demonstrates that ${\mathrm{Fe}}_{3}{\mathrm{O}}_{4}$ remains a spin polarized material even after incorporation in a bilayer.