We report on spin-resolved photoemission spectroscopy measurements at the interface between a 25-nm -thick Fe3O4(111) thin film and a 2-nm -thick gamma-Al2O3(111) layer. The Fe3O4 layer remains stoichiometric even after being covered by gamma-Al2O3 and exhibits a negative spin polarization of ˜-40% , after remanence correction. This value should be considered as a lower bound for the spin polarization and demonstrates that Fe3O4 remains a spin polarized material even after incorporation in a bilayer.