Structural, magnetic and Magneto optical properties of $\mathrm{Fe_3O_4/NiO}$ bilayers on MgO(001)

Ultrathin magnetite ($Fe_{3}O_{4}$) films are attractive for applications in the field of spintronics due to their ferrimagnetic behavior with assumed high degree of spin polarized electrons at the Fermi energy. For these applications, it is necessary to form epitactical bilayer structure combining ferrimagnetic magnetite with an antiferromagnetic layer. Therefore, here we study $Fe_{3}O_{4}$/NiO bilayers on MgO(001) substrates. Bilayers grown by reactive molecular beam epitaxy are stoichiometric and have well-developed surface and interface structures. The NiO layers are laterally pinned to the structure of the MgO(001) substrate while the magnetite films gradually relax. The interfaces show smooth morphologies and the films have very homogeneous film thickness necessary for spintronical applications. The magnetic and magneto optical properties of the $Fe_{3}O_{4}$/NiO bilayers were probed by the magneto optical Kerr effect. Compared to single $Fe_{3}O_{4}$ layers on MgO(001), the bilayers show complicated ferrimagnetic behavior depending on the azimuthal direction of the external applied field. The coercive field of the bilayers, however, is increased with the coercive field of single layer $Fe_{3}O_{4}$/MgO(001) structures making the Fe3O4/NiO bilayers attractive for spintronic applications