Structural and magnetic investigation of the interfaces of $\mathrm{Fe_3O_4/MgO(001)}$ with and without NiO interlayer

Abstract

We present an investigation on the structural and magnetic properties of the interfaces of Fe3O4/MgO(001) and Fe3O4/NiO/MgO(001) by extracting cation-selective magnetooptical depth profiles by means of x-ray magnetic reflectivity (XRMR) in combination with charge-transfer multiplet simulations of x-ray magnetic circular dichroism (XMCD) data. For Fe3O4/MgO(001), the magnetooptical depth profiles at the Fe 2+ oct and the Fe 3+ oct resonant energies follow exactly the structural profile, while the magnetooptical depth profile at the Fe 3+ tet resonance is offset by 3.2 ± 1.3 Å from the interface, consistent with a B-site interface termination of Fe3O4 with fully intact magnetic order. In contrast, for Fe3O4/NiO(001), the magnetooptical depth profiles at the Fe 2+ oct and the Ni 2+ resonances agree with the structural profile, but the interface positions of the magnetooptical depth profiles at the Fe 3+ oct and the Fe 3+ tet resonances are laterally shifted by 3.3 ± 1.4 Å and 2.7 ± 0.9 Å, respectively, not consistent with a magnetically ordered stoichiometric interface. This may be related to an intermixed (Ni, Fe)O layer at the interface. The magnetooptical depth profiles at the Ni L3 edge reveal uncompensated magnetic moments throughout the NiO film.