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

TL;DR

This study investigates the structural and magnetic properties of Fe3O4/MgO(001) and Fe3O4/NiO/MgO(001) interfaces using advanced x-ray techniques, revealing differences in interface termination and magnetic order with and without NiO interlayer.

Contribution

It provides detailed cation-specific magnetic depth profiles at the interfaces, highlighting the effects of NiO interlayer on magnetic and structural interface properties.

Findings

Fe3O4/MgO(001) has a B-site interface termination with magnetic order intact.

NiO interlayer causes lateral shifts in magnetic interface positions.

Uncompensated magnetic moments are present throughout the NiO film.

Abstract

We present an investigation on the structural and magnetic properties of the interfaces of $\mathrm{Fe_3O_4/MgO(001)}$ and $\mathrm{Fe_3O_4/NiO/MgO(001)}$ 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 $\mathrm{Fe_3O_4/MgO(001)}$, the magnetooptical depth profiles at the $\mathrm{Fe^{2+}_{oct}}$ and the $\mathrm{Fe^{3+}_{oct}}$ resonant energies follow exactly the structural profile, while the magnetooptical depth profile at the $\mathrm{Fe^{3+}_{tet}}$ resonance is offset by $3.2\pm1.3\,$\r{A} from the interface, consistent with a B-site interface termination of $\mathrm{Fe_3O_4}$ with fully intact magnetic order. In contrast, for $\mathrm{Fe_3O_4/NiO(001)}$, the magnetooptical depth profiles at the $\mathrm{Fe^{2+}_{oct}}$ and the $\mathrm{Ni^{2+}}$ resonances agree with the structural profile, but the interface positions of the magnetooptical depth profiles at the $\mathrm{Fe^{3+}_{oct}}$ and the $\mathrm{Fe^{3+}_{tet}}$ resonances are laterally shifted by $3.3\pm 1.4\,$\r{A} and $2.7\pm0.9\,$\r{A}, respectively, not consistent with a magnetically ordered stoichiometric interface. This may be related to an intermixed $\mathrm{(Ni,Fe)O}$ layer at the interface. The magnetooptical depth profiles at the Ni $L_3$ edge reveal uncompensated magnetic moments throughout the NiO film.