Structural and magnetic investigation of the interfaces of $\mathrm{F}{\mathrm{e}}_3{\mathrm{O}}_4/MgO(001)$ with and without NiO interlayer

Abstract

We present an investigation on the structural and magnetic properties of the interfaces of $\mathrm{F}{\mathrm{e}}_3{\mathrm{O}}_4/MgO(001)$ and $\mathrm{F}{\mathrm{e}}_3{\mathrm{O}}_4/NiO/MgO(001)$ 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 $\mathrm{F}{\mathrm{e}}_3{\mathrm{O}}_4/MgO(001)$, the magnetooptical depth profiles at the $\mathrm{F}{\mathrm{e}}_{\mathrm{oct}}^{2+}$ and the $\mathrm{F}{\mathrm{e}}_{\mathrm{oct}}^{3+}$ resonant energies follow exactly the structural profile, while the magnetooptical depth profile at the $\mathrm{F}{\mathrm{e}}_{\mathrm{tet}}^{3+}$ resonance is offset by $3.2\pm 1.3$Å from the interface, consistent with a B-site interface termination of $\mathrm{F}{\mathrm{e}}_3{\mathrm{O}}_4$ with fully intact magnetic order. In contrast, for $\mathrm{F}{\mathrm{e}}_3{\mathrm{O}}_4/NiO(001)$, the magnetooptical depth profiles at the $\mathrm{F}{\mathrm{e}}_{\mathrm{oct}}^{2+}$ and the $\mathrm{N}{\mathrm{i}}^{2+}$ resonances agree with the structural profile, but the interface positions of the magnetooptical depth profiles at the $\mathrm{F}{\mathrm{e}}_{\mathrm{oct}}^{3+}$ and the $\mathrm{F}{\mathrm{e}}_{\mathrm{tet}}^{3+}$ resonances are laterally shifted by $3.3\pm 1.4$Å and $2.7\pm 0.9$Å, respectively, not consistent with a magnetically ordered stoichiometric interface. This may be related to an intermixed $(\mathrm{Ni},\mathrm{Fe})\mathrm{O}$ layer at the interface. The magnetooptical depth profiles at the Ni $L_3$ edge reveal uncompensated magnetic moments throughout the NiO film.

9 pages, 7 figures

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