Speaker
Description
The spin-dependent electronic structure of buried oxide–ferromagnet interfaces governs the performance of magnetic tunnel junctions,[1,2] but remains difficult to access directly with conventional surface-sensitive spectroscopies. Here, we show that spin-resolved momentum microscopy, i.e. spin-resolved ARPES in full-field momentum-imaging mode, can probe the buried MgO/Fe(100) interface and reveal how atomic-scale oxygen control modifies spin-selective tunneling states.[3]
Using reactive MgO growth on Fe(100), we tune the interface from an oxygen-free termination to a fully oxygen-intercalated layer while preserving epitaxial order. Despite the insulating MgO overlayer, momentum-resolved photoemission detects pronounced interface-derived fingerprints in k-space that persist up to MgO thicknesses of 8 monolayers. These fingerprints provide a direct spectroscopic readout of the buried interface chemistry and allow us to distinguish oxygen-free, partially oxidized, and oxygen-intercalated terminations.
Most importantly, spin-resolved Fermi-surface maps reveal a strong dependence of the interfacial spin texture on oxygen incorporation. Spin-resolved Fermi-surface maps show that oxygen-free MgO/Fe interfaces strongly suppress minority-spin spectral weight at the Fermi energy, consistent with coherent spin filtering through crystalline MgO. In contrast, oxygen intercalation restores minority-spin intensity and reduces the spin contrast at the Fermi level. These results demonstrate that spin-resolved ARPES can directly access buried spintronic interfaces and visualize the electronic states underlying spin-selective tunneling. More broadly, they establish interfacial oxygen as a measurable and tunable parameter for engineering oxide–ferromagnet junctions.
[1] W. H. Butler et al., Phys. Rev. B 63, 054416 (2001).
[2] S. S. P. Parkin et al., Nat. Mater. 3, 862–867 (2004).
[3] D. M. Janas et al., Advanced Science, 2026, e23165.