In this project, we will investigate the ultrafast dynamics of spin-polarized carriers in heterostructures of the ferromagnetic oxide EuO on various (insulating and conducting, para-, ferro-, and antiferromagnetic) substrates, and the spin transport properties across their interfaces. In terms of both basic understanding and potential ultrafast spintronic applications, we will address critical questions, for instance about the influence of the band structure on the spin dynamics, the strength and lifetimes of spin currents, and the interaction of different magnetic states in such heterojunctions.
Epitaxial films of EuO grown by oxide molecular beam epitaxy (MBE) will be investigated with various timeresolved techniques available within the CRC/TRR. Most prominently, extreme ultraviolet (XUV)-based time and angle-resolved photoemission spectroscopy (trARPES) will be used to investigate the dynamics of magnetization-induced changes in band structure (semi-metal-insulator transition, exchange splitting) and the lifetime of excited spin-polarized carriers. In addition, excitation above and below the optical bandgap of the oxide film will be used to study the spin transport properties across the metal-oxide interface and its dependence on spin polarization and magnetic state. Complementary experiments using other techniques available within the CRC (X-ray magnetic circular dichroism, THz spectroscopy, magneto-optical methods) will be used to quantify the transient spin polarization and transport dynamics of both substrate and oxide film.