Dresden 2020 – scientific programme

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DS: Fachverband Dünne Schichten

DS 36: Thin Oxides and Oxide Layers I (joint session DS/HL/O)

DS 36.5: Talk

Thursday, March 19, 2020, 10:30–10:45, CHE 91

Thermal phase transformations through iron oxides/ oxide substrates interfaces — •Mai Hussein Hamed^1,2, David N. Mueller¹, Tomáš Duchoň¹, Ronja Hinz¹, Claus M. Schneider^1,3, and Martina Müller^1,4 — ¹Peter-Grünberg-Institut (PGI-6), Forschungszentrum Jülich GmbH, Germany — ²Faculty of Science, Helwan University, Cairo, Egypt — ³Fakultät für Physik, Duisburg-Essen Universität , Germany — ⁴Experimentelle Physik I, Technische Universität Dortmund, Germany

Oxide heterostructures possess a wide range of electrical and magnetic properties arising, in particular, vie interactions across their interfaces. Therefore, our primary goal is understanding, controlling and tuning the interface properties. In this study, using hard X-ray photoelectron spectroscopy (HAXPES), we demonstrate phase transformations from Fe₃O₄ to either γ-Fe₂O₃ or FeO through active redox reactions across three relevant interfaces, i.e. (1) the outside atmosphere/Fe_xO_y film interface, (2) the interface between phase-transformed Fe_xO_y/Fe_xO_y intralayers and (3) the Fe_xO_y/oxide substrate interface. We find that the "active" oxide substrates (SrTiO₃ or YSZ) play an important role as an additional oxygen supplier or scavenger. This leads to a clear alteration of the standard temperature-pressure phase diagram of iron oxides. Accordingly, we calculate the effective oxygen pressure through the interfaces and adjust the phase diagram. Our findings allow us not only to control the interfaces but more importantly, to tune their physical functionalities by a controlled thermal phase design, giving access to far from equilibrium phases.