EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

Iron/Non-Magnetic (NM) metallic bilayers with a variety of cupping layers as spin detectors have been a topic of extensive studies in the last years in the field of spintronics. In the specific project we study the effect of a very thin overlayer for spin transport phenomena. Except of their main role, the NM layers protects the magnetic film in order to remain chemically pure and structurally stable. Epitaxial growth proved that enhances spin pumping and magnetic proximity effects. We used molecular beam epitaxy for the material deposition on MgO(100) substrates and we developed Fe(12nm)/Pt(3nm), Fe(12nm)/Au(3nm) and Fe(12nm)/Pd(3nm) bilayers, under the substrate temperature of 300 degrees Celsius. The structural characterization was performed via Χ-Ray diffraction (XRD), confirming the epitaxial growth in all of the cases, and deduced the presence of elastic strain from the peak analysis, as a function of the planar mismatch between the materials. Supporting X-ray photoelectron spectroscopy (XPS) was applied, analyzing the chemical state of each layer in different depths from the surface, during an Ar+ ion etching process. The combined analysis revealed that the Au overlayer caused short range interdiffusion between the meals, Pd cupping layer was not able to fully protect the ferromagnetic layer from oxidation at the studied thickness, while Pt prevented sufficiently the above phenomena. The findings compared with the in-plane and out-of-plane static magnetic properties investigated by SQUID magnetic loops, determined the origin of the decreased coercive field and saturation magnetization of the Fe/Pd systems and the enhancement of the magnetic strength for the Fe/Au and Fe/Pt bilayers. Even more, ferromagnetic resonance (FMR) experiments provided an increased Gilbert spin dumping parameter for the Fe/Pt and Fe/Au films and an insufficient parameter for the Fe/Pd systems.