The inorganic/molecular spinterface is an ideal platform for generating extraordinary spin effects. Understanding and controlling these spin-related effects is mandatory for the exploitation of such interfaces in devices. For this purpose we have investigated the adsorption of α-sexithiophene (α-6T) on La 0.7 Sr 0.3 MnO 3 (LSMO) as one of the prototypical material combinations used in organic spintronic devices. Atomic force microscopy (AFM), confocal photoluminescence, X-ray and utraviolet photoelectron spectroscopy, and metastable de-excitation spectroscopy unraveled the structure and the electronic configuration of 6T for various surface coverages. This data set allowed the determination of the characteristic features of occupied states: the band diagram and the work function. Finally, density functional theory enabled us to establish that the spin polarization in 6T molecular orbitals critically depends on the termination layer of LSMO, showing a substantial effect on the MnO-terminated one only. We believe that this research provides important hints for a comprehensive understanding of spinterface effects in general and offers key suggestions for the optimization of 6T/LSMO-based spin devices through the engineering of LSMO termination layer.
In this work, a simple method to follow the evolution of the surface of thin films during growth on substrates characterised by high roughness is detailed. To account for real cases as much as possible, the approach presented is based on the hypothesis that deposition takes place under nonstochastic conditions, such as those typical of many thin film processes in industry and technology. In this context, previous models for roughness replication, which are mainly based on idealised deposition conditions, cannot be applied and thus ad hoc approaches are required for achieving quantitative predictions. Here it is suggested that under nonstochastic conditions a phenomenological relation can be proposed, mainly based on local roughening of surface, to monitor the statistical similarity between the film and the substrate during growth or, in other words, to detect changes of the bare substrate morphological profile occurring during the film growth on top. Such approximation is based on surface representation in terms of power spectral density of surface heights, derived from topographic images; in this work, such method will be tested on two separate batches of synthetic images which simulate thin films growth onto a real rough substrate. In particular, two growth models will be implemented: the first reproduces the surface profile obtained during an atomic force microscopy measurement by using a simple geometrical envelope of surface, regardless the thin film growth mechanism; the second reproduces the columnar growth expected under nonstochastic deposition conditions. It will be shown that the approach introduced is capable to highlight differences between the two batches and, in the second case, to quantitatively account for the replication of the substrate roughness during growth. The
The hybridization of the surface orbitals of thin ferromagnetic layers with molecular orbitals represents a soft but efficient technology that is able to induce in ferromagnetic component radical modifications of the key magnetic parameters, such as magnetization, magnetic anisotropy, and others. These effects are investigated in 7 nm thick polycrystalline Co films interfaced with C60 and Gaq3 molecular layers by combining 59Co Ferromagnetic nuclear resonance spectroscopy (FNR) and magneto‐optic kerr effect (MOKE) techniques. It is demonstrated that the surface hybridization produces a significant magnetic hardening with respect to a reference Co/Al system and that the molecule‐induced effects modify the magnetic properties of entire Co layer, propagating for several nm from the interface. The FNR spectroscopy also reveals a reconstruction of the magnetic environment at the cobalt surface, whose observation in polycrystalline films is especially intriguing. The results shed new and unexpected light on the interfacial physics in such systems, whose understanding necessitates further experimental and theoretical research.
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