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Photoinduced effects on the magnetic properties of the (Fe <sub/>0.2</sub> Cr <sub/>0.8</sub> ) <sub/>1.5</sub> [Cr(CN) <sub/>6</sub> ] Prussian blue analogue.
摘要： One of the most attractive characteristics of some Prussian blue derivatives is the sensitivity of their magnetic properties to the irradiation with light. In this work photoinduced effects in the (Fe0.2Cr0.8)1.5 [Cr(CN)6]·15 H2O PBA have been studied by means of X ray-based spectroscopies and magnetometry. It is found that the photosensitivity of this compound is mostly centred on the Fe cations: the exposure to green light induces a transfer of electrons from them to the Cr that provokes a reversal of the previously existing linkage isomerization and increases the elastic strain caused by the mis?t of the unit cells of the Fe–NC–Cr and Cr–NC–Cr sublattices. The green light also quenches the magnetism of the FeII high-spin (HS) ions present in the sample and reduces the magnetic moments of most of the Cr cations except for CrII HS. Our study highlights the important role played by the mismatch between the unit cells of the coexisting sub-lattices in ternary Prussian blue analogues.
关键词： magnetometry,photoinduced effects,magnetic properties,elastic strain,X-ray spectroscopies,Prussian blue analogues,linkage isomerization
更新于2025-09-19 17:15:36
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The origin of low bandgap and ferroelectricity of a co-doped BaTiO <sub/>3</sub>
摘要： We recently demonstrated the lowest bandgap ferroelectric, for visible light absorption in BaTi1?x(Mn1/2Nb1/2)xO3, a promising candidate material optoelectronic devices. Using a combination of x-ray spectroscopies and density functional theory (DFT) calculations, we here elucidate this compound’s electronic structure and the modifications induced by Mn doping. In particular, we are able to rationalize how this compound retains its ferroelectricity even through a significant reduction of the optical gap upon Mn doping. The local electronic structure and atomic coordination are investigated using x-ray absorption at the Ti K, Mn K, and O K edges, which suggests only small distortions to the parent tetragonal ferroelectric system, BaTiO3, thereby providing a clue to the substantial retention of ferroelectricity in spite of doping. Features at the Ti K edge, which are sensitive to local symmetry and an indication of Ti off-centering within the Ti-O6 octahedra, show modest changes with doping and strongly corroborates our measured polarization values. Resonant photoelectron spectroscopy results suggest the origin of the reduction of the bandgap in terms of newly created Mn d bands that hybridize with O 2p states. X-ray absorption spectra at the O K edge provide evidence for new states below the conduction band of the parent compound, illustrating additional contributions facilitating bandgap reduction.
关键词： ferroelectricity,Mn doping,x-ray spectroscopies,bandgap,density functional theory,BaTiO3
更新于2025-09-10 09:29:36
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Interfacing a Potential Purely Organic Molecular Quantum Bit with a Real-Life Surface
摘要： By using a multidisciplinary and multi-technique approach, we have addressed the issue of attaching a molecular quantum bit to a real surface. First, we demonstrate that an organic derivative of the pyrene-Blatter radical is a potential molecular quantum bit. Our study of the interface of the pyrene-Blatter radical with a copper-based surface reveals that the spin of the interface layer is not cancelled by the interaction with the surface and that the Blatter-radical is resistant in presence of molecular water. Although the measured pyrene-Blatter derivative quantum coherence time is not the highest value known, this molecule is known as a “super stable” radical. Conversely, other potential qubits show poor thin film stability upon air exposure. Therefore, we discuss strategies to make molecular systems candidates as qubits competitive, bridging the gap between potential and real applications.
关键词： X-ray spectroscopies,quantum bits,organic radicals,spinterfaces,interfaces
更新于2025-09-09 09:28:46