Investigation of the spin crossover behaviour of a sublimable Fe(II)-qsal complex: from the bulk to a submonolayer on graphene/SiO.

We synthesized a sublimable molecular spin crossover Fe(II) complex based on the Schiff base tridentate ligand qsal-NEt (5-diethylamino-2-((quinolin-8-ylimino)methyl)phenol). The compound undergoes a transition in temperature with thermally induced excited spin state-trapping (TIESST) for high-temperature sweep rates, which can be suppressed by reducing the sweep rate. The X-ray absorption spectroscopy (XAS) studies on the microcrystalline powder confirm the TIESST effect.

Assembling Fe single-molecule magnets on a TiO monolayer.

The decoration of technologically relevant surfaces, such as metal oxides, with Single-Molecule Magnets (SMMs) constitutes a persistent challenge for the integration of these molecular systems into novel technologies and, in particular, for the development of spintronic and quantum devices. We used UHV thermal sublimation to deposit tetrairon(III) propeller-shaped SMMs (Fe) as a single layer on a TiO ultrathin film grown on Cu(001). The properties of the molecular deposit were studied using a multi-technique approach based on standard topographic and spectroscopic measurements, which demonstrated that molecules remain largely intact upon deposition.

Finite size effects on the metamagnetic phase transition in a thick B2 FeRh nanocluster film.

FeRh alloys in the CsCl-type (B2) chemically ordered phase present an antiferromagnetic to ferromagnetic order transition around 370 K observed in bulk and continuous films but absent in nanoclusters. In this study, we investigate the thermal magnetic behavior of a thick film composed of assembled FeRh nanoclusters preformed in the gas phase. This work reveals a broad and asymmetric metamagnetic transition with a consequent residual magnetization at low temperature.

Temperature Induced Reversible Switching of the Magnetic Anisotropy in a Neodymium Complex Adsorbed on Graphite.

Controlling the magnetic anisotropy of molecular layers assembled on a surface is one of the challenges that needs to be addressed to create the next-generation spintronic devices. Recently, metal complexes that show a reversible solid-state switch of their magnetic anisotropy in response to physical stimuli, such as temperature and magnetic field, have been discovered. The complex Nd(trensal) (Htrensal = 2,2',2''-tris(salicylideneimino)triethylamine) is predicted to exhibit such property.

Orbital Magnetic Moment and Single-Ion Magnetic Anisotropy of the = 1/2 K[Fe(CN)] Compound: A Case Where the Orbital Magnetic Moment Dominates the Spin Magnetic Moment.

The potassium hexacyanoferrate(III), K[Fe(CN)], is known for its exceptional magnetic anisotropy among the 3d transition metal series. The Fe(III) ions are in the = 1/2 low spin state imposed by the strong crystal field of the cyanido ligands. A large orbital magnetic moment is expected from previous publications.

Hybrid Heterostructures of a Spin Crossover Coordination Polymer on MoS : Elucidating the Role of the 2D Substrate.

Controlling the deposition of spin-crossover (SCO) materials constitutes a crucial step for the integration of these bistable molecular systems in electronic devices. Moreover, the influence of functional surfaces, such as 2D materials, can be determinant on the properties of the deposited SCO film. In this work, ultrathin films of the SCO Hofmann-type coordination polymer [Fe(py) {Pt(CN) }] (py = pyridine) onto monolayers of 1T and 2H MoS polytypes are grown.

Interface versus Bulk Light-Induced Switching in Spin-Crossover Molecular Ultrathin Films Adsorbed on a Metallic Surface.

Spin-crossover molecules present the unique property of having two spin states that can be controlled by light excitation at low temperature. Here, we report on the photoexcitation of [Fe((3, 5-(CH)Pz)BH)] (Pz = pyrazolyl) ultrathin films, with thicknesses ranging from 0.9 to 5.

Magnetic molecules as local sensors of topological hysteresis of superconductors.

Superconductors and magnetic materials, including molecules, are key ingredients for quantum computing and spintronics. However, only a little is known about how these materials interact in multilayer nanostructures like the hybrid architectures nowadays under development for such advanced applications. Here, we show that a single layer of magnetic molecules, Terbium(III) bis-phthalocyaninato (TbPc) complexes, deposited under controlled UHV conditions on a superconducting Pb(111) surface is sensitive to the topology of the intermediate state of the superconductor, namely to the presence and evolution of superconducting and normal domains due to screening and penetration of an external magnetic field.

Magnetic Ordering in Ultrasmall Potassium Ferrite Nanoparticles Grown on Graphene Nanoflakes.

Magnetic nanoparticles are central to the development of efficient hyperthermia treatments, magnetic drug carriers, and multimodal contrast agents. While the magnetic properties of small crystalline iron oxide nanoparticles are well understood, the superparamagnetic size limit constitutes a significant barrier for further size reduction. Iron (oxy)hydroxide phases, albeit very common in the natural world, are far less studied, generally due to their poor crystallinity.

Magnetic Hysteresis in a Monolayer of Oriented 6 nm CsNiCr Prussian Blue Analogue Nanocrystals.

Prussian blue analogue nanocrystals of the CsNi[Cr(CN)] cubic network with 6 nm size were assembled as a single monolayer on highly organized pyrolytic graphite (HOPG). X-ray magnetic circular dichroism (XMCD) studies, at the Ni and Cr L edges, reveal the presence of an easy plane of magnetization evidenced by an opening of the magnetic hysteresis loop (coercive field of ≈200 Oe) when the magnetic field, , is at 60° relative to the normal to the substrate. The angular dependence of the X-ray natural linear dichroism (XNLD) reveals both an orientation of the nanocrystals on the substrate and an anisotropy of the electronic cloud of the Ni and Cr coordination sphere species belonging to the nanocrystals' surface.

Thermal Bistability of an Ultrathin Film of Iron(II) Spin-Crossover Molecules Directly Adsorbed on a Metal Surface.

Spin-crossover molecules are very attractive compounds to realize multifunctional spintronic devices. Understanding their properties when deposited on metals is therefore crucial for their future rational implementation as ultrathin films in such devices. Using X-ray absorption spectroscopy, we study the thermal transition of the spin-crossover compound Fe((3,5-(CH)Pz)BH) from submonolayer to multilayers on a Cu(111) substrate.

Anomalous Light-Induced Spin-State Switching for Iron(II) Spin-Crossover Molecules in Direct Contact with Metal Surfaces.

Light-induced spin-state switching is one of the most attractive properties of spin-crossover materials. In bulk, low-spin (LS) to high-spin (HS) conversion via the light-induced excited spin-state trapping (LIESST) effect may be achieved with a visible light, while the HS-to-LS one (reverse-LIESST) requires an excitation in the near-infrared range. Now, it is shown that those phenomena are strongly modified at the interface with a metal.

Reversible coordination-induced spin-state switching in complexes on metal surfaces.

Molecular spin switches are attractive candidates for controlling the spin polarization developing at the interface between molecules and magnetic metal surfaces, which is relevant for molecular spintronics devices. However, so far, intrinsic spin switches such as spin-crossover complexes have suffered from fragmentation or loss of functionality following adsorption on metal surfaces, with rare exceptions. Robust metal-organic platforms, on the other hand, rely on external axial ligands to induce spin switching.

Iron Phthalocyanine and Ferromagnetic Thin Films: Magnetic Behavior of Single and Double Interfaces.

Metal-phthalocyanines are quasi-planar heterocyclic macrocycle molecules with a highly conjugated structure. They can be engineered at the molecular scale (central atom, ligand) to tailor new properties for organic spintronics devices. In this study, we evaluated the magnetic behavior of FePc in a ∼1 nm molecular film sandwiched between two ferromagnetic films: cobalt (bottom) and nickel (top).

Correction: Effect of nanostructuration on the spin crossover transition in crystalline ultrathin films.

[This corrects the article DOI: 10.1039/C8SC04935A.].

Effect of nanostructuration on the spin crossover transition in crystalline ultrathin films.

Mastering the nanostructuration of molecular materials onto solid surfaces and understanding how this process affects their properties are of utmost importance for their integration into solid-state electronic devices. This is even more important for spin crossover (SCO) systems, in which the spin transition is extremely sensitive to size reduction effects. These bi-stable materials have great potential for the development of nanotechnological applications provided their intrinsic properties can be successfully implemented in nanometric films, amenable to the fabrication of functional nanodevices.

Atomic Scale Evidence of the Switching Mechanism in a Photomagnetic CoFe Dinuclear Prussian Blue Analogue.

Molecular complexes based on Prussian Blue analogues have recently attracted considerable interest for their unique bistable properties combined to ultimately reduced dimensions. Here, we investigate the first dinuclear FeCo complex exhibiting both thermal and photomagnetic bistability in the solid state. Through an experimental and theoretical approach combining local techniques-X-ray absorption spectroscopy (XAS), X-ray magnetic circular dichroism (XMCD), and ligand field multiplet calculations-we were able to evidence the changes occurring at the atomic scale in the electronic and magnetic properties.

Tunable Spin-Superconductor Coupling of Spin 1/2 Vanadyl Phthalocyanine Molecules.

Atomic-scale magnetic moments in contact with superconductors host rich physics based on the emergence of Yu-Shiba-Rusinov (YSR) magnetic bound states within the superconducting condensate. Here, we focus on a magnetic bound state induced into Pb nanoislands by individual vanadyl phthalocyanine (VOPc) molecules deposited on the Pb surface. The VOPc molecule is characterized by a spin magnitude of 1/2 arising from a well-isolated singly occupied d -orbital and is a promising candidate for a molecular spin qubit with long coherence times.

Linking Electronic Transport through a Spin Crossover Thin Film to the Molecular Spin State Using X-ray Absorption Spectroscopy Operando Techniques.

One promising route toward encoding information is to utilize the two stable electronic states of a spin crossover molecule. Although this property is clearly manifested in transport across single molecule junctions, evidence linking charge transport across a solid-state device to the molecular film's spin state has thus far remained indirect. To establish this link, we deploy materials-centric and device-centric operando experiments involving X-ray absorption spectroscopy.

Weak Ferromagnetic Interaction at the Surface of the Ferrimagnetic RbCo[Fe(CN)]·11HO Photoexcited State.

CoFe Prussian blue analogues (PBAs) are well-known for their magnetic bistability tuned by external stimuli. The photoswitching properties are due to the electron transfer from Co-NC-Fe to Co-NC-Fe linkage, accompanied by the spin change of the Co ions (HS stands for high spin and LS for low spin). In this work, we investigated 100 nm particles of the RbCo[Fe(CN)]·11HO PBA (named RbCoFe).

Self-Assembly of TbPc Single-Molecule Magnets on Surface through Multiple Hydrogen Bonding.

The complexation between 2-ureido-4[1H]-pyrimidinone (UPy) and 2,7-diamido-1,8-naphthyridine (NaPy) is used to promote the mild chemisorption of a UPy-functionalized terbium(III) double decker system on a silicon surface. The adopted strategy allows the single-molecule magnet behavior of the system to be maintained unaltered on the surface.

Iron L-Edge X-ray Absorption and X-ray Magnetic Circular Dichroism Studies of Molecular Iron Complexes with Relevance to the FeMoco and FeVco Active Sites of Nitrogenase.

Herein, a systematic study of a series of molecular iron model complexes has been carried out using Fe L-edge X-ray absorption (XAS) and X-ray magnetic circular dichroism (XMCD) spectroscopies. This series spans iron complexes of increasing complexity, starting from ferric and ferrous tetrachlorides ([FeCl]), to ferric and ferrous tetrathiolates ([Fe(SR)]), to diferric and mixed-valent iron-sulfur complexes [FeSR]. This test set of compounds is used to evaluate the sensitivity of both Fe L-edge XAS and XMCD spectroscopy to oxidation state and ligation changes.