Electronic devices that use the spin degree of freedom hold unique prospects for future technology. The performance of these 'spintronic' devices relies heavily on the efficient transfer of spin polarization across different layers and interfaces. This complex transfer process depends on individual material properties and also, most importantly, on the structural and electronic properties of the interfaces between the different materials and defects that are common to real devices. Knowledge of these factors is especially important for the relatively new field of organic spintronics, where there is a severe lack of suitable experimental techniques that can yield depth-resolved information about the spin polarization of charge carriers within buried layers of real devices. Here, we present a new depth-resolved technique for measuring the spin polarization of current-injected electrons in an organic spin valve and find the temperature dependence of the measured spin diffusion length is correlated with the device magnetoresistance.R ecently great efforts have been undertaken to use the spin degree of freedom in electronic devices. These activities are fuelled by the potential prospects of spin-electronic (or 'spintronic') devices for example in terms of increased processing speed and integration, non-volatility, reduced power consumption, multifunctionality and their suitability for quantum computing 1 . The most common method for using the spin in devices is based on the alignment of the electron spin ('up' or 'down') relative to either a reference magnetic field or the magnetization orientation of a ferromagnetic layer. Device operation normally proceeds with measuring a quantity such as the electrical current that depends on how the degree of spin alignment is transferred across the device. The so-called 'spin valve' is a prominent example of such a spin-enabled device that has already revolutionized hard-drive read heads and magnetic memory 1 . The efficient transfer of spin polarization in real device structures remains one of the most difficult challenges in spintronics, because it is dependent on more than just the properties of the individual materials that comprise the device.Recently 2,3 , the use of organic materials in spintronics has become of significant interest, primarily owing to their ease and small cost of processing and electronic and structural flexibility. Furthermore, the extremely long spin coherence times found in organic materials offer considerable advantages over other materials 3 . This favourable property is related to two factors, first the weak spin-orbit coupling of light elements such as carbon and second to the small nuclear hyperfine interaction 4,5 . The latter arises because the electron transport in π-conjugated molecules is normally confined to molecular states, delocalized to the carbon rings, the predominant isotope of which, 12 C, has zero nuclear spin 4 .A common way to measure spin diffusion is based on time-resolved optical techniques, where spin-polarized charge carrie...

Fast-ion conductors are critical to the development of solid-state batteries. The effects of mechanochemical synthesis that lead to increased ionic conductivity in an archetypical sodium-ion conductor Na 3 PS 4 are not fully understood. We present here a comprehensive analysis based on diffraction (Bragg, pair distribution function), spectroscopy (impedance, Raman, NMR, INS) and ab-initio simulations aimed at elucidating the synthesis-property relationships in Na 3 PS 4. We consolidate previously reported interpretations about the local structure of ball-milled samples, underlining the sodium disorder and showing that a local tetragonal framework more accurately describes the structure than the originally proposed cubic one. Through variable-pressure impedance spectroscopy measurements, we report for the first time the activation volume for Na + migration in Na 3 PS 4 , which is ~30% higher for the ball-milled samples. Moreover, we show that the effect of ball-milling on increasing the ionic conductivity of Na 3 PS 4 to ~10-4 S/cm can be reproduced by applying external pressure on a sample from conventional high temperature ceramic synthesis. We conclude that the key effects of mechanochemical synthesis on the properties of solid electrolytes can be analyzed and understood in terms of pressure, strain and activation volume. File list (2) download file view on ChemRxiv Na3PS4_mechanical_v10.1.pdf (2.18 MiB) download file view on ChemRxiv SI_Na3PS4_mechanical_v10.1.pdf (2.38 MiB)

We report a series of ferrocene-based derivatives and their corresponding oxidized forms in which the introduction of simple electron donating groups like methyl or tert-butyl units on cyclopentadienyl-rings afford great tunability of Fe+III/Fe+II redox potentials from +0.403 V down to −0.096 V versus saturated calomel electrode. The spin forbidden d–d transitions of ferrocene derivatives shift slightly toward the blue region with an increasing number of electron-donating groups on the cyclopentadienyl-rings with very little change in absorptivity values, whereas the ligand-to-metal transitions of the corresponding ferricinium salts move significantly to the near-IR region. The electron-donating groups also contribute in the strengthening of electron density of Fe+III d-orbitals, which therefore improves the chemical stability against the oxygen reaction. Further, density functional theory calculations show a reducing trend in outer shell reorganization energy with an increasing number of the electron donating units.

Artificial multilayers offer unique opportunities for combining materials with antagonistic orders such as superconductivity and ferromagnetism and thus to realize novel quantum states. In particular, oxide multilayers enable the utilization of the high superconducting transition temperature of the cuprates and the versatile magnetic properties of the colossal-magnetoresistance manganites. However, apart from exploratory work, the in-depth investigation of their unusual properties has only just begun. Here we present neutron reflectometry measurements of a [Y(0.6)Pr(0.4)Ba(2)Cu(3)O(7) (10 nm)/La(2/3)Ca(1/3)MnO(3) (10 nm)](10) superlattice, which reveal a surprisingly large superconductivity-induced modulation of the vertical ferromagnetic magnetization profile. Most surprisingly, this modulation seems to involve the density rather than the orientation of the magnetization and is highly susceptible to the strain, which is transmitted from the SrTiO(3) substrate. We outline a possible explanation of this unusual superconductivity-induced phenomenon in terms of a phase separation between ferromagnetic and non-ferromagnetic nanodomains in the La(2/3)Ca(1/3)MnO(3) layers.

Solid electrolytes are crucial for next-generation solid-state batteries, and Na 3 PS 4 is one of the most promising Na + conductors for such applications, despite outstanding questions regarding its structural polymorphs. In this contribution, we present a detailed investigation of the evolution in structure and dynamics of Na 3 PS 4 over a wide temperature range 30 < T < 600 °C through combined experimental−computational analysis. Although Bragg diffraction experiments indicate a second-order phase transition from the tetragonal ground state (α, P4̅ 2 1 c) to the cubic polymorph (β, I4̅ 3m) above ∼250 °C, pair distribution function analysis in real space and Raman spectroscopy indicate remnants of a tetragonal character in the range 250 < T < 500 °C, which we attribute to dynamic local tetragonal distortions. The first-order phase transition to the mesophasic high-temperature polymorph (γ, Fddd) is associated with a sharp volume increase and the onset of liquid-like dynamics for sodium-cations (translational) and thiophosphate-polyanions (rotational) evident by inelastic neutron and Raman spectroscopies, as well as pair-distribution function and molecular dynamics analyses. These results shed light on the rich polymorphism of Na 3 PS 4 and are relevant for a range host of high-performance materials deriving from the Na 3 PS 4 structural archetype.

This work sheds light on the exceptional robustness of anatase TiO2 when it is downsized to an extreme value of 4 nm. Since at this size the surface contribution to the volume becomes predominant, it turns out that the material becomes significantly resistant against particles coarsening with temperature, entailing a significant delay in the anatase to rutile phase transition, prolonging up to 1000 °C in air. A noticeable alteration of the phase stability diagram with lithium insertion is also experienced. Lithium insertion in such nanocrystalline anatase TiO2 converts into a complete solid solution until almost Li1TiO2, a composition at which the tetragonal to orthorhombic transition takes place without the formation of the emblematic and unwished rock salt Li1TiO2 phase. Consequently, excellent reversibility in the electrochemical process is experienced in the whole portion of lithium content.

phase stability to strain effects and rotation/tilt degrees of freedom.

The seminal work published by Honda et al. in 1972 highlighting the photoelectrochemical water splitting by means of bandgap excitation in TiO 2 has triggered interest in this material for optoelectronic applications. [ 1 ] Waste purifi cation, fuel, and electricity production by making direct use of the sunlight are elegant and very promising smart technologies in which the anatase polymorph of TiO 2 is one leading contending semiconductor. [ 2 ] Such interest stems from a set of intrinsic specifi cities such as its earth abundance, low toxicity, low cost together with a chemical richness due to its 3d 0 electronic confi guration, which is sensitive to punctual defects and to doping. [ 3 ] This is illustrated by the recent achievements to blue shift the energy bandgap from 3.2 to 3.8 eV as a result from the electron/hole quantum confi nement experienced below a 2 nm size threshold or, inversely, to widely red shift the absorption edge to such an extent that the well-known white TiO 2 turns completely black with a bandgap of 1.54 eV. [ 4,5 ] This is the sole example of a semiconductor oxide for which the bandgap can be tuned to such an extent. In addition to bandgap engineering, with the aim to obtain optimal performance from this material, particular attention has been paid to the carefully tailor structured and nanotextured TiO 2 , as it can modify the bulk properties owing to the higher surface-to-volume ratio or improving the charge carrier transport. The most illustrative examples are: i) the lower energy surface of anatase compared with rutile, which induces a polymorph stability crossover below 11 nm where the anatase structure becomes thermodynamically the most stable; [ 6 ] ii) electrochemical lithium insertion in the denser rutile polymorph achieved in nanosized particles; [ 7 ] or iii) faster electron transport and lower recombination rate constant experienced in dye-sensitized solar cell technology. [ 8 ] Exploiting high surface area material is therefore advantageous for both fundamental and applied purposes. For this, a low temperature approach with mild conditions is required in order to achieve good control in the antagonistic processes of nucleation and particle growth. The synthesis of TiO 2 nanoparticles, in particular by hydro, solvo, or iono-thermal synthesis, sol-gel, or precipitation in aqueous media have been reported. [ 9 ] The interest for soft chemistry targets the nanostructuration and attempts to reduce the energy consumption during the chemical transformation cycle, which will translate into cost-cutting, lower energy payback times when the material is associated with thermal or sunlight conversion applications, and stands for a noticeable path to limit the anthropogenic greenhouse gas emission. Contrary to the preconceived idea that we need heating for chemical transformation, synthesis engineering conducted at room temperature still appears marginal while its The synthesis of highly divided anatase TiO 2 nanoparticles displaying 300 m 2 g −1 surface area is achieved by follow...