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Andreev reflection at a Pb/CrO(2) point contact has been used to determine the spin polarization of single-crystal CrO(2) films made by chemical vapor deposition. The spin polarization is found to be 0.96 +/- 0.01, which confirms that CrO(2) is a half-metallic ferromagnet, as theoretically predicted.

Developing a stable and safe electrolyte that works at voltages as high as 5 V is a formidable challenge in present Li-ion-battery research because such high voltages are beyond the electrochemical stability of the conventional carbonate-based solvents available. In the past few years, extensive efforts have been carried out by the research community toward the exploration of high-voltage electrolytes. In this review, recent progress in the study of several promising high-voltage electrolyte systems, as well as their recipes, electrochemical performance, electrode compatibility, and characterization methods, are summarized and reviewed. These new electrolyte systems include high-voltage film-forming additives and new solvents, such as sulfones, ionic liquids, nitriles, and fluorinated carbonates. It appears to be very difficult to find a good high-voltage (∼5 V) electrolyte with a single-component solvent at the present stage. Using mixed fluorinated-carbonate solvents and additives are two realistic solutions for practical applications in the near term, while sulfones, nitriles, ionic liquids and solid-state electrolyte/polymer electrolytes are promising candidates for the next generation of high-voltage electrolyte systems.

Rapid development of both efficiency 1 and stability 2 mean that perovskite solar cells are at the forefront of emerging photovoltaic technologies. State-of-the-art cells exhibit voltage losses 3-8 approaching the theoretical minimum and near-unity internal quantum efficiency 9-13 , but conversion efficiencies are limited by the fill-factor (FF < 83%, below the Shockley-Queisser limit of ~90%). This limitation results from non-ideal charge transport between the perovskite absorber and the cell's electrodes 5,8,13-16 . Reducing the electrical series resistance of charge transport layers is therefore crucial for improving efficiency. Here we introduce a reverse-doping process to fabricate nitrogen-doped titanium oxide electron transport layers with outstanding charge transport performance. By incorporating this charge transport material into perovskite solar cells, we demonstrate 1cm 2 cells with FFs >86%, and an average FF ~ 85.3%. We also report a certified steady-state efficiency record of 22.6% for a 1cm 2 cell (23.33% ± 0.58% from reverse current-voltage scan).Nitrogen-doped titanium oxide (titanium oxynitride, TiO x N y ) has been widely investigated for photocatalysis 17,18 , but rarely in perovskite solar cells (PSCs). PSCs incorporating solution-processed TiO x N y have been reported, but device performances have

A new current induced spin-torque transfer effect has been observed in a single ferromagnetic layer without resorting to multilayers. At a specific current density of one polarity injected from a point contact, abrupt resistance changes due to current-induced spin wave excitations have been observed. The critical current at the onset of spin-wave excitations depends linearly on the external field applied perpendicular to the layer. The observed effect is due to current-driven heterogeneity in an otherwise uniform ferromagnetic layer. 75.30.Ds, 73.40.Jn Typeset using REVT E X 1

We report on structural, magnetic, transport, and spin-polarization measurements of the Heusler alloys Co 2 MnSi and NiMnSb. Laue diffraction patterns confirm the single-crystal nature of Co 2 MnSi. Roomtemperature transport measurements show a negative magnetoresistance in NiMnSb. Point-contact Andreev reflection measurements of the spin polarization yield polarization values for Co 2 MnSi and NiMnSb of 56% and 45%, respectively. Temperature dependence of resistivity for Co 2 MnSi reveals a relatively large residual resistivity ratio ( 293 K / 5 K ) typical of single-crystal Heusler alloys. In NiMnSb, resistivity and magnetization as a function of temperature show evidence of a magnetic phase transition near 90 K.

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We demonstrate the injection of spin-polarized electrons into paramagnetic Au nanowires by driving an electric current from a ferromagnetic permalloy (Py) electrode. The nonequilibrium spin accumulation in Au results in a difference between the chemical potentials for spin-up and spin-down electrons that is detected as a field-dependent voltage signal using a second Py electrode. The magnitude of the voltage contrast (&gt;10%) and its coincidence with the magnetic switching of the Py electrodes attest to the spin-sensitive origin of the signals. By increasing the separation of the Py injector and detector, we observe an exponential decay of the spin signals. The measurements yield a spin-diffusion length of 63±15nm and an injected spin polarization of 3% in Au at 10 K.