With the advent of pure-spin-current sources, spin-based electronic (spintronic) devices no longer require electrical charge transfer, opening new possibilities for both conducting and insulating spintronic systems. Pure spin currents have been used to suppress noise caused by thermal fluctuations in magnetic nanodevices, amplify propagating magnetization waves, and to reduce the dynamic damping in magnetic films. However, generation of coherent auto-oscillations by pure spin currents has not been achieved so far. Here we demonstrate the generation of single-mode coherent auto-oscillations in a device that combines local injection of a pure spin current with enhanced spin-wave radiation losses. Counterintuitively, radiation losses enable excitation of auto-oscillation, suppressing the nonlinear processes that prevent auto-oscillation by redistributing the energy between different modes. Our devices exhibit auto-oscillations at moderate current densities, at a microwave frequency tunable over a wide range. These findings suggest a new route for the implementation of nanoscale microwave sources for next-generation integrated electronics.

The preparation and electrochemical characterization of a new material consisting of carbon coated ZnFe 2 O 4 nanoparticles is presented. This material, which offers an interesting combination of alloying and conversion mechanisms, is capable of hosting up to nine equivalents of lithium per unit formula, corresponding to an exceptional specifi c capacity, higher than 1000 mAh g − 1 . Composite electrodes of such a material, prepared using environmentally friendly sodium carboxymethyl cellulose as binder, showed the highest, ever reported, specifi c capacity and high rate performance upon long-term testing. Furthermore, in situ X-ray diffraction analysis allowed identifying the reduction process occurring upon initial lithiation. 514 wileyonlinelibrary.com

Herein, we present a new synthesis method for transition-metal-doped zinc oxide nanoparticles utilized and characterized for the first time as anode material for lithium-ion batteries. In fact, the introduction of a transition metal (for instance, iron or cobalt) into the zinc oxide lattice results in an advanced performance with reversible lithium storage capacities exceeding 900 mAh g–1, i.e., more than twice that of graphite. In situ XRD analysis reveals the electrochemical reduction of the wurtzite structure and the reversible formation of a LiZn alloy. The additional application of a carbon coating of such nanoparticles enables further improvement in terms of capacity retention and high rate (dis)charge capability. Moreover, the newly developed, simple, and environmentally friendly synthesis of these n-type doped nanoparticles is considered to be also applicable to other transition metals, presumably showing comparable electrochemical performances.

No abstract

Polydomain tetragonal (t) zirconia was deformed in compression along a ͗100͘ orientation at various temperatures between 500°and 1400°C. The stress-strain curves showed a plateau corresponding to ferroelastic deformation, followed by plastic deformation at a higher yield stress level. In both ranges, the strain-rate sensitivity of the stress was measured by stressrelaxation tests. The microstructure of the tetragonal domains after ferroelastic deformation and the dislocation substructure were studied by transmission electron microscopy in a highvoltage electron microscope. As expected, ferroelastic deformation suppressed the tetragonal variant with its c-axis parallel to the loading direction. The dislocation structure consisted of intersecting dislocations on different slip systems with strongly bowed-out segments. The microprocesses of deformation are discussed here by comparing the deformation data with those of cubic zirconia deformed in the same orientation and based on the observed microstructure. The particular microstructure of t zirconia seems to prevent recovery, so that the high flow stress of ϳ700 MPa is preserved up to 1400°C.