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This work demonstrates forming-free and self-limiting resistive switching characteristics of non-stoichiometric WO3−x-based nanoscale devices without using any selector layer. Pt/W/WO3−x/Pt cross point and crossbar devices with individual cell dimensions of 200 × 400 nm2 have been fabricated using e-beam lithography, sputtering, and lift-off processes. The devices exhibited stable multi-level bipolar resistive switching with a high on/off ratio. In the crossbar device, the programmed resistance states were clearly distinguishable in the worst-case and arbitrary-case scenarios. The present study demonstrates that CMOS process-compatible WO3−x possesses great potential for designing future nanoscale resistive random access memories for high-density memory applications. [ABSTRACT FROM AUTHOR]

Sodium-ion batteries (SIBs) are an exciting alternative to commercially dominant lithium-ion batteries for electric vehicles and other applications. However, cathodes of SIBs suffer poor kinetics, low average potential, and poor rate capability due to the large ionic radius of Na+–ions. We report an α- and β-type composite NaMn0.89Ni0.11O2 cathode with excellent electrochemical performance. The designed electrode shows a discharge capacity of 100.1 mAh g−1 with a capacity retention of about 69% and Coulombic efficiency of 98.9% even after 100 cycles at 0.05C. The diffusion coefficient of the electrode material lies in an impressive range of values of 10−06–10−11 cm2 s−1 over the state of charge. The α-phase helps get a higher diffusion coefficient, and the β-phase diminishes Jahn–Teller distortion arising from the Mn3+/4+ oxidation process, exploiting both phases' compositional and structural tolerance. The β-phase increases cycle life, and the α-phase increases kinetics. Accessing the Ni2+/4+ oxidation process increases the electrodes' average operating potential. The NaMn0.89Ni0.11O2 // HC full cell gives an average potential of 2.7 V when cycled in the potential range of 1.5–3.2 V. [ABSTRACT FROM AUTHOR]

Resistive switching (RS) in metal oxides, which offers self‐compliance and multiple resistance states without the requirement of any high voltage forming step, holds the potential of application in selector less high density resistive random access memory (RRAM) devices. Typically, operation of metal oxide‐based RS devices requires the integration of additional oxide layers or circuit elements to achieve current compliance and complicated device architecture for high‐density memory applications. In this study, a self‐compliance, and multi‐level RS is demonstrated that does not require high voltage forming in a single layer non‐stoichiometric WO3–x. This study suggests that high oxygen vacancy (VO) concentration in the pristine WO3–x layer leads to its forming‐free filamentary switching characteristics, whereas reversible formation and annihilation of an oxygen‐rich region in the filament at the WO3–x/Pt junction has been envisaged to be responsible for self‐compliance set and voltage controlled multiple reset resistance states. The results demonstrate non‐stoichiometric WO3–x with an active metal/oxide interface permeable to reversible oxygen migration can pave the way for producing high density, reliable RRAM devices. [ABSTRACT FROM AUTHOR]

We have synthesized [Bi.sub.3] [Fe.sub.4][Ga.sub.1][O.sub.12] (BIGG) films on [Gd.sub.3][Ga.sub.3][O.sub.12] and [Gd.sub.3] [(ScGa).sub.5] [O.sub.12] substrates by a pulsed laser deposition technique. X-ray diffraction and rocking curve analyses confirm the epitaxial quality of the films with a lattice constant close to 12.61 [+ or -] 0.01 A. Compared with that of a bismuth iron garnet [Bi.sub.3][Fe.sub.5] [O.sub.12] (BIG) film, the bandwidth of the BIGG transmittance (T) spectrum is extended and its left edge shifted down in wavelength by approximately 50 nm. This enables its Faraday rotation [[theta].sub.F] and switching speed to be tested at a wavelength of 532 nm. While BIGG film has a Faraday rotation angle slightly less than that of BIG film, its magnetooptical figure of merit, 2|[[theta].sub.F] d|/-ln (T%), is greatly improved to a typical value ~1.8 times larger than that of the BIG film. Further, the high-speed pulse response time of the BIGG film reaches 2.4 ns with a 1 mm aperture size at the wavelength of 532 nm. Index Terms--Faraday effect, garnet films, pulsed laser deposition, ultrafast switching.

Sodium-ion batteries have emerged as an exciting alternative to commercially dominant lithium-ion batteries for electric vehicles and other applications. However, cathodes of sodium-ion batteries (SIBs) suffer poor kinetics and rate capability due to the large ionic radius of Na+–ions. We report an α– and β–type composite NaMn0.89Co0.11O2 cathode with excellent electrochemical performance. The designed electrode exhibits a discharge capacity of 110.5 mAh g−1 with a capacity retention of about 68% and Coulombic efficiency of 98.9% even after 120 cycles at 0.05C. Diffusion coefficient of the designed material shows 10−07–10−12 cm2 s−1 for over the state of charge. The α–phase provides a higher diffusion coefficient, and β–phase alleviates Jahn–Teller distortion arising from the Mn3+/4+ oxidation process, exploiting compositional and structural tolerance of both phases. The β–phase reduces Jahn–Teller distortion and thereby increases cycle life, and the α–phase helps get better kinetics. The NaMn0.89Co0.11O2 // HC full cell gives an average potential of 2.45 V when cycled in 1.5–3.2 V. [ABSTRACT FROM AUTHOR]

The magnetic anisotropic parameters and spin-wave relaxation of thin films of the ferromagnetic half-metallic [Sr.sub.2]FeMo[O.sub.6] is examined by ferromagnetic resonance method. The spin relaxation time is estimated from the analysis of the angular dependence of peak-to-peak linewidth, which has led to Gilbert damping.

This study aims to evaluate various polymorphs of Fe2O3 (γ- and α-types) as anode material for sodium-ion batteries and their conversion mechanisms. In this work, pulsed laser deposition (PLD) was used to successfully fabricate Fe2O3 (both γ- and α-types) thin film followed by the electrochemical investigation as anode material for a sodium-ion battery. The γ-Fe2O3 shows high reversibility than α-Fe2O3 while discharging at a deep discharge voltage of 0.01 V. The α-Fe2O3 changes to Fe3O4 during sodium extraction, while the γ-Fe2O3 remains unaltered upon cycling. The γ-Fe2O3 shows high electrochemical performance regarding cycle life and discharge capacity than α-Fe2O3 (considering up to 80 cycles). The discharge capacity of γ-Fe2O3 is 335.2 mAh g−1 and of α-Fe2O3 is 248.7 mAh g−1 for the 1st cycle at a current rate of 475 mA g−1. The achieved superior performance of γ-Fe2O3 is credited to the reversible reaction path and binder-free nature of the thin film. [ABSTRACT FROM AUTHOR]

We investigated the magnetic anisotropic parameters and spin-wave relaxation of thin films of the ferromagnetic half-metallic Sr2FeMoO6 by ferromagnetic resonance technique. The resonance field and linewidth were recorded as a function of relative angle between applied magnetic field and crystallographic axes of the sample. The resonance field varies sinusoidally and considerable linewidth broadening occurs when the applied field is rotated parallel to the sample plane. The results are described using higher order components of anisotropy fields. We obtain the values of the cubic anisotropic field, 2K4∥/M=0.096 11 T, the effective demagnetization field, 4πM-2K2⊥/M=0.1216 T, and the planar anisotropic field, 2K4⊥/M=-0.108 T. Moreover, we estimated the spin relaxation time (damping factor) from the analysis of the angular dependence of peak-to-peak linewidth, leading to an intrinsic value of α∼0.000 25 (Gilbert damping). [ABSTRACT FROM AUTHOR]

Sodium-ion batteries are the commercially and environmentally viable next-generation candidates for automobiles. Structural and electrochemical aspects are greater concerns towards the development of a stable cathode material. Selecting transition metals and their composition greatly influences charge order, superstructures, and different voltage plateaus. This, in turn, influences transport properties and cyclic performance. This article aims to study the electrochemical performance, diffusivity, and structural stability of Nax[MyMn1−y]O2 (M = Fe, Ni) as cathode. Both experimental and DFT-based calculations apprehend the voltage plateaus due to redox reactions. The rate of cycling and the initial structure also influence the cycle life. The diffusion coefficient of P2-type Na0.67Fe0.5Mn0.5O2 for Mn3+/4+ redox reactions is more than that of the O3-type NaFe0.5Mn0.5O2 while it is less for Fe3+/4+ redox reactions, because of structural transition. The diffusion coefficient of NaNi0.5Mn0.5O2 is less for Ni2+/4+ redox reaction and is up to the order of 10−11 cm2 s−1. [ABSTRACT FROM AUTHOR]