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The stochastic computing (SC) has been proven to be an energy-efficient way to perform neural network. In this study, we propose a field-free voltage-controlled spintronics SC system based on the magnetic tunnel junction (MTJ). We observe a stochastic switching behavior of the MTJ and that it could be controlled by the voltage applied on the device. The voltage-controlled stochastic switching behavior is used to encode numbers ranging from 0 to 1 into a series of random bit-streams in the SC system. Furthermore, the handwritten recognition task is performed on the MTJ-based SC system, achieving a 95% maximum accuracy, which is comparable with the floating-point based neural network. Our work provides inspiration for the energy-efficient neural network systems. [ABSTRACT FROM AUTHOR]

Bulk PtBi2 has attracted much attention for its topological semi-metallic electronic properties and highly promising applications in spintronics. Here, we report large spin–orbit torque (SOT) efficiency in the sputtered PtBi2 alloy with the trigonal-phase. From spin–torque-induced ferromagnetic resonance measurements, the SOT efficiency of 5 nm PtBi2 is estimated to be ∼0.2. Moreover, the spin Hall conductivity of PtBi2 [∼1 × 105 ℏ/2e (Ω m)−1] is comparable to that of topological materials, such PtTe2 and Bi2Te3. The PtBi2 film has much lower resistance than that of Bi-based topological materials, which makes it a useful candidate for application. The results suggest that the PtBi2 alloy is promising for applications in magnetic memory and logic devices driven by SOT. [ABSTRACT FROM AUTHOR]

In this work, the atomistic simulation method based on Pedone model is applied to observe the concerted motion of lithium-ions in the perfect lattice of possible Li9Cr3(P2O7)3(PO4)2 cathode material. The simulation is carried out at a series of increasingly elevated temperatures in a super cell containing 27 unit cells. The superimposed Li+ trajectory at all timeframes offers an intuitive, reliable image of the Li+ migration in the crystal lattice. It reveals that lithium-ion propagates in a–b plane in an isotropic way and the propagation along the c axis is negligible. A typical lithium-ion migration path along the a or b axis can be described as migrating consecutively in the repeated sequence of Li1, Li3, Li1, and Li2. The energy barrier of Li9Cr3(P2O7)3(PO4)2 cathode material is about 0.345 eV and the estimated lithium-ion diffusion coefficients at room temperature are estimated at ca. 1.96 × 10−9 cm2 s−1. Compared with those intensively investigated cathode materials for lithium-ion batteries, which are normally considered to be highly potential or already in practical use, the lithium-ion conduction in the crystal grain for Li9Cr3(P2O7)3(PO4)2 cathode material is comparable or even superior. Therefore, the Li+ mobility is sufficiently high to exhibit good performances as a cathode material for lithium-ion batteries. More researches concerning the preparation, phase transformation, doping, surface modification, and the characterization of electro-chemical performance are urgently needed. [ABSTRACT FROM AUTHOR]

Aqueous magnesium ion batteries have been identified as potential electrochemical energy storage system due to their similar electrochemical properties to lithium, safety, high abundance, and low cost. Here, micron-sized Na0.7MnO2.05 is prepared by a facile sol-gel method used for cathode material in aqueous magnesium ion batteries. XRD, XPS, SEM, TEM, and EDS were used to test the composition, structure, and morphology of Na0.7MnO2.05. Na0.7MnO2.05 material is electro-chemical active although the intercalation/deintercalation is much difficult for Mg2+. The reversible specific capacities of the Na0.7MnO2.05 cathode material are estimated to be ca. 40, 35, 22, and 13 mAh·g−1 at the current density of 1 C, 2 C, 5 C, and 10 C, respectively. When the current density comes back to 1 C, the charge capacities recover to 40 mAh·g−1. Furthermore, EIS and GITT measured show that the diffusion coefficient of Mg2+ ion in lattice of Na0.7MnO2.05 varies from 2.17 × 10−11 cm2·s−1 to 7.81 × 10−11 cm2·s−1 in charge process and changes from 6.34 × 10−12 cm2·s−1 to 7.14 × 10−11 cm2·s−1 in discharge process. [ABSTRACT FROM AUTHOR]