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The formation of octonary DyErGdHoLuScTbY and senary DyGdHoLaTbY and ErGdHoLaTbY high-entropy alloys (HEAs) with the hexagonal close-packed (HCP) structure was reported in this study. Experiments using scanning electron microscopy and x-ray diffraction confirmed the single HCP solid solution in the as-cast state for these three HEAs if the presence of minor rare-earth oxides due to contamination from processing is ignored. The measured compressive yield stress values for these HEAs at room temperature are 245, 205, and 360 MPa for the ErGdHoLaTbY, DyGdHoLaTbY, and DyErGdHoLuScTbY HEAs, respectively. The corresponding solid solution strengthening contributions for these HEAs were estimated using a simple elastic model, and the resulting contributions were 28 MPa, 27 MPa, and 42 MPa for the three aforementioned HEAs. [ABSTRACT FROM AUTHOR]

Epilepsy is a serious neurological condition caused by a sudden abnormality of brain neurons. An accurate epilepsy detection based on electroencephalogram (EEG) signals can provide vital information for diagnosis and treatment. In this study, we propose a lightweight automatic epilepsy detection system with artificial neural network based on our as-fabricated neuromorphic chip. The proposed system utilizes a neural network model to achieve high-accuracy detection without the need for epilepsy-related prior knowledge. The model uses a filter module and a convolutional neural network to preprocess the raw EEG signal and uses a long short-term memory recurrent neural network and a fully connected network as the classifier. In the examination, the classification accuracy of the normal cases and seizures approaches 99.10%, and the accuracy of the normal cases, and interictal and seizure cases can reach 94.46%. This design provides possible epilepsy detection in wearable or portable devices. [ABSTRACT FROM AUTHOR]

Voltage control of the magnetic anisotropy (VCMA) effect enables a voltage-mediated magnetization switching mechanism for lower-power applications. In this work, we experimentally investigate the characteristics of VCMA-induced switching and we observe a clear decrease in the critical switching voltage ( V c ) at elevated temperatures. A 50% reduction in V c is quantified when increasing the ambient temperature (T) from 300 K to 360 K. Such a T-dependence of V c is well explained with the variations of saturation magnetization ( M S ), interfacial anisotropy ( K i ), and VCMA coefficient (ξ). In addition, the dependences of these properties on temperature are well fitted and explained with the power law of M S (T). Our findings on the T-dependent magnetic and switching characteristics of VCMA are of technological importance for implementing VCMA in magnetic random access memory (MRAM) applications. [ABSTRACT FROM AUTHOR]

We study the characteristics of the precessional switching induced by voltage control of magnetic anisotropy (VCMA) in back-end-of-line (BEOL)-compatible perpendicular magnetic tunnel junction devices. Using micromagnetic simulation, we find three operation regimes differentiated by zero excess energy, lower boundary, zero energy barrier, and upper boundary. Experimentally, the switching speed (fs) is characterized by two phases: non-precession and acceleration. Non-precession is a thermal mediated phase, where fs cannot be deduced, while in acceleration, both the higher electric field (EF) and in-plane field (Bx) increase fs progressively. We find that the intrinsic thresholds can be retrieved by linear extrapolation of fs as a function of EF. Those thresholds and experimental results are in good agreement with the simulation. In addition, we numerically calculate the characteristic switching speed of 2γ*mz*Bx and verify it experimentally. This work provides insights into the VCMA-induced precessional switching, including detailed understandings of the switching mechanism and modeling of switching speed for reliable write duration control for practical applications. [ABSTRACT FROM AUTHOR]

Analogous device parameters in both the parallel (P) and anti-parallel (AP) states ensure a symmetric spin-transfer-torque magnetic random-access memory operation scheme. In this study, however, we observe an increasing asymmetry in the performance metrics with operating temperature of the bottom-pinned perpendicular magnetic tunnel junction (p-MTJ) devices. A temperature-dependent increase in the contribution of the stray field is observed in the tunneling magnetoresistance loop analysis. The switching current for P-to-AP decreases by 30% in the thermally activated switching regime by increasing the temperature from 300 K to 400 K, while it remains similar for AP-to-P. In addition, with the same temperature range, the thermal stability factor for the P state decreases 20% more than that for the AP state. We attribute those observations to the increase in the overcompensation of the stray field from the synthetic anti-ferromagnet structure. Saturation magnetization (MS) of the [Co/Pt]x-based multilayers is much less affected by temperature [MS(400 K)/MS(300 K) = 97%] compared to that of the CoFeB-based multilayers (88%). Such an impact can be more severe during the electrical switching process due to the Joule heating effect. These results suggest that, to understand and to evaluate the performance in a wide range of temperatures, it is crucial to consider the contribution of the entire magnetic components in the p-MTJ stack. [ABSTRACT FROM AUTHOR]

We have compared the spin orbit torque (SOT) induced magnetization switching in Pt/Co/Pt/ Y3Fe5O12 (YIG) and Pt/Co/Pt/SiO2 multilayers. The critical switching current in Pt/Co/Pt/YIG is almost half of that in Pt/Co/Pt/SiO2. Through harmonic measurements, we demonstrated the enhancement of the effective spin Hall angle in Pt/Co/Pt/YIG. The increased efficiency of SOT is ascribed to the nonequilibrium proximity effect at the Pt/YIG interface, which suppresses the spin current reflection and enhances the effective spin accumulation at the Co/Pt interface. Our method can effectively reduce the switching current density and provide another way to modulate SOT. [ABSTRACT FROM AUTHOR]

The evolution of a small spatially periodic perturbation in the electron velocity distribution function in collisionless plasma is reconsidered by numerically solving the Vlasov and Poisson equations. The short as well as long time behaviors of the excited oscillations and damping/ modulation are followed. In the small but finite-amplitude excited plasma wave, resonant electrons become trapped in the wave potential wells and their motion affects the low-velocity electrons participating in the plasma oscillations, leading to modulation of the latter at an effective trapping frequency. It is found that the phase space of the resonant and low-velocity electrons becomes chaotic, but then self-organization takes place but remains fine-scale chaotic. It is also found that as long as particles are trapped, there is only modulation and no monotonic damping of the excited plasma wave. The modulation period/amplitude increases/decreases as the magnitude of the initial disturbance is reduced. For the initial and boundary conditions used here, linear Landau damping corresponds to the asymptotic limit of the modulation period becoming infinite, or no trapping of the resonant electrons. [ABSTRACT FROM AUTHOR]

To probe the origin of p-type conductivity in Sb-doped ZnO, a careful and detailed synchrotron radiation study was performed. The extended X-ray absorption fine structure and X-ray photoelectron spectroscopy investigations provided the evidence for the formation of the complex defects comprising substitution Sb ions at Zn sites (SbZn) and Zn vacancies within the Sb-doped ZnO lattice. Such complex defects result in the increases of Sb-O coordination number and the Sb valence and thereby lead to the p-type conductivity of Sb-doped ZnO. The back-gate field-effect-transistors based on single nanorod of Sb-doped ZnO were constructed, and the stable p-type conduction behavior was confirmed. [ABSTRACT FROM AUTHOR]

A guidance and collimation scheme for fast electron beam in a traverse periodic quasi-static electromagnetic field array is proposed with the semi-analytic method and the particle-in-cell simulation. The sheath electric fields on the surfaces of nanowires and the magnetic fields around the nanowires form a traverse periodic quasi-static electromagnetic field array. Therefore, most of the fast electrons are confined at the nanowire surfaces and transport forward. More importantly, due to the divergent property of the beams, the magnitudes of the generated fields decrease with the target depth. The lateral momenta of the electrons convert into the forward momenta through Lorenz force, and they cannot recover their initial values. Therefore, the fast electrons can be guided and collimated efficiently in the gaps between the nanowires. In our particle-in-cell simulations, the observed guiding efficiency exceeds 80% compared with the reference target. [ABSTRACT FROM AUTHOR]

Megaelectronvolt (MeV) ion beams with low divergence (10°) are experimentally generated from a thin foil irradiated by an ultrahigh-contrast laser at a peak intensity of ∼1018 W/cm2. The high-contrast (∼1011) laser is obtained with a pulse cleaner based on noncollinear optical-parametric amplification and second-harmonic generation processes. The effects of the foil density, foil thickness, as well as the density gradients at the front and back sides of the foil are investigated with two-dimensional particle-in-cell simulations. The beam parameters of maximum energy and divergence strongly depend on the density gradients at the back side of the foil. [ABSTRACT FROM AUTHOR]

A new type of the integrator system with the low drift characteristic has been developed to accommodate the long pulse plasma discharges on Experiment Advanced Superconductor Tokamak (EAST). The integrator system is composed of the Ethernet control module and the integral module which includes one integrator circuit, followed by two isolation circuits and two program-controlled amplifier circuits. It compensates automatically integration drift and is applied in real-time control. The performance test and the experimental results in plasma discharges show that the developed integrator system can meet the requirements of plasma control on the accuracy and noise level of the integrator in long pulse discharges. [ABSTRACT FROM AUTHOR]

This article gives the absolute calibration of two types phosphor screens (DRZ) that were used to detect and characterize electron bunches driven by laser-plasma accelerator. The test was performed with picoseconds electron bunch at a radio frequency linear electron accelerator in Tsinghua University. The photons emitted from DRZ screens showed good linear responses to the charge of incident electron bunch and cosine angular distribution in space. An energy conversional efficiency of effective scintillant matter was also calculated. [ABSTRACT FROM AUTHOR]

Single-phase PbPd0.81Co0.19O2 film with a body-centered orthorhombic structure was prepared using the sol-gel spin-coating technique and an oxidation treatment. Film resistivity has a power dependence on temperature. The insulator-metal transition temperature was 358 K, markedly higher than the reported values of similar material systems. Ferromagnetism and superparamagnetism coexisted in the film and the ferromagnetism persisted up to 380 K. As temperature increased, the notable increasing tendencies were found for the film's saturation magnetization and for the magnetic field where saturation magnetization decreases abruptly. The special spin gapless band structure and the film's nanograin microstructure are likely responsible for these interesting properties. [ABSTRACT FROM AUTHOR]

The erasing characteristics of Cu2O metal-insulator-metal resistive switching memory were measured on a 64 Kb memory test array. The erasing yield reaches the maximum at an optimal erasing voltage. Effective erasing requires a threshold current compliance that is higher for shorter pulse width. The erasing current and erasing power both depend strongly on the on-state before erasing, while the erasing voltage is essentially unaffected. Erasing appears to be a power-driven process, which may be related to the thermal effect of power dissipation. The experimental data and analysis suggest that erasing can be explained by field-assisted thermal emission of trapped charges. [ABSTRACT FROM AUTHOR]

The Cu2O metal-insulator-metal (MIM) resistive switching memory was characterized on a 64 kb memory test array. The switching properties are consistent with the proposed switching model of conductivity modulation by a charge trapping process. Retention, programing characteristics, and temperature effects are analyzed based on the switching model. The measured characteristics and the switching model for Cu2O MIM are compared with those of other resistive switching materials. The statistical characteristics provide essential evidence for analysis of the switching mechanism and evaluation of the memory devices. [ABSTRACT FROM AUTHOR]

We have presented the voltage-controlled tuning of plasmonic response of absorption spectra of gold nanorods in liquid crystals. We observe that gold nanorods can be aligned along the rubbed polyimide substrate before applying external voltage. It is found that the transverse mode of gold nanorods shows a blueshift or a redshift when rotating the analyzer parallel or perpendicular to the rubbing direction, respectively, while all longitudinal modes display a redshift behavior. This work offers an easy way to tune the transverse and longitudinal modes of gold nanorods simultaneously, which makes it feasible to establish the color tunable devices. [ABSTRACT FROM AUTHOR]

The ordering temperature of FePt films grown on PtMn underlayers was reduced due to phase transformation of the PtMn L10 phase. The in-plane coercivity of 10 nm FePt on 50 nm PtMn underlayers was 7688 Oe after annealing at 325 °C. An exchange field of 554 Oe was also observed, which indicates that PtMn may not only induce the ordering of FePt at a reduced temperature, but also may provide extra anisotropy. A large coercivity of 10500 Oe can be achieved for 35 nm FePt films on PtMn underlayers after 325 °C annealing. [ABSTRACT FROM AUTHOR]

We report a 3D microfluidic device with 32 detection channels and 64 sheath flow channels and embedded microball lens array for high throughput multicolor fluorescence detection. A throughput of 358 400 cells/s has been accomplished. This device is realized by utilizing solid immersion micro ball lens arrays for high sensitivity and parallel fluorescence detection. High refractive index micro ball lenses (n = 2.1) are embedded underneath PDMS channels close to cell detection zones in channels. This design permits patterning high N.A. micro ball lenses in a compact fashion for parallel fluorescence detection on a small footprint device. This device also utilizes 3D microfluidic fabrication to address fluid routing issues in two-dimensional parallel sheath focusing and allows simultaneous pumping of 32 sample channels and 64 sheath flow channels with only two inlets. [ABSTRACT FROM AUTHOR]