Charge-orbital density wave and superconductivity in the strong spin-orbit coupled IrTe2:Pd

Using transmission electron microscopy, the anomalies in resistivity and magnetic susceptibility at ~262 K in IrTe2 are found to accompany the superlattice peaks with q[over q=(1/5,0,-1/5). The wave vector is consistent with our theoretical calculation for the Fermi surface nesting vector, indicating that the ~262 K transition is of the charge-orbital density wave (DW) type. We also discovered that both Pd intercalation and substitution induce bulk superconductivity with T(c) up to ~3 K, which competes with DW in a quantum critical pointlike manner.     

Electric field control of nonvolatile four-state magnetization at room temperature

We find the realization of large converse magnetoelectric (ME) effects at room temperature in a magnetoelectric hexaferrite Ba0.52Sr2.48Co2Fe24O41 single crystal, in which rapid change of electric polarization in low magnetic fields (about 5 mT) is coined to a large ME susceptibility of 3200 ps/m. The modulation of magnetization then reaches up to 0.62μ(B)/f.u. in an electric field of 1.14 MV/m. We find further that four ME states induced by different ME poling exhibit unique, nonvolatile magnetization versus electric field curves, which can be approximately described by an effective free energy with a distinct set of ME coefficients.     

Multi-stacked organic light-emitting diodes using zinc oxide nanoparticle interfacial layers

Stacked organic light-emitting diodes (SOLEDs) with 30-nm nanoparticle (NP) interfacial layers were investigated. Zinc oxide (ZnO) was used as an interfacial layer between two green polymer (GP) layers. SOLEDs with NP interfacial layers had higher device efficiency than did a single-unit device due to the high probability of exciton recombination that originated from the Auger electron-assisted energy up-conversion process. Although the current density and luminance of SOLEDs with ZnO NP interfacial layers were smaller than those of the reference device, the efficiency was doubled because of the big band alignment difference and the large band gap between GP and ZnO NP interfacial layers, which induced more radiative-exciton recombination.     

Physical and electrical properties of band-engineered SiO2/(TiO2) x (SiO2)1−x stacks for nonvolatile memory applications

In our study, the physical properties of (TiO₂) _x (SiO₂)_1?x , including band-gap, band-offset, and thermal stability and the electrical properties of band-engineered SiO₂/(TiO₂) _x (SiO₂)_1?x tunnel barrier stacks, including the tunneling current and charge-trapping characteristics for applications to nonvolatile memory devices were investigated. It was observed that the band-gap and band-offset of (TiO₂) _x (SiO₂)_1?x can be controlled by adjustment in the composition of the (TiO₂) _x (SiO₂)_1?x films. Ti-silicate film with TiO₂:SiO₂ cycle ratio of 1:5 was maintained in an amorphous phase, even after annealing at 950 °C. The tunneling current of the band-engineered SiO₂/(TiO₂) _x (SiO₂)_1?x stacked tunnel barrier was larger than that of a single SiO₂ barrier under a higher external bias, while the tunneling current of a SiO₂/(TiO₂) _x (SiO₂)_1?x stacked tunnel barrier under a lower external bias was smaller. Charge-trapping tests showed that the voltage shift for SiO₂/(TiO₂) _x (SiO₂)_1?x is slightly larger than that for single SiO₂.     

Structural studies of AgSbTe2 under pressure: Experimental and theoretical analyses

The crystal structure of AgSbTe₂ has been refined using first-principles calculations, from which the ordering of the cations, Ag and Sb, was confirmed. The spontaneous formation of two (D4 and L1₁) phases at ambient and elevated pressure was demonstrated theoretically. The compound was also prepared and its high-pressure structural deformation sequence, ranging from ambient to 50.9 GPa, was observed with synchrotron radiation at room temperature. The compound underwent a pressure-induced amorphization (PIA) at 24.6 GPa and then started recrystallizing at 49.2 GPa. The bulk modulus (B₀) and pressure derivative of the bulk modulus (B_p) were determined experimentally to be 56.3 ± 5.1 GPa and 4.3 ± 0.8, respectively. We suggest that large displacements of Te atoms to Ag vacancy positions are responsible for PIA and the recrystallization.     

Simultaneous Determination of Acetylsalicylic Acid and Caffeine in Pharmaceutical Formulation by First Derivative Synchronous Fluorimetric Method

A sensitive, rapid, and specific assay has been developed for the simultaneous determination of acetylsalicylic acid and caffeine in commercial tablets based on their natural fluorescence. The mixture of these drugs was resolved by first derivative synchronous fluorimetric technique using two scans. At Δλ=106 nm, using first derivative synchronous scanning, only acetylsalicylic acid yields a detectable signal at 316 nm (peak to zero method) which is unaffected by caffeine. At Δλ=30 nm, the signal of caffeine at 288 nm (peak to zero method) is not affected by acetylsalicylic acid. The range of application is between 0.021 and 41.62 μg ml⁻¹ (correlation coefficient, R=0.9995) for acetylsalicylic acid and between 0.4486 and 44.86 μg ml⁻¹ (correlation coefficient, R=0.99786) for caffeine. The recovery range of 98.40–102% for acetylsalicylic acid and 90–100.5% for caffeine from their synthetic mixture was reported. Overall recovery of both compounds about 97–99% for acetylsalicylic acid and 97–98% for caffeine was obtained from real sample analysis. The detection limits are 0.0013 μg ml⁻¹ and 0.0306 μg ml⁻¹ for acetylsalicylic acid and caffeine, respectively. The relative standard deviation (n=10) for 20 μg ml⁻¹ of acetylsalicylic acid is 2.75% and for 2.2 μg ml⁻¹of caffeine is 1.7%.     

Black phosphorus saturable absorber for ultrafast mode‐locked pulse laser via evanescent field interaction

Black phosphorus, or BP, has found a lot of applications in recent years including photonics. The most recent studies have shown that the material has an excellent optical nonlinearity useful in many areas, one of which is in saturable absorption for passive mode‐locking. A direct interaction scheme for mode‐locking, however, has a potential to optically cause permanent damage to the already delicate material. Evanescent field interaction scheme has already been proven to be a useful method to prevent such danger for other 2‐dimensional nanomaterials. In this report, we have utilized the evanescent field interaction to demonstrate that the optical nonlinear characteristics of BP is sufficiently strong to use in such an indirect interaction method. The successful demonstration of the passive mode‐locking operation has generated pulses with the pulse duration, repetition rate, and time bandwidth product of 2.18 ps, 15.59 MHz, and 0.336, respectively.