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The layered transition metal dichalcogenide has attracted tremendous attention for its unique structure and electrical and optoelectronic properties. As an emerging two-dimensional material, PdSe2 plays a key role in optoelectronic applications due to its distinct optical and tunable electrical properties. The carrier dynamic and low-frequency phonon modes and how they evolve with the number of layers are important for future device fabrication in photonics, optoelectronics, and nanomechanics. Here, by employing ultrafast optical pump–probe spectroscopy, we have investigated systematically the photocarrier dynamics as well as the thickness dependent interlayer coherent phonon modes in PdSe2 films. Two low-frequency phonon modes in PdSe2 films are identified after photoexcitation at 780 nm. The higher-frequency mode is ascribed to the interlayer breathing mode, and the lower one is assigned to the standing wave mode, and both of the mode frequencies decrease with increasing the number of layers of films. Analysis based on simple one-dimensional chain model produces interlayer force constant K = 5.74 × 1019 N/m3 for the interlayer breathing mode, and sound velocity of v = 8.27 × 104 cm/s for the standing wave mode in PdSe2 film. Our experimental finding paves the way for designing and developing PdSe2-based optoelectronic and nanomechanic devices.

Nanopores in graphene membranes can potentially offer unprecedented spatial resolution for single molecule sensing, but their fabrication has thus far been difficult, poorly scalable, and prone to contamination. We demonstrate an in-situ fabrication method that nucleates and controllably enlarges nanopores in electrolyte solution by applying ultra-short, high-voltage pulses across the graphene membrane. This method can be used to rapidly produce graphene nanopores with subnanometer size accuracy in an apparatus free of nanoscale beams or tips.

The material of methylammonium lead iodide, CH3NH3PbI3 (MAPbI3), has shown significant promise in solar cell applications. A way to infer the microscopic scattering mechanism(s) in MAPbI3 is through the measured temperature dependence of carrier mobility. To this end, how does the carrier effective mass depend on temperature, m* = m*(T), is a useful information since the mobility is a function of m*. By atomistic first principles, we report the calculated m*(T) due to the thermal expansion of MAPbI3 materials, in the experimentally relevant range of 130 K to room temperature. The calculated results suggest m* = m*(T) to be linear in T. The increase of m* versus temperature is predominantly due to the expansion of the longitudinal atomic spacing that weakens the s/p hybridization between the I/Pb atoms.

Cooling magnetic field dependence of magnetic phase transition has been observed in Y0.9Pr0.1CrO3. GzFx order (spin structure of PrCrO3) is dominant after zero field cooling (ZFC), whereas GxFz order (spin structure of YCrO3) is dominant after cooling under a field higher than 100 Oe. Positive/negative exchange bias-like effect, with large vertical shift and small horizontal shift, has been observed after FC/ZFC process. The vertical shift can be attributed to the frozen ordered Pr3+ and Cr3+ spins in magnetic domains, because of the strong coupling between Pr3+ and Cr3+ sublattices; while the horizontal shift is a result of the pinning of spins at the interfaces. The frozen structure is generated by the field used for the measurement of the initial magnetization curve of M(H) for the ZFC cooled sample, while it is generated by the cooling field for the sample cooled under a cooling field higher than 100 Oe.

We report the synthesis of single phase rare earth orthochromite CeCrO3 and its magnetic properties. A canted antiferromagnetic transition with thermal hysteresis at T = 260 K is observed, and a magnetic compensation (zero magnetization) near 133 K is attributed to the antiparallel coupling between Ce3+ and Cr3+ moments. At low temperature, field induced magnetization reversal starting from 43 K for H = 1.2 kOe reveals the spin flip driven by Zeeman energy between the net moments and the applied field. These findings may find potential uses in magnetic switching devices such as nonvolatile magnetic memory which facilitates two distinct states of magnetization.

An enormous spontaneous exchange bias (EB) was obtained after zero-field cooling in Ni50Mn36Co4Sn10 Heusler alloy. It can be attributed to the enhancement of antiferromagnetism, which induces a strong interaction with superferromagnetism, superspin glass, and superparamagnetism. In addition, the EB with an abrupt drop below the lower temperature of 5 K was observed, which can be interpreted as the fact that the rotation of the antiferromagnetic spins from a disordered state to a more ordered state is hindered by domain wall pinning.

We report the magnetic and magnetocaloric properties of Dy1−xHoxMnO3 (0 ≤ x ≤ 1). Large entropy change of 12.5 J/kg K and refrigeration capacity of 312 J/kg at 7 T for HoMnO3 is calculated based on isothermal magnetization measurements. The peak temperature of magnetic entropy change for all samples keeps the same 10.5 K, indicating that Ho3+ doping only affects the value of magnetic entropy. An unambiguous intrinsic structural transition near 7 K is first observed by strain measurement, which is believed as the origin of magnetic symmetry transition of Dy1−xHoxMnO3 and induces the magnetocaloric effect with the cooperation interaction between Dy3+/Ho3+and Mn3+ spins.

The authors report on ductile ultrafine-grained (Ti0.72Fe0.28)100−xTax (0⩽x⩽4) alloys with not only high fracture strength but simultaneously high yield strength exceeding 2000MPa along with distinct plasticity, which are superior to high-strength Ti-based bulk metallic glasses and bimodal composites. All alloys mainly consist of β-Ti and FeTi solid solutions but display different microstructures. The alloys exhibit a high fracture strength >2500MPa and a high yield strength >2000MPa as well as large plasticity of ∼5%–7.5%. The microstructure-property correlation of these ultrafine-grained alloys is discussed.

The nonlinear optical crystal Ba2TiSi2O8 is induced three-dimensionally inside a glass by a femtosecond pulse laser with 800nm, 250kHz, and 150fs. Micro-Raman and photoluminescence spectra confirm that crystals can grow in the focal point of the laser beam. Continuous crystalline lines were written through moving the focal point of the laser beam inside the glass. The results demonstrate a convenient method to engrave three-dimensional patterns of crystals with nonlinear optical properties for integrated optical devices.