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Ferrimagnets with magnetic compensation temperature ( Tcomp) around room temperature are desirable due to their potential applications in low-energy consuming and high-frequency spintronic devices. In this study, the Tcomp of ferrimagnetic Mn2.21Ru0.86Ga (MRG) is tuned to near room temperature by strain. Moreover, we observed unconventional magnetoresistance behaviors for MRG-based Hall bar devices near Tcomp. First-principles calculations suggest two kinds of Mn moments, which lead to two anomalous Hall channels with opposite signs and consequently correspond to the peak structure and triple loops of the anomalous Hall effect loops. The unconventional temperature dependence of longitudinal resistivity is caused by the combined effects of two types of Mn moments and the anisotropic magnetoresistance of the MRG film. Interestingly, the spontaneous Hall angle of the MRG film is calculated to be ∼2.2%, which is one order of magnitude larger than those of other 3 d ferromagnets. Therefore, our study demonstrates MRG to be a ferrimagnet with the Tcomp near room temperature, which enables its potential applications in spintronic devices.

The heart of current high-throughput computational design for two-dimensional (2D) van der Waals (vdW) functional heterostructures is Anderson's rule (AR). This non-interacting model, however, inevitably introduces error and uncertainty in design results, problems which remain neglected. We report that, even for a non-magnetic system, the current high-throughput design framework commonly omits potential candidates in specific fields, such as heterostructure solar cell research. Therefore, this framework is fragile to extend to all subfields of functional vdW heterostructures. Through the analysis of several factors, such fragility is found to arise mainly from interlayer orbital coupling. This effect is omitted by AR and causes statistical deviation in the prediction of electronic properties. In the absence of a more advanced and universal physical model for describing interlayer orbital coupling, we propose a robust high-throughput design framework to reduce the omission of potential candidates. This work deepens the understanding of high-throughput design for 2D vdW functional heterostructures and provides insight into their development.

The size effect on the structural and optical properties of cubic Er2O3 was investigated under pressure by in-situ angular dispersive synchrotron x-ray diffraction (AD-XRD), Raman scattering, photo...

In this study, the electrocaloric effect (ECE) of Bi0.5Na0.5TiO3–0.06BaTiO3 (BNT–0.06BT) ceramic has been directly measured using a home-made adiabatic calorimeter. The maximum adiabatic temperature change (ΔT) approaches 0.86 K under an electric field of 5 kV/mm at 110 °C, which provides experimental evidence for optimizing the ECE near the type–I pseudo–first–order phase transition (PFOPT). Most importantly, a considerable ΔT value can be maintained over a wide temperature range well above the temperature of the PFOPT under a high electric field. In addition, ΔT is closely related to the structural transition and electric field strength. This work provides a guideline to investigate the high ECE in BNT–based ferroelectric ceramics for applications in cooling technologies.

Rare earth phosphors have been widely studied because of their sharp emission lines and excellent optical performance. However, photoluminescence (PL) tuning by crystal field in Er3+ embedded phosphors has always been a challenge. Here, we demonstrate that pressure can help to enhance the red and green light emission simultaneously in Er:GdVO4. Synchrotron X-ray diffraction investigations revealed that a structural phase transition was responsible for the enhancement. Our work brightens the future prospects for applications of Er3+-based PL materials in various fields, such as high power lasers and (bio) medical imaging.

A beam of light that is incoherent to the recording beams and has its polarization orthogonal to the recording beams is shown to assist the recording process of azo-functionalized polymers through the enhancement of trans–cis–trans cycling. Recording with s:s polarization has earlier been shown to result in very small surface modulations. However, with the help of an incoherent assisting beam, it can record a large surface modulation with a diffraction efficiency of 20.7%. The incoherent assisting beam also leads to an acceleration of the grating formation rate for the recording beams with p:p and 45°:45° polarization.

Electroabsorption spectroscopy measurements are reported on a multilayer thin film of a prototypical azopolymer. The sample was prepared by sequentially dipping the substrate into aqueous solutions containing the polycation poly(diallyl dimethyl ammonium chloride) and the polyanion CH-1A-NS, an epoxy based polymer with azobenzene chromophore. The measured ratio of χ3333(3) to χ1133(3) for the electrostatically assembled film is 4, which indicates that the chromophores in this film are oriented preferentially perpendicular to the film plane instead of an isotropic distribution in three-dimensional space. For comparison, a spin coated film of CH-1A-NS was studied by the same method. The ratio of χ3333(3) to χ1133(3) for the spin coated film is found to be 1.9, indicating that the same chromophores in the spin coated film are oriented preferentially in the film plane. These results imply that the process of electrostatic layer-by-layer adsorption leads to a preferred orientation of the chromophores, perpendi...

The Raman signature of the local Ge–C mode for substitutional C is identified as a narrow line (8 cm−1 full width at half maximum) near 530 cm−1 in alloy films of Ge1−yCy (0⩽y⩽0.07) grown on Ge (100) substrates by low-temperature (200 °C) molecular beam epitaxy. The intensity of the Ge–C line relative to the c-Ge line suggests that only a small fraction of the nominal C is in substitutional sites. In ternary alloys of Ge1−x−ySixCy with x=0.1 and 0.2 and y=0.03, the Ge–C mode disappears, suggesting a strong bias towards C bonding with Si as opposed to Ge. In Ge1−xSnx films the Ge–Sn mode is seen at 263 cm−1.

Thermal decomposition of an amido precursor; [Ga2(NMe2)6, Me=CH3] in an ammonia atmosphere yielded nanostructured gallium nitride powder. The x-ray diffraction spectrum of the nanosized gallium nitride exhibited reflections corresponding to the lattice planes of fcc (zinc blende) GaN. High resolution transmission electron microscopy confirmed the cubic structure of the material and evidence of stacking faults within the fcc structure. Infrared spectra showed the characteristic Ga–N stretch at 550 cm−1. Transmission electron microscope measurements indicated that the GaN consisted of ≈50 nm sized particles which in turn are agglomerates of smaller particles with ≈5 nm domain sizes. The photoluminescence (PL) emission spectrum of the GaN was found to be sensitive to the excitation wavelength exhibiting peaks at 378 and 317 nm. The PL excitation spectrum showed resonances in the 200–300 nm region. These PL results suggest the effect of quantum confinement in these GaN particles.

We developed a dual frequency cholesteric light shutter which utilizes a cholesteric liquid crystal; the dielectric anisotropy of the material changes from positive to negative when the frequency of applied voltage is increased. The shutters are switched to the transparent homeotropic texture by low frequency voltages, and switched to the reflecting planar texture by high frequency voltages. We designed a waveform which reduced the transition time from the homeotropic texture to the planar texture to less than 100 ms.

We report on the molecular beam epitaxial growth of Ge on Si(110) surfaces. High temperature cleaning (oxide desorption) results in the formation of shallow faceted pits distributed randomly on the Si(110) surface. Deposition of Ge at temperatures between 600 and 725 °C leads to preferential nucleation along the pit edges forming elongated islands, which subsequently grow to compact three-dimensional coherent islands. The observation of strained islands in close proximity to each other offers insights into their nucleation behavior and strain relaxation. Our observations suggest heterogeneous nucleation as a possible method for fabricating assemblies of quantum dots.

We report on the microstructural development and optical properties of epitaxial Ge1−xCx alloys (0

Transient dielectric measurement is used to study the transitions among the planar, focal conic, and homeotropic states of cholesteric liquid crystals. If the initial state is the field‐induced homeotropic state, at low bias fields, the liquid crystal transforms to the planar state in a sequence of homeotropic‐transient planar–planar; at high bias fields, the liquid crystal transforms to the focal conic state. The homeotropic‐transient planar transition is on the order of 1 ms while the homeotropic‐focal conic transition is on the order of 100 ms. Large hysteresis is observed in the transitions between the homeotropic and the focal conic state. Based on the rapid homeotropic‐transient planar transition and the hysteresis effect in the focal conic‐homeotropic transition, we have designed a drive scheme which can address bistable reflective cholesteric displays at the speed of one line per millisecond.

We studied the electro‐optical response of a bistable cholesteric texture (BCT) display to ac voltage pulses. The material can be driven into states where planar and focal conic textures coexist at zero field and gray scale memory is achieved. According to the properties of the BCT display we designed two drive schemes; one for binary operation and the other for gray scale operation. We made a 320×320 pixel reflective display with a resolution of 80 lines/in. on a passive matrix. Measurement in an integration chamber showed that the display has higher contrast and better viewing angle than a reflective super twisted nematic display.

A new dispersion involving a polymer in low concentration with a cholesteric liquid crystal is reported. Two types of light modulators from these materials are described as a normal mode shutter which is opaque (light scattering) in the field‐OFF state and transparent in the field‐ON state and a reverse‐mode shutter with the opposite field conditions. The transparent state of both cells is haze‐free for all viewing angles making the material attractive for window applications and direct view displays.

The electro-optic Kerr effect with a high Kerr constant around 10−9 m/V2 was observed in the polymer-stabilized isotropic liquid crystals over a wide temperature range. Optical isotropy at the field-off state was attained with randomly oriented domains of (chiral) nematic liquid crystals formed by a polymer matrix cured in the isotropic phase. Optical birefringence in the field-on state was induced by the reorientation of liquid crystals in the domains. Rapid rising and falling response times of the cells around 0.26 ms (0.52 ms total response time) were achieved. A theoretical model was proposed to explain the experimental results and agreed well with the results.

Ti-22.4Nb-0.73Ta-2.0Zr-1.34O (at. %) alloy after cold compression to similar to 5.2% strain was investigated. The alloy exhibited multiple plastic deformation mechanisms, including the stress-induced alpha(') martensitic (SIM alpha(')) and omega phase transformations, 1/2 dislocations slipping on the {112}beta planes as well as {332} beta and {112} beta twinning, which have not previously been reported to coexist in a titanium alloy. It was also found that beta phase with the {200} planes vertical to the compression direction was almost completely consumed away by a beta -> SIM alpha(') transformation, and a (100) texture of SIM alpha(') formed.

We investigated the electronic states in amorphous In–Ga–Zn–O films with high carrier concentrations by optical absorption and hard x-ray photoelectron spectroscopy (HX-PES). Films having different Hall mobilities were prepared and their annealing effects were examined. All HX-PES spectra showed Fermi edge structures and extra subgap densities of states (DOSs). Tail-like structures observed in the optical spectra originate from subgap DOSs (⪢1020cm−3) near valence band maximas (VBMs). Subgap DOSs near VBMs provide a reason why In–Ga–Zn–O thin film transistors show hard saturation in off states and are difficult to operate in an inversion p-channel mode.

The ab initio calculation and bond valence model (BVM) are employed to investigate dopant occupancy in the Ti-doped high-temperature phase Ta2O5. In this structure, there are two types of Ta atoms, which the authors denote as Ta1 locating inside oxygen octahedral and Ta2 locating inside oxygen decahedral. The 5d state electron configuration of Ta1 and Ta2 is different, the hybridization between Ta1 5d state and O 2p state is stronger than that between Ta2 and O. The chemical bonding between Ta and oxygen ions is mainly covalent. However, there is an increase of the covalent character in going from Ta1–O bond to Ta2–O bond. Both total energy method and BVM indicate that Ti substituting Ta1 is energy favorable, and this maybe due to different electronic structures of Ta1 and Ta2.