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In this letter, microstructural and mechanical inhomogeneities, a great concern for single crystal Ni-based superalloys repaired by laser assisted 3D printing, have been probed near the epitaxial interface. Nanoindentation tests show the hardness to be uniformly lower in the bulk of the substrate and constantly higher in the epitaxial cladding layer. A gradient of hardness through the heat affected zone is also observed, resulting from an increase in dislocation density, as indicated by the broadening of the synchrotron X-ray Laue microdiffraction reflections. The hardening mechanism of the cladding region, on the other hand, is shown to originate not only from high dislocation density but also and more importantly from the fine γ/γ′ microstructure.

Quasi-one-dimensional (quasi-1D) TaSe3 is attracting considerable attention due to its intriguing superconductivity and possible interplay with nontrivial topology and the charge density wave (CDW) state. However, unlike the isostructural analogs, CDW has not been observed for TaSe3 despite its quasi-1D character that is supposed to promote Peierls instabilities and CDW. Here, we synthesize TaSe3 mesowires (MWs) using a one-step approach. For the MW of ∼300 nm thickness, a distinct CDW transition occurs at 65 K in the resistivity measurement, which is further evidenced by the Raman characterization and the susceptibility measurement. For comparison, we have also prepared bulk single crystal TaSe3. Although no anomaly appears in the resistivity and magnetoresistance measurements, the carrier type detected by the Hall effect varies from n-type to p-type below 50 K, suggesting a reconstruction of the Fermi surface that could be associated with CDW. The enhancement of CDW in the MWs is attributed to the reduced dimensionality. TaSe3 is demonstrated to be a promising platform to study the correlation and competition of CDW and superconductivity in the quasi-1D systems. [ABSTRACT FROM AUTHOR]

We report here an enhanced magnetoelectric effect in a Y-type hexaferrite Ba0.5Sr1.5Zn2Fe12O22 with Fe3+ ions partially substituted by magnetic Cr3+ ions (i.e., BSZFCO). The direct magnetoelectric effect is persistent up to 250 K, with the maximal susceptibility of ~1309 ps/m at 75 K. More importantly, the pronounced non-zero electric polarization at zero magnetic field and four magnetoelectric states induced by different initial poling fields make it quite unique to serve in a magnetoelectric device. The stability of the direct (inverse) magnetoelectric effect is confirmed by the nonvolatile behavior in response to the cyclically sweeping magnetic (electric) fields. Our studies provide an insight into the nontrivial properties of BSZFCO, which are promising for multiferroic applications. [ABSTRACT FROM AUTHOR]

Sr2IrO4 represents a fascinating system to study comparable electronic correlations and spin-orbit couplings, and recently attracts considerable attention in high-temperature superconductivity. Here, we report on the transport and magnetic properties in gallium-doped Sr2IrO4. A metallic state is discovered when doping x is over 0.1, which could be understood in terms of the quickly decreased energy gap and increased carrier concentration. In addition to the high-temperature magnetic transition (TC>200 K), a low-temperature one (T'C ) is also observed for the x=0.05-0.10 samples. Both of the magnetic states are found to be canted antiferromagnetism. The low-temperature phase is strongly depressed by doping and vanishes when doping is further increased, which is probably stabilized by the long-way exchange interactions of diluted Ir4+ spins via Ir3+ ions. Our studies provide an insight into the electrical and magnetic states tuned by chemical doping in Sr2IrO4, thereby facilitating the seeking of superconductivity in this system. [ABSTRACT FROM AUTHOR]

Unusual magnetic anisotropy of the ferromagnetic shape-memory alloy Ni50Fe23Ga27 has been observed. The anisotropy of the austenite becomes very large, even larger than that of the martensite in ribbon samples. Lowering the temperature from 300 K to 80 K, the saturation field of the austenite is dramatically increased from 200 Oe up to 6 kOe. This high-anisotropy behavior clearly highlights the demagnetization effect of the martensitic transformation. The physical mechanism is attributed to a collective effect coming from the atomic disorder, the premartensitic transformation, and the off-stoichiometric Ga-rich composition of the alloys. [ABSTRACT FROM AUTHOR]

Giant exchange bias with a shift up to 3.86 kOe has been observed in γ-Fe2MnGa alloy in which a ferromagnetic to antiferromagnetic transition takes place at 250 K. The transition can be suppressed to lower temperatures by higher magnetic fields at a shift rate of 10.3 K/kOe. Exchange bias and enhanced coercivity occur simultaneously, revealing an exchange coupling between the coexisting antiferromagnetic and ferromagnetic phases. Meanwhile, the internal exchange coupling inside the antiferromagnetic clusters dynamically ensures their unidirectional anisotropy during their size changing following the external magnetic field. [ABSTRACT FROM AUTHOR]

SnO2 thin films were deposited on quartz substrates by pulsed laser deposition and postannealed at different temperatures in oxygen ambience. X-ray diffraction, Hall measurement, and x-ray photoelectron spectroscopy were employed to investigate the properties of the annealed SnO2 thin films. An anomalous electrical transport behavior as a function of the annealing temperature was observed. Both the growth of the crystal grain and oxygen vacancy density variation in the annealing process have been identified to be responsible for the transition of electrical transport properties. [ABSTRACT FROM AUTHOR]

In order to develop multiferroics with large magnetization and polarization, we have prepared the (1-x)BiFeO3–xDyFeO3 (BF-DF) solid solution and systematically studied its properties. A morphotropic phase transition from rhombohedral perovskite (R3c) to orthorhombic orthoferrite (Pbnm) was found at x around 0.1. The magnetic properties of BiFeO3 were improved by the introduction of Dy3+ on the perovskite A site. Chemically modified Bi0.9Dy0.1Fe1-xTixO3+x/2 ceramics by aliovalent ionic substitution of Ti4+ for Fe3+ with excess Bi2O3 exhibit weak ferromagnetism and a typical ferroelectric hysteresis loop with a large remnant polarization of 23 μC/cm2 at room temperature and a large saturated magnetization (Ms=0.5 μB/f.u.) at 2 K. These properties entitle the BF-DF solid solution one of few multiferroic materials that exhibit both decent magnetization and electric polarization. [ABSTRACT FROM AUTHOR]

In this work, Al2O3 thin film containing Al nanocrystals (nc-Al) is deposited on Si substrate by radio frequency sputtering to form a metal-insulator-semiconductor structure. Both electron and hole trapping in nc-Al are observed. The charge storage ability of the nc-Al/Al2O3 thin films provides the possibility of memory applications. Charging in the nc-Al also leads to a change in the dc resistance of the thin films, namely, the electron trapping in the nc-Al leads to an increase in the resistance, whereas the resistance is reduced if there is hole trapping in the nc-Al. [ABSTRACT FROM AUTHOR]

Ceramics of 0.67Bi(Fe1-xTix)O3+x/2–0.33PbTiO3 (x=0, 0.005, 0.01, 0.02, 0.04) were prepared by solid state reactions, with a relative density of 94%–97%. The dielectric and ferroelectric properties of the ceramics have been significantly improved by means of aliovalent ionic substitution of Ti4+ for Fe3+, which reduces the electric conductivity. The temperature variation of the dielectric constant has been measured up to the Curie temperature as high as TC=650 °C. A saturated dielectric hysteresis loop with a remnant polarization (Pr) of 9 μC/cm2 is displayed in the 0.5 mol % Ti4+-substituted sample at room temperature. Pr reaches 17 μC/cm2 in the sample with 2 mol % Ti4+ even though the hysteresis loop is not saturated, suggesting that a much higher saturated polarization can be expected in the Ti4+-substituted BiFeO3–PbTiO3 ceramics. [ABSTRACT FROM AUTHOR]

The annealing temperature effect on the band structure of Ba0.65Sr0.35TiO3 (BST) thin films coated on n-type Si(100) substrate was investigated by ellipsometry and x-ray photoelectron spectroscopy. The band energy shifts of sol-gel BST films annealed at different temperatures are dependent on their developed microstructure. Related to the amorphous BST films annealed at 600 °C, the polycrystalline BST film annealed at 700 °C exhibits narrow band gap, upwards-moved Fermi level, and downwards-moved conduction band minimum, which are believed to contribute the enhanced field emission of BST-coated Si field emitter arrays. [ABSTRACT FROM AUTHOR]

Single-crystalline Al-doped Ba0.6Sr0.4TiO3 (BST) thin films have been pulsed-laser deposited onto Ir/MgO buffered Si substrates. Spectral-resolved microprobe cathodoluminescence measurements of Al-doped BST thin films at room temperature clearly showed three detectable luminescence bands in the wavelength range between 200 and 900 nm. We assigned the first shoulder peak to saturation of phonon-assisted processes, with a band gap transition resulting in the second sharp band. The band-maximum position of a third (defect-related) broad luminescence band varied with varying the concentration of Al dopant. By fitting this latter band as the sum of three superimposed Gaussian curves, it was revealed that the incorporation of Al dopant into the BST crystal lattice had a direct impact on the defect population existing in the single-crystalline film. For perovskite ABO3-structured BST thin films, it is suggested that the Al dopant occupies the B site (Ti) in a low range of dopant concentrations, while at higher dopant concentrations Al might occupy both A sites (Ba or Sr) and B sites. [ABSTRACT FROM AUTHOR]

Sr2IrO4 represents a fascinating system to study comparable electronic correlations and spin-orbit couplings, and recently attracts considerable attention in high-temperature superconductivity. Here, we report on the transport and magnetic properties in gallium-doped Sr2IrO4. A metallic state is discovered when doping x is over 0.1, which could be understood in terms of the quickly decreased energy gap and increased carrier concentration. In addition to the high-temperature magnetic transition (TC>200 K), a low-temperature one (T'C ) is also observed for the x=0.05-0.10 samples. Both of the magnetic states are found to be canted antiferromagnetism. The low-temperature phase is strongly depressed by doping and vanishes when doping is further increased, which is probably stabilized by the long-way exchange interactions of diluted Ir4+ spins via Ir3+ ions. Our studies provide an insight into the electrical and magnetic states tuned by chemical doping in Sr2IrO4, thereby facilitating the seeking of superconductivity in this system. [ABSTRACT FROM AUTHOR]

With rapid development towards shrinking the size of traditional photonic systems such as cameras, spectrometers, displays and illumination systems, there is an urgent need for high performance and ultra-compact functional optical elements. The large footprint of traditional bulky optical elements, their monofunctional response and the inability for direct integration into nanophotonic devices have severely limited progress in this area. Metasurfaces, consisting of an array of subwavelength nanoscatterers with spatially varying geometries, have shown remarkable performance as ultrathin multifunctional optical elements. Here, based on an all-dielectric metasurface, we propose and experimentally demonstrate a spatial domain optical depolarizer capable of efficiently depolarizing linearly polarized light in the visible spectral band from 450 nm to 670 nm, with a degree of polarization of less than 10 %. Remarkably, it is capable of depolarizing light beam with a diameter down to several micrometers, about two orders of magnitude smaller than commercial liquid crystal depolarizers. Furthermore, the long response time, bulky footprint, tight optical alignment tolerance and large pixel size severely limit the performance and system integration of commercial depolarizers. We envision the metasurface depolarizer to find applications in next generation ultra-compact grating spectrometers and illumination systems.