Giant and isotropic magnetoresistance as huge as −53% was observed in magnetic manganese oxide La0.72Ca0.25MnOz films with an intrinsic antiferromagnetic spin structure. We ascribe this magnetoresistance to spin‐dependent electron scattering due to spin canting of the manganese oxide.

31p-S-4 Giant Magnetoresistance in Magnetic Manganese Oxide with Intrinsic Antiferromagnetic Spin Structure

We demonstrate first room temperature, and ultrabright single photon emission from a color center in two-dimensional multilayer hexagonal boron nitride. Density Functional Theory calculations indicate that vacancy-related centers are a likely source of the emission.

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Quantum emission from hexagonal boron nitride monolayers

Developing thermoelectric materials with superior performance means tailoring interrelated thermoelectric physical parameters – electrical conductivities, Seebeck coefficients, and thermal conductivities – for a crystalline system. High electrical conductivity, low thermal conductivity, and a high Seebeck coefficient are desirable for thermoelectric materials. Therefore, knowledge of the relation between electrical conductivity and thermal conductivity is essential to improve thermoelectric properties. In general, research in recent years has focused on developing thermoelectric structures and materials of high efficiency. The importance of this parameter is universally recognized; it is an established, ubiquitous, routinely used tool for material, device, equipment and process characterization both in the thermoelectric industry and in research. In this paper, basic knowledge of thermoelectric materials and an overview of parameters that affect the figure of merit ZT are provided. The prospects for the optimization of thermoelectric materials and their applications are also discussed.

A review on thermoelectric renewable energy: Principle parameters that affect their performance

Ferromagnetism usually only occurs in materials containing elements that form covalent 3d and 4f bonds. Its occurrence in pure carbon is therefore surprising, even controversial. A systematic magnetic force microscope study indicates that ferromagnetism in graphite is the result of localized spins that arise at grain boundaries.

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Room-temperature ferromagnetism in graphite driven by two-dimensional networks of point defects

An urgent need is to reduce the flammability of polymers and manage their toxic thermal decomposition products. Although conventional halogenated, metallic and phosphorus-based flame retardants (FRs) proved effective, they are known to cause major damage to human health and the environment. Containing carbon nanomaterials as a new class of flame retarding additives, polymer nanocomposites have displayed high flame retardancy, mechanical performance and electrical and thermal conductivity – a feat unmatched by conventional FRs. In this article we review very recent advances in carbon nanomaterials as FRs for polymers and composites as well as new understanding of the underpinning flame retarding mechanisms. Carbon nanomaterials, i.e. graphene, carbon nanotubes and carbon black, are discussed as the alternatives to conventional fillers due to their effectiveness in improving the polymers' flammability, mechanical properties and conductivity. The synergy between carbon-based nanofillers and conventional FRs is comprehensively reviewed, concluding that adding small fractions of carbon nanomaterials with conventional FRs into polymers can not only synergistically improve the flame retardancy but result in multifunctionalities such as thermal and electrical conductivity, without compromising the polymers’ mechanical performance. Chemically or physically combining carbon nanomaterials with other compounds or nanoadditives containing phosphorus and nitorgen elements can create significant synergies for multifunctional polymers and composites to attain superior flame-retardant properties.

Recent advances in carbon-based nanomaterials for flame retardant polymers and composites

Herein, high-density La0.7(Ca0.205Sr0.095)MnO3:xAg2O composites (LCSMO:xA, 0.0 ≤ x ≤ 0.5) are successfully fabricated by using a combination of sol–gel and solid-state methods. The electromagnetic properties are investigated using a phenomenological percolation (PP) model, double exchange (DE) mechanism and Jahn–Teller (JT) effect. Moreover, X-ray diffraction (XRD) and scanning electron microscopy (SEM) are employed to analyze the crystal structure and morphology of LCSMO:xA composites. The distortion of MnO6 octahedron is confirmed via Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy. Also, the valence states and ionic stoichiometry are assessed by using X-ray photoemission spectroscopy (XPS). The results reveal that Ag+ ions, occupying the A-sites, significantly influence the crystal structure, formation of Mn3+/Mn4+ pairs, and distortion of MnO6 octahedron. Furthermore, the presence of metallic Ag at grain boundaries (GBs) improves the conductivity of LCSMO:xA composites by providing the desired conductive channels. At the Ag2O content of x = 0.2, the maximum temperature coefficient of resistance (TCR) of the resistivity is found to be 17.26% K−1 at 299.9 K, whereas the low-field magnetoresistance (MR, 0.8 T magnetic field) is found to be 30.34% at 300.93 K. This room-temperature TCR value is the highest among those for the studied perovskite-structured manganese oxide composites. These results confirm that the room-temperature TCR and MR values of LCSMO:xA composites can be tuned by optimizing the content of metallic Ag and Ag+ ions.

Hui Zhang

Papers

Utilization of metallic Ag and Ag+ ions to optimize room-temperature TCR and MR of La0.7(Ca0.205Sr0.095)MnO3:xAg2O composites

Silver addition in polycrystalline La0.7Ca0.3MnO3: Large magnetoresistance and anisotropic magnetoresistance for manganite sensors

Effects of annealing atmosphere on thermoelectric signals from ZnO films

Tuning the Electronic Properties of Atomically Precise Graphene Nanoribbons by Bottom-Up Fabrication

La1−xCaxMnO3:Ag0.2 (0.25 ≤ x ≤ 0.31) ceramics with high temperature coefficient of resistivity under magnetic field