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Multiferroic tunnel junctions (MFTJs) have aroused significant interest due to their functional properties useful for nonvolatile memory devices. So far, however, all of the existing MFTJs have been based on perovskite-oxide heterostructures limited by a relatively high resistance-area (RA) product unfavorable for practical applications. Here, using first-principles calculations, we explore spin-dependent transport properties of van der Waals (vdW) MFTJs which consist of two-dimensional (2D) ferromagnetic FenGeTe2(n= 3, 4, 5) electrodes and 2D ferroelectric In2Se3barrier layers. We demonstrate that such FemGeTe2/In2Se3/FenGeTe2(m, n= 3, 4, 5; m≠ n) MFTJs exhibit multiple nonvolatile resistance states associated with different polarization orientation of the ferroelectric In2Se3layer and magnetization alignment of the two ferromagnetic FenGeTe2layers. We find a remarkably low RA product (less than 1 Ω·μm2) which makes the proposed vdW MFTJs superior to the conventional MFTJs in terms of their promise for nonvolatile memory applications.

Fe undergoes a corrosion process under aerobic conditions. Oxidized forms of Fe lose malleability, durability, and other critical physical properties. For spintronic applications, alloy forms or capping layers are used to modulate the properties of Fe. Observing the Fe(111) spin structure is critical for practical applications. We suggest a method of coating Fe to retain its original magnetic properties. Thanks to monolayer graphene (MLG) growth, the properties of the Fe spin structure do not change, even under ambient conditions. Through angle-resolved photoemission spectroscopy (ARPES) and low-energy electron diffraction (LEED) measurements, we also found that interfacial band structures are modulated due to the presence of MLG.

van der Waals (vdW) heterostructures, stacking different two-dimensional materials, have opened up unprecedented opportunities to explore new physics and device concepts. Especially interesting are recently discovered two-dimensional magnetic vdW materials, providing new paradigms for spintronic applications. Here, using density functional theory (DFT) calculations, we investigate the spin-dependent electronic transport across vdW magnetic tunnel junctions (MTJs) composed of Fe3GeTe2ferromagnetic electrodes and a graphene or hexagonal boron nitride (h-BN) spacer layer. For both types of junctions, we find that the junction resistance changes by thousands of percent when the magnetization of the electrodes is switched from parallel to antiparallel. Such a giant tunneling magnetoresistance (TMR) effect is driven by dissimilar electronic structure of the two spin-conducting channels in Fe3GeTe2, resulting in a mismatch between the incoming and outgoing Bloch states in the electrodes and thus suppressed transmission for an antiparallel-aligned MTJ. The vdW bonding between electrodes and a spacer layer makes this result virtually independent of the type of the spacer layer, making the predicted giant TMR effect robust with respect to strain, interface distance, and other parameters, which may vary in the experiment. We hope that our results will further stimulate experimental studies of vdW MTJs and pave the way for their applications in spintronics.

This research explores the studies published in English from 2004 to 2013 on the Public Speaking (PS) course to provide a preliminary framework of the research paradigm and identify its major themes and sub-themes in this field. A majority of the studies were from the communication literature, with the remaining studies coming from the disciplines of linguistics, education and psychology, which indicates research on PS is multidisciplinary. In the literature, the years 2004 and 2005 saw a peak of studies from native-speaking countries while the years 2011 and 2012 began to see an increase of the research from non-native speaking countries. Nearly half of the studies fell into the non-empirical category. With the method of content analysis and based on the research agenda in the public speaking proposed by Lucas (2011), seven themes were identified, including public speaking anxiety, goals of the public speaking course and pedagogical strategies, pedagogical content, course assessment, technology and integrative methods as pedagogy, PS textbooks, and adaptation of the course to non-native speakers. It is hoped that the findings here can contribute to refining research on PS course in China and providing insights for Chinese practitioners.

Photocatalysis technology, using semiconductor nano-materials to decompose toxic pollutants under solar light irradiation, displays great prospects for environmental protection. This review gives an overview of the applications of BiOX (X = Cl, Br and I) photocatalysts for efficient photocatalytic degradation (PCD) removal of pollutants in water/air, such as volatile organic compounds (VOCs), organic molecule pollutants, polymer pollutants and biological substances. In addition, the hybridization, facet effects and photocatalytic mechanisms of BiOX are highlighted to offer guidelines for designing highly-active BiOX visible-light-driven (VLD) photocatalysts. Furthermore, the research trends and future prospects of BiOX photocatalysts are also briefly summarized. It may lead to feasible green and efficient photocatalytic reaction systems using BiOX as the photocatalyst.