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Emergent exotic phenomena in the self-assembled process of vertically aligned nanocomposite (VAN) thin film remain under intensive studies. Insight exploration on the self-assembled formation from the combination of two different phases of materials is not only important to optimize the physical properties yields from those combined materials, but also open up a new avenue to discover new materials with the VAN system. In this work, the thermodynamic control of the self-assembled formation of BiFeO3-CoFe2O4 (BFO-CFO) VAN thin film has been confirmed by studying the effects of substrate temperature during the growth process by pulsed laser deposition (PLD) technique. The structural examination results on the samples, which were growing with various substrate temperatures highlight the importance of the thermodynamic factor to control the crystalline structure of BFO phase and CFO pillar size, which then affect the physical properties and further its practical applications. For instance, we can control the size of the CFO pillar using a temperature substrate to find appropriate spin magnetic switching in the CFO pillar for memory device applications. This study also sheds light on the relationship between thermodynamics and elastic strain energy on the formation of self-assembled matrix-pillars of the BFO-CFO VAN which is important for device fabrication. [ABSTRACT FROM AUTHOR]

The rich physical properties unveiled in a plethora of transition and rare-earth metal oxides have been attributed to the intricate interplays between the orbital, charge, and spin degrees of freedom. Among them, rare-earth manganites (RMnO3) have been attracting tremendous attention owing to the ionic size-induced lattice distortion dictated by the Goldschmidt tolerance factor and the substantial Jahn–Teller distortion unique to Mn3+ ions, which evidently have resulted in a variety of emergent characteristics in electronic, magnetic, and orbital ordering. In this work, we deliberately engineered the orientation of a series of orthorhombic YMnO3 (o-YMO) films grown on SrTiO3(100) [STO(100)] and SrTiO3(110) [STO(110)] substrates by means of pulsed laser deposition. The x-ray diffraction (XRD) and reciprocal space mapping revealed that o-YMO/STO(100) is c-axis-oriented and o-YMO/STO(110) is a-axis-oriented, respectively. The XRD ϕ-scans further indicate that both films have excellent in-plane crystallinity, allowing the exploration of anisotropies along the respective crystallographic orientations. Indeed, the x-ray absorption linear dichroism spectroscopy taken along the respective crystallographic orientations evidently exhibited substantial anisotropy. Theoretical fitting with configuration interaction cluster calculations suggests that the d 3 z 2 − r 2 orbitals are parallel to YMO[001]/(100), leading to stronger electron scattering along the c-axis. Independent polarization-dependent Δ R/R spectra obtained using the femtosecond pump–probe method exhibited substantial anisotropic behaviors in carrier relaxation dynamics when probing along different crystallographic orientations, presumably due to orbital ordering anisotropies. [ABSTRACT FROM AUTHOR]

Hydrogen peroxide (H2O2) production by the electrochemical 2‐electron oxygen reduction reaction (2e− ORR) is a promising alternative to the energy‐intensive anthraquinone process, and single‐atom electrocatalysts show the unique capability of high selectivity toward 2e− ORR against the 4e− one. The extremely low surface density of the single‐atom sites and the inflexibility in manipulating their geometric/electronic configurations, however, compromise the H2O2 yield and impede further performance enhancement. Herein, we construct a family of multiatom catalysts (MACs), on which two or three single atoms are closely coordinated to form high‐density active sites that are versatile in their atomic configurations for optimal adsorption of essential *OOH species. Among them, the Cox–Ni MAC presents excellent electrocatalytic performance for 2e− ORR, in terms of its exceptionally high H2O2 yield in acidic electrolytes (28.96 mol L−1 gcat.−1 h−1) and high selectivity under acidic to neutral conditions in a wide potential region (>80%, 0–0.7 V). Operando X‐ray absorption and density functional theory analyses jointly unveil its unique trimetallic Co2NiN8 configuration, which efficiently induces an appropriate Ni–d orbital filling and modulates the *OOH adsorption, together boosting the electrocatalytic 2e− ORR capability. This work thus provides a new MAC strategy for tuning the geometric/electronic structure of active sites for 2e− ORR and other potential electrochemical processes. [ABSTRACT FROM AUTHOR]

In this study, samarium (Sm-10at%)-doped BiFeO3 (SmBFO) thin films were grown on platinum-coated glass substrates using pulsed laser deposition (PLD) to unveil the correlation between the microstructures and nanomechanical properties of the films. The PLD-derived SmBFO thin films were prepared under various oxygen partial pressures (PO2) of 10, 30, and 50 mTorr at a substrate temperature of 600 °C. The scanning electron microscopy analyses revealed a surface morphology consisting of densely packed grains, although the size distribution varied with the PO2. X-ray diffraction results indicate that all SmBFO thin films are textured and preferentially oriented along the (110) crystallographic orientation. The crystallite sizes of the obtained SmBFO thin films calculated from the Scherrer and (Williamson–Hall) equations increased from 20 (33) nm to 25 (52) nm with increasing PO2. In addition, the nanomechanical properties (the hardness and Young's modulus) of the SmBFO thin films were measured by using nanoindentation. The relationship between the hardness and crystalline size of SmBFO thin films appears to closely follow the Hall–Petch equation. In addition, the PO2 dependence of the film microstructure, the crystallite size, the hardness, and Young's modulus of SmBFO thin films are discussed. [ABSTRACT FROM AUTHOR]

The search for materials for next-generation spintronic applications has witnessed exponentially increasing interest, mainly due to the explosive development of numerous two-dimensional (2D) materials discovered in the last decade. Among them, MXenes have emerged as promising candidates for many applications due to their unique and versatile tunability in structure and properties. In particular, their excellent combination of conductivity and highly charged surfaces leads to outstanding electrochemical properties that are significant in electronic applications. Moreover, the ease of modifying the atomic and electronic structures, and thus the functionalities of MXenes, further opens up the opportunity to realize MXenes-based spintronic device applications. The explosive development of MXenes, such as tuning the bandgap and enhancing their magnetic properties, could pave the way for the integration of MXenes in device configurations suitable for spintronics. In this article, we provide an overview of the potential applications of MXenes with a special focus on spintronic device applications. We commence the discussion with various fundamental aspects of spintronics, including the understanding of materials for spintronics in general, MXenes, and their fabrication, followed by presenting perspectives on plausible strategies and future challenges in integrating MXenes into spintronic devices. [ABSTRACT FROM AUTHOR]