Correlation between epitaxial strain and magnetic properties in La0.7Sr0.3CoO3/La0.7Sr0.3MnO3 bilayers

Magnetic properties arising at interfaces of perovskite oxides such as La 0.7 Sr 0.3 CoO 3 (LSCO) and La 0.7 Sr 0.3 MnO 3 (LSMO) depend sensitively on the fine details of their structural properties. In this work, we use high-resolution transmission electron microscopy and spectroscopy to examine the structural and electronic phenomena at the interfaces in two LSCO/LSMO bilayers with reversed growth order. Two different strain mechanisms are at work in these films: compressive or tensile epitaxial strain, and distortion of the octahedral tilt pattern to maintain a network of corner-sharing octahedra. While the epitaxial strain is constant regardless of the growth order, the modification of the octahedral tilt pattern depends on whether the film is grown directly on the substrate or as the second sublayer. As a consequence, exchange spring behavior is observed only when the LSCO sublayer is grown first. The different mechanisms of strain accommodation within the oxygen octahedra network in each material proved to be of critical importance in determining the interfacial structure and thus magnetic and electronic properties of the bilayers

Tuning interfacial exchange interactions via electronic reconstruction in transition-metal oxide heterostructures

The impact of interfacial electronic reconstruction on the magnetic characteristics of La0.7Sr0.3CoO3 (LSCO)/La0.7Sr0.3MnO3 (LSMO) heterostructures was investigated as a function of layer thickness using a combination of soft x-ray magnetic spectroscopy and bulk magnetometry. We found that the magnetic properties of the LSCO layers are impacted by two competing electronic interactions occurring at the LSCO/substrate and LSMO/LSCO interfaces. For thin LSCO layers (<5 nm), the heterostructures exist in a highly coupled state where the chemically distinct layers behave as a single magnetic compound with magnetically active Co2+ ions. As the LSCO thickness increases, a high coercivity LSCO layer develops which biases a low coercivity layer, which is composed not only of the LSMO layer but also an interfacial LSCO layer. These results suggest an intriguing route to tune the magnetic properties of transition metal oxide heterostructures through careful control of the interface structure

Enabling Overall Water Splitting on Photocatalysts by CO-Covered Noble Metal Co-catalysts

Photocatalytic overall water splitting requires co-catalysts that efficiently promote the generation of H₂ but do not catalyze its reverse oxidation. We demonstrate that CO chemisorbed on metal co-catalysts (Rh, Pt, Pd) suppresses the back reaction while maintaining the rate of H₂ evolution. On Rh/GaN:ZnO, the highest H₂ production rates were obtained with 4–40 mbar of CO, the back reaction remaining suppressed below 7 mbar of O₂. The O₂ and H₂ evolution rates compete with CO oxidation and the back reaction. The rates of all reactions increased with increasing photon absorption. However, due to different dependencies on the rate of charge carrier generation, the selectivities for O₂ and H₂ formation increased in comparison to CO oxidation and the back reaction with increasing photon flux and/or quantum efficiency. Under optimum conditions, the impact of CO to prevent the back reaction is identical to that of a Cr₂O₃ layer covering the active metal particle

Identifying correlates of suicide ideation during the COVID-19 pandemic: A cross-sectional analysis of 148 sociodemographic and pandemic-specific factors.

The coronavirus disease 2019 (COVID-19) pandemic has created a global health crisis, with disproportionate effects on vulnerable sociodemographic groups. Although the pandemic is showing potential to increase suicide ideation (SI), we know little about which sociodemographic characteristics or COVID-19 experiences are associated with SI. Our United States-based sample (n = 837 adults [mean age = 37.1 years]) completed an online survey during August-September 2020. The study utilized an online convenience sample from a prior study, which was enriched for exposure to trauma and experiences of posttraumatic stress symptoms. We assessed SI using the Beck Depression Inventory-II. Traditional (i.e., logistic regression) and machine learning (i.e., LASSO, random forest) methods evaluated associations of 148 self-reported COVID-19 factors and sociodemographic characteristics with current SI. 234 participants (28.0%) reported SI. Twenty items were significantly associated with SI from logistic regression. Of these 20 items, LASSO identified seven sociodemographic characteristics (younger age, lower income, single relationship status, sexual orientation other than heterosexual as well as specifically identifying as bisexual, non-full-time employment, and living in a town) and six COVID-19 factors (not engaging in protective COVID-19 behaviors, receiving mental health treatment (medication and/or psychotherapy) due to the COVID-19 pandemic, socializing during the pandemic, losing one's job due to COVID-19, having a friend with COVID-19, and having an acquaintance with COVID-19) associated with SI. Random forest findings were largely consistent with LASSO. These findings may inform multidisciplinary research and intervention work focused on understanding and preventing adverse mental health outcomes such as SI during and in the aftermath of the pandemic