Anisotropic Galvanomagnetic Effects in Single Cubic Crystals: A Theory and Its Verification.

A theory of anisotropic galvanomagnetic effects in single cubic crystals and its experimental verifications are presented for the current in the (001) plane. In contrast to the general belief that galvanomagnetic effects in single crystals are highly sensitive to many internal and external effects and have no universal features, the theory predicts universal angular dependencies of longitudinal and transverse resistivity and various characteristics when magnetization rotates in the (001) plane, the plane perpendicular to the current, and the plane containing the current and [001] direction. The universal angular dependencies are verified by experiments on Fe_{30}Co_{70} single cubic crystal film. The findings provide new avenues for fundamental research and applications of galvanomagnetic effects, because single crystals offer advantages over polycrystalline materials for band structure and crystallographic orientation engineering.

Critical behaviors of van der Waals itinerant ferromagnet Fe3.8GaTe2.

The critical behavior of the van der Waals ferromagnet Fe3.8GaTe2was systematically studied through measurements of isothermal magnetization, with the magnetic field applied along thec-axis. Fe3.8GaTe2undergoes a non-continuous paramagnetic to ferromagnetic phase transition at the Curie temperatureTc∼ 355 K. A comprehensive analysis of isotherms aroundTcutilizing the modified Arrott diagram, the Kouvel-Fisher method, the Widom scaling law, and the critical isotherm analysis yielded the critical exponent ofß= 0.411,γ= 1.246, andδ= 3.99. These critical exponents are found to be self-consistent and align well with the scaling equation at high magnetic fields, underscoring the reliability and intrinsic nature of these parameters. However, the low-field data deviates from the scaling relation, exhibiting a vertical trend whenT

Incommensurate Spin Density Wave in Antiferromagnetic RuO_{2} Evinced by Abnormal Spin Splitting Torque.

Since the discovery of antiferromagnetism, metallic oxide RuO_{2} has exhibited numerous intriguing spintronics properties such as the anomalous Hall effect and anisotropic spin splitting effect. However, the microscopic origin of its antiferromagnetism remains unclear. By investigating the spin splitting torque in RuO_{2}/Py, we found that metallic RuO_{2} exhibits a spatially periodic spin structure which interacts with the spin waves in Py through interfacial exchange coupling. The wavelength of such structure is evaluated within 14-20 nm depending on the temperature, which is evidence of an incommensurate spin density wave state in RuO_{2}. Our work not only provides a dynamics approach to characterize the antiferromagnetic ordering in RuO_{2}, but also offers fundamental insights into the spin current generation due to anisotropic spin splitting effect associated with spin density wave.

Acoustic spin rotation in heavy-metal-ferromagnet bilayers.

Through pumping a spin current from ferromagnet into heavy metal (HM) via magnetization precession, parts of the injected spins are in-plane rotated by the lattice vibration, namely acoustic spin rotation (ASR), which manifests itself as an inverse spin Hall voltage in HM with an additional 90° difference in angular dependency. When reversing the stacking order of bilayer with a counter-propagating spin current or using HMs with an opposite spin Hall angle, such ASR voltage shows the same sign, strongly suggesting that ASR changes the rotation direction due to interface spin-orbit interaction. With the drift-diffusion model of spin transport, we quantify the efficiency of ASR up to 30%. The finding of ASR endows the acoustic device with an ability to manipulate spin, and further reveals a new spin-orbit coupling between spin current and lattice vibration.

Intrinsic Ferromagnetic Semiconductors with High Saturation Magnetization from Hybrid Perovskites.

Ferromagnetic semiconductors (FMS) enable simultaneous control of both charge and spin transport of charge carriers, and they have emerged as a class of highly desirable but rare materials for applications in spin field-effect transistors and quantum computing. Organic-inorganic hybrid perovskites with high compositional adjustability and structural versatility can offer unique benefits in the design of FMS but has not been fully explored. Here, a series of molecular FMSs based on the 2D organic-inorganic hybrid perovskite structure, namely (2ampy)CuCl4 , (3ampy)CuCl4 , and (4ampy)CuCl4 , is demonstrated, which exhibits high saturation magnetization, dramatic temperature-dependent conductivity change, and tunable ferromagnetic resonance. Magnetic measurements reveal a high saturation magnetization up to 18.56 emu g-1 for (4ampy)CuCl4 , which is one of the highest value among reported hybrid FMSs to date. Conductivity studies of the three FMSs demonstrate that the smaller adjacent octahedron distance in the 2D layer results in higher conductivity. Systematic ferromagnetic resonance investigation shows that the gyromagnetic ratio and Landau factor values are strongly dependent on the types of organic cations used. This work demonstrates that 2D hybrid perovskite materials can simultaneously possess both tunable long-range ferromagnetic ordering and semiconductivity, providing a straightforward strategy for designing and synthesizing high-performance intrinsic FMSs.

Surface coupling in Bi2Se3 ultrathin films by screened Coulomb interaction.

Single-particle band theory has been very successful in describing the band structure of topological insulators. However, with decreasing thickness of topological insulator thin films, single-particle band theory is insufficient to explain their band structures and transport properties due to the existence of top and bottom surface-state coupling. Here, we reconstruct this coupling with an equivalently screened Coulomb interaction in Bi2Se3 ultrathin films. The thickness-dependent position of the Dirac point and the magnitude of the mass gap are discussed in terms of the Hartree approximation and the self-consistent gap equation. We find that for thicknesses below 6 quintuple layers, the magnitude of the mass gap is in good agreement with the experimental results. Our work provides a more accurate means of describing and predicting the behaviour of quasi-particles in ultrathin topological insulator films and stacked topological systems.

Significant Change of Metal Cations in Geometric Sites by Magnetic-Field Annealing FeCo2 O4 for Enhanced Oxygen Catalytic Activity.

The application of magnetic fields in the oxygen reduction/evolution reaction (ORR/OER) testing for electrocatalysts has attracted increasing interest, but it is difficult to characterize on-site surface reconstruction. Here, a strategy is developed for annealing-treated FeCo2 O4 nanofibers at a magnetic field of 2500 Oe, named FeCo2 O4 -M, showing a right-shifted half-wave potential of 20 mV for the ORR and a left-shifted overpotential of 60 mV at 10 mV cm-2 for the OER as compared with its counterpart. Magnetic characterizations indicate that FeCo2 O4 -M shows the spin-state transition of cations from a low-spin state to an intermediate-spin state compared with FeCo2 O4 . Mössbauer spectra show that the Fe3+ ion in the octahedral site (0.76) of FeCo2 O4 -M is more than that of FeCo2 O4 (0.71), indicating the effective stimulus of metal cations in geometric sites by magnetic-field annealing. Furthermore, theoretical calculations demonstrate that the d-band centers (εd ) of Co 3d and Fe 3d in the tetrahedral and octahedral sites of the FeCo2 O4 -M nanofibers shift close to the Fermi level, revealing the enhanced mechanism of the ORR/OER activity.

Ferromagnetism of two-dimensional transition metal chalcogenides: both theoretical and experimental investigations.

In recent years, with the fast development of integrated circuit electronic devices and technologies, it has become urgent to improve the density of data storage and lower the energy losses of devices. Under these circumstances, two-dimensional (2D) materials, which have a smaller size and lower energy loss compared with bulk materials, are becoming ideal candidates for future spintronic devices. Among them, 2D transition metal chalcogenides (TMCs), which have excellent electronic and optical properties, have attracted great attention from researchers. However, most of them are intrinsically non-magnetic, which severely hinders their further applications in spintronics. Therefore, introducing intrinsic room-temperature ferromagnetism into 2D TMC materials has become an important issue in spintronics. In this work, we review the introduction of intrinsic ferromagnetism into typical 2D TMCs using various strategies, such as defect engineering, doping with transition metal elements, and phase transfer. Additionally, we found that their ferromagnetism could be adjusted via changing the experimental conditions, such as the nucleation temperature, ion irradiation dose, doping amount, and phase ratio. Finally, we provide some insight into prospective solutions for introducing ferromagnetism into 2D TMCs, hoping to shed some light on future spintronics development.

Cr cation-anchored carbon nanosheets: synthesis, paramagnetism and ferromagnetism.

Since the successfully synthesis of monolayer graphene, carbon-based materials have attracted wide and extensive attentions from researches. Due to the excellent transport capacity and conductivity, they are promising to be applied in electronic devices, even substituting the silicon-based electronic devices, optoelectronics and spintronics. Nevertheless, due to the non magnetic feature, many efforts have been devoted to endow carbon materials magnetism to apply them in the spintronic devices fabrication. Herein, a strategy of Cr cation solely anchored on two-dimensional carbon nanosheets by Cr-N bonds is developed, which introduces magnetism in carbon nanosheets. By extended x-ray absorption fine structure characterization, Cr cations are demonstrated to be atomically dispersed with Cr-N3coordination. And after Cr-N3anchored, carbon nanosheets exhibit ferromagnetic features with paramagnetic background. The magnetization varies with Cr content and reaches the maximum (Cr: 2.0%, 0.86 emu g-1) under 3 T at 50 K. The x-ray magnetic circular dichroism and first-principle calculations indicate that the magnetism is caused by the Cr3+component of the anchored Cr cations. This study sets a single cation anchoring carbon as a suitable candidate for future spintronics.

Observation of the antiferromagnetic spin Hall effect.

The discovery of the spin Hall effect1 enabled the efficient generation and manipulation of the spin current. More recently, the magnetic spin Hall effect2,3 was observed in non-collinear antiferromagnets, where the spin conservation is broken due to the non-collinear spin configuration. This provides a unique opportunity to control the spin current and relevant device performance with controllable magnetization. Here, we report a magnetic spin Hall effect in a collinear antiferromagnet, Mn2Au. The spin currents are generated at two spin sublattices with broken spatial symmetry, and the antiparallel antiferromagnetic moments play an important role. Therefore, we term this effect the 'antiferromagnetic spin Hall effect'. The out-of-plane spins from the antiferromagnetic spin Hall effect are favourable for the efficient switching of perpendicular magnetized devices, which is required for high-density applications. The antiferromagnetic spin Hall effect adds another twist to the atomic-level control of spin currents via the antiferromagnetic spin structure.

Effect of Rainfall and Temperature on Perithecium Production of Botryosphaeria dothidea on Cankered Apple Branches.

Botryosphaeria dothidea is a fungal pathogen causing canker, dieback, and fruit rot of apple trees worldwide. Ascospores are an important source of inoculum of Botryosphaeria canker in China. Experiments were conducted under both controlled and natural conditions to study perithecium formation in relation to environmental conditions. Perithecia of B. dothidea were detected on cankered lesions throughout the apple growing season except in July and in some years including August under natural conditions. On newly formed canker lesions, the first perithecium was detected as early as August, about 1 week after rainfall. Perithecia matured successively, lasting from early August to June of the next year, with a peak in late September or early October. Temperature and rainfall are two key environmental factors affecting perithecium formation. Under controlled conditions, perithecia were produced only on cankered shoots incubated at test temperatures of 20 and 25°C and wetted by >3 days of simulated rainfall per week. The number of perithecia produced on canker lesions increased with the increase in rainfall duration. Perithecia were formed on canker shoots exposed to rainfall only in June, July, and August but not in September. Rainfall of >3 days per week can be used to predict the initial formation of perithecia in the main apple production areas in China to assist disease management.

Interfacial Engineering of NiO/NiCo2O4 Porous Nanofibers as Efficient Bifunctional Catalysts for Rechargeable Zinc-Air Batteries.

To meet the crucial demand of regenerative Zn-air (ZA) batteries, low cost, highly efficient, and durable electrocatalysts for the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) are needed to replace the noble metal. Herein, porous NiO/NiCo2O4 nanofibers with superior electrocatalytic performance are synthesized by a facile electrospinning strategy with precursor transition metal salts in nonstoichiometric ratio, which confers the heterostructured NiO/NiCo2O4 with abundant interface-related active sites and electronic transmission channels. Density functional calculation results reveal the chemical bonds easily form between NiO and NiCo2O4 to facilitate the charge transfer, while X-ray absorption fine spectroscopy and X-ray photoelectron spectroscopy results demonstrate there are abundant Ni3+ and Co3+ species in NiO/NiCo2O4 due to the interfacial engineering. As a result, the NiO/NiCo2O4 porous nanofibers exhibit highly efficient and durable performances of OER and ORR in KOH solution, including a lower overpotential of 357 mV at 10 mA cm-2 (OER) and half-wave potential of 0.73 V (ORR) than that of the individual. What's more, the NiO/NiCo2O4-based ZA battery displays excellent specific capacities of 814.4 mA h g-1, and good cycling stability of 175 h. Additionally, the flexible ZA battery displays a long cycling life of 14 h and decent flexibility. This work shows that construction of the heterostructure could provide a feasible method to optimize their electrocatalytic performance and make them widely used in power source devices.

The Changing Factors Affecting Local Environmental Governance in China: Evidence from a Study of Prefecture-Level Cities in Guangdong Province.

This paper aims to examine the changing factors underlying China's environmental governance, by investigating the long-term dynamic impacts of related endogenous and exogenous factors and considering regional differences in these factors. The study estimated environmental regulation intensity and employed the geographical detector technique to analyze its driving factors, based on 21 prefecture-level cities in Guangdong Province, China, from 1990 to 2016. The results showed that environmental regulation intensity has increased in Guangdong Province over the past 27 years. The results also indicated that local environmental governance was affected by global-local interactions and changed based on different regional developmental phases. At first, factors within a region affected local environmental policies more significantly, such as economic development and urbanization. However, in the long run, globalization's impacts have been the most important factors influencing environmental governance. Further analysis showed that environmental regulation intensity in Guangdong Province's different regions was affected by different driven factors. Our analyses contribute to the understanding of China's environmental governance and have policy implications for environmental problem management and China's construction of an ecological civilization.

Depressive symptoms among Chinese residents: how are the natural, built, and social environments correlated?

BACKGROUND: Depression has become a severe societal problem in China. Although many studies have analyzed how environmental characteristics within neighborhoods affect depression, only a few have dealt with developing countries, and even fewer have considered built, natural, and social environments concurrently. METHODS: Based on a sample of 20,533 Chinese residents assessed in 2016, the present study examined associations between depressive symptoms and respondents' built, natural, and social environments. Depressive symptoms were measured using the Center for Epidemiologic Studies Depression Scale (CES-D), and multilevel regression models were fitted accounting for potential covariates. RESULTS: Results indicated that living in neighborhoods with more green spaces and a higher population density were negatively associated with CES-D scores. Living in neighborhoods with more social capital was protective against depression. Furthermore, results showed that the social environment moderated the association between the built environment and depression. CONCLUSIONS: Social environments moderate the relationship between the built environment and depression. As environments seem to interact with each other, we advise against relying on a single environment when examining associations with depressive symptoms.

Analogue of dynamic Hall effect in cavity magnon polariton system and coherently controlled logic device.

Cavity magnon polaritons are mixed quasiparticles that arise from the strong coupling between cavity photons and quantized magnons. Combining high-speed photons with long-coherence-time magnons, such polaritons promise to be a potential candidate for quantum information processing. For harnessing coherent information contained in spatially distributed polariton states, it is highly desirable to manipulate cavity magnon polaritons in a two-dimensional system. Here, we demonstrate that tunable cavity magnon polariton transport can be achieved by strongly coupling magnons to microwave photons in a cross-cavity. An analog to the dynamic Hall effect has been demonstrated in a planar cavity spintronic device, where the propagation of cavity-magnon-polaritons is deflected transversally due to hybrid magnon-photon dynamics. Implementing this device as a Michelson-type interferometer using the coherent nature of the dynamic Hall and longitudinal signals, we have developed a proof-of-principle logic device to control the amplitude of cavity-magnon-polaritons by encoding the input microwave phase.

Exploring the links between population density, lifestyle, and being overweight: secondary data analyses of middle-aged and older Chinese adults.

BACKGROUND: The increasing prevalence of obesity across all age groups has become a major health concern in China. Previous studies have found strong links between population density, sedentary lifestyle, and the risk of being overweight among adults and adolescents in Western countries. However, little research has been conducted to disentangle this relationship in China, which is rapidly urbanizing and densely populated. Compared to other age groups, middle-aged and older adults tend to have a higher risk of being overweight, which increases their risk of diabetes, high blood pressure, and other weight-related chronic diseases. In addition, they are especially sensitive to neighbourhood environmental factors such as population density. Therefore, we aimed to unravel the link between population density and the risk of being overweight among Chinese middle-aged and older adults, with a particular focus on the mediating role of lifestyle choices. METHODS: Data from the 2011 China Health and Retirement Longitudinal Study were analysed. Individuals (N = 5285) were sampled from 405 neighbourhoods nested within 150 cities. Body Mass Index (BMI) was calculated based on self-reported body weight and height (being overweight was defined as a BMI ≥ 24 kg/m2). Multilevel regression and mediation analyses were applied to explore associations between population density, a sedentary lifestyle, and the risk of being overweight. RESULTS: Middle-aged and older adults who lived in densely populated neighbourhoods had higher odds of being overweight. Further, this link was mediated by residents' mode of travel and physical exercise; specifically, these residents had higher odds of owning a car and spending lesser time on weekly physical exercise, thereby increasing their risk of being overweight. Furthermore, the association between car ownership and the odds of being overweight varied by neighbourhood population density. CONCLUSIONS: There was a positive association between neighbourhood population density and middle-aged and older adults' risk of being overweight. This relationship may exist because people who live in densely populated neighbourhoods tend to lead a sedentary lifestyle. Our findings also suggest that, in rapidly urbanizing countries, a sedentary lifestyle may be especially harmful to middle-aged and older adults who live in densely populated neighbourhoods.

Co and CeO2 co-decorated N-doping carbon nanofibers for rechargeable Zn-air batteries.

The heterogeneous Co and CeO2 co-decorated N-doping carbon nanofibers (Co-CeO2-N-C) were synthesized via the electrospinning technique. As the bifunctional electrocatalyst, Co-CeO2-N-C nanofibers show excellent oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) performance, owing to the higher degree of graphitization of carbon, the N-doping, and the formation of an interface between Co and CeO2. The liquid Zn-air battery based on Co-CeO2-N-C nanofibers displays excellent specific capacities (815.9 mA h g-1 at 5 mA cm-2), higher open circuit voltages (1.47 V), and good cycling stability (113 h). The corresponding flexible solid state Zn-air battery shows excellent cycling stability (11 h), and good flexibility. Our finding suggests that Co-CeO2-N-C nanofibers could serve as a new group of bifunctional electrocatalysts for OER and ORR with excellent performance, and make them promising for use in future electric vehicles, off-grid power sources, and portable electronics.

Direct imaging of dopant sites in rare-earth element-doped permanent magnet and correlated magnetism origin.

Identifying the dopants and their occupation sites in rare-earth-doped permanent magnets is critical not only to understand the mechanism of tuning their magnetic properties, but also to develop guiding principles to further improve their performance. In this study, we present a direct observation of the preferred atomic sites of La atoms in La-doped M-type SrFe12O19 hexaferrite. Our data solidly clarified that only the Sr2+ cations were replaced by La3+ cations, and the La-doping caused the changes in the valence states of iron cations located at the 4f1 and 2a crystallographic sites. First principles calculations further revealed that after La-doping, the changes in the spin states of the Fe3+ cations located at the 4f1 tetrahedral sites resulted in magnetization enhancement and those of the 2a octahedral sites contributed to electrical neutrality, well matching the experimental atomic-column resolution EELS and magnetic measurement results.

Cross-sectional associations between long-term exposure to particulate matter and depression in China: The mediating effects of sunlight, physical activity, and neighborly reciprocity.

BACKGROUND: Although numerous studies have speculated about the direct and indirect linkage between long-term air pollution (i.e., PM2.5) concentrations and mental health in developed countries, evidence for developing countries is limited. Our aim was to examine the mediation effects of sunlight, physical activity, and neighborly reciprocity on the association between air pollution and depression. METHODS: In a sample of 20,861 individuals in China in 2016, depression was measured using the Center for Epidemiological Studies Depression screener (CES-D) and linked to annual city-wide PM2.5 data. We used multilevel regression models to assess the associations between depressive symptoms and PM2.5 and tested the mediation of sunlight, physical activity, and neighborly reciprocity in this association. Propensity score matching was used to evaluate whether selection bias may affect the association between CES-D scores and PM2.5. RESULTS: PM2.5 concentration was positively associated with depression symptoms. All mediators were significantly and negatively associated with PM2.5. Our mediation analyses indicated that physical activity, neighborly reciprocity, and exposure to sunlight are important mechanisms through which PM2.5 affects depressive symptoms. LIMITATIONS: The limitations of the present study were the cross-sectional nature of the data and modifiable areal unit problem. CONCLUSIONS: Our findings suggest not only that PM2.5 is directly associated with depression, but also that this association seems to be partially mediated by physical activity, neighborly reciprocity, and sunlight.

Atomic-scale imaging of the ferrimagnetic/diamagnetic interface in Au-Fe3O4 nanodimers and correlated exchange-bias origin.

Exchange-biased magnetic heterostructures have become one of the research frontiers due to their significance in enriching the fundamental knowledge in nanomagnetics and promising diverse applications in the information industry. However, the physical origin of their exchange bias effect is still controversial. A key reason for this is the lack of unequivocal observations of interface growth. In this work, we fill this gap by experimentally imaging the ferrimagnetic/diamagnetic interfaces of Au-Fe3O4 nanodimers at the atomic level. A different physical mechanism from the reported mechanisms is found based on the atomic-resolution observation of their interfacial structure and electronic states, which reveals that the antiferromagnetic and ferromagnetic interactions of the formed weak/strong ferrimagnetic bilayer are responsible for the intrinsic exchange-bias origin in Au-Fe3O4 nanodimers. The theoretical quantitative analysis of the exchange bias shift based on the observed interfacial occupation model agrees well with the experimental value for the exchange bias effect, strongly verifying the proposed exchange-bias mechanism.