Orbital torque of Cr-induced magnetization switching in perpendicularly magnetized Pt/Co/Pt/Cr heterostructures

The spin–orbit torque via the spin Hall effect of heavy metals has shown promising prospect in driving the magnetization switching in spintronic devices due to the generated spin current from heavy metals.Recently,the 3d-light metals have been predicted the ability to generate orbital current and the associated orbital torques from the orbital Hall effect.However,few experiments have been carried out since it is quite hard to directly detect the orbital current-generated orbital torque.Here,we report an effective method to demonstrate the strong orbital torques in light metal Cr through a conversion process from orbital current to spin current by introducing the Pt interfacial layer in perpendicularly magnetized symmetric Pt/Co/Pt structures.A quite large and monotonically growth of orbital torque efficiency in Pt/Co/Pt/Cr with the increase of the thickness of Cr layer is obtained with the largest effective orbital torque efficiency around 2.6 Oe/(MA·cm^(-2))(1 Oe=79.5775 A·m^(-1)).The ability of orbital torque to drive the magnetization switching is also reported with the critical switching current density down to the order of 106A·cm^(-2).Our findings prove the efficiency for switching the magnetization from light metal Cr layers through the orbital Hall effect.

Enhanced Spin–Orbit Torques in Graphene by Pt Adatoms Decoration

Graphene(Gr)with widely acclaimed characteristics,such as exceptionally long spin diffusion length at room temperature,provides an outstanding platform for spintronics.However,its inherent weak spin–orbit coupling(SOC)has limited its efficiency for generating the spin currents in order to control the magnetization switching process for applications in spintronics memories.Following the theoretical prediction on the enhancement of SOC in Gr by heavy atoms adsorption,here we experimentally observe a sizeable spin–orbit torques(SOTs)in Gr by the decoration of its surface with Pt adatoms in Gr/Pt(t Pt)/Fe Ni trilayers with the optimal damping-like SOT efficiency around 0.55 by 0.6-nm-thick Pt layer adsorption.The value is nearly four times larger than that of the Pt/Fe Ni sample without Gr and nearly twice the value of the Gr/Fe Ni sample without Pt adsorption.The efficiency of the enhanced SOT in Gr by Pt adatoms is also demonstrated by the field-free SOT magnetization switching process with a relatively low critical current density around 5.4 MA/cm^(2)in Gr/Pt/Fe Ni trilayers with the in-plane magnetic anisotropy.These findings pave the way for Gr spintronics applications,offering solutions for future low power consumption memories.

Heavy metal distribution of natural and reclaimed tidal riparian wetlands in south estuary, China

We evaluated the distribution and accumulation of Cd, Cr, Cu, Ni, Pb and Zn in two plant species (Scirpus tripueter Linn. and Cyperus malaccensis Lam.), in water and soils sampled from the reclaimed tidal riparian wetlands (RTRWs) and the natural riparian wetlands (NRWs) in the Pearl River Estuary (PRE). The results showed that the concentrations of studied heavy metals in soils exceeded theeco-toxic threshold recommended by US EPA. The concentrations of Cd, Cr and Zn in plants may lead to toxic effects. The heavy metalconcentrations were high in water and low in soils of RTRWs compared with that in the NRWs. The accumulation of heavy metalsin the roots of plants was higher in NRWs than those in RTRWs while the opposite result was found for heavy metal accumulation inshoots. Based on the bioaccumulation and translocation factors, the plants in NRWs had a higher capacity to accumulate heavy metalswhile higher abilities to transport heavy metals from roots to shoots were observed in RTRWs. Heavy metal contaminations in RTRWswere dominated by anthropogenic sources from both side uplands and river water, whereas in NRWs, the metal accumulations weresimultaneously affected by anthropogenic and natural

Eco-environmental water demands for the Baiyangdian Wetland

In recent years,the hydrological characters of Baiyangdian Wetland have changed greatly,which,in turn,influence the biotic component,the structure and function of the wetland ecosystem.In order to determine the demands for water resources of ecological wetland system,a method of ecological water level coefficient was suggested to calculate the water resources demands for wetland environment use.This research showed that the minimum coefficient is 0.94 and the optimal coefficient is more than 1.10.According to these two coefficients,the ecological water level and water quantity can be estimated.The results indicate that the amount of the minimal and optimal eco-environmental water require-ments are 0.87×10^(8) and 2.78×10^(8)m^(3) in average monthly,respectively,with the maximum eco-environmental water requirement in summer and the minimum in winter.The annual change of eco-environment water demand is in accord-ing with the climate change and hydrological characters.The method of ecological water level emphasizes that wetland ecosystem adapts to the hydrological conditions,so it can be used in practice well.

Spatial variations of river water quality in Pearl River Delta, China

在珀尔河三角洲(PRD ) ，河水质量由于人口增加和进行中的工业化和都市化逐渐地败坏了。在这研究， multivariate 统计数值方法被用来估计水质量空间模式并且在 PRD 识别水质量变化的特征。在一年 2005 和 2008 期间 PRD 监视的水质量在 25 个不同车站被进行。十七个水质量参数为进一步的学习被分析。变化(ANOVA ) 的单程的分析的结果显示除了空气温度，水温度和锌的所有参数在在干燥、湿的季节监视车站之中显示出重要差别。在 PRD 监视车站独立被分类进三统计上重要的簇在(D ^ 潜水艇连接 ^/D ^ 潜水艇最大 ^)< 2 在干燥、湿的季节分别地。三簇在 25 之中显示了河水质量的类似和不同监视车站，相应于重污染，中等污染和忽视污染。因此，这研究的结果是有用的评估水质量并且在 PRD 管理水资源[出版摘要]

Vertical characteristics of the Hani terrace paddyfield ecosystem in Yunnan,China

The Hani terrace paddyfield in Yunnan Province,China is categorized as a‘constructed wetland’under the Lamsar Convention classification.The Hani terrace paddyfield ranges from an altitude of 144 to 2000 m above sea level(ASL)in the southern slopes of the Ailao Mountains,angling down at a range of 15°to 75°.In this study,we investigated the ecosystem of the terrace paddyfields in the Mengpin and Quanfuzhuang administrative villages located at the center of the cultural heritage conservation district in the Hani terrace paddy-field.The Hani terrace paddyfield ecosystem structure is"forest-village-terrace paddyfield-river"in the order of descending altitude.Soil and water samples were sequen-tially taken from forests,villages and the terrace paddy-fields to be able to study the vertical characteristics of Hani’s terrace paddyfields.PO_(4)-P and NH_(3)-N in water were measured to test for water contamination.Seven soil nutrient factors were tested,including organic material(OM),char and nitrogen ratio(C/N),pH,total nitrogen(TN),total phosphorus(TP),available phosphorus(AP),and available potassium(AK).Soil quality was also eval-uated using the characteristics of the soil nutrient factors.Vertical changes in the landscape,wetland types,wetland plants,hydrology and soil nutrients were characterized.Results showed that:(1)Hani’s terrace paddyfield can be divided into five types of wetlands;the rice varieties and cultivation patterns vary in each type of wetland.(2)Hani’s terrace paddyfield has a great capacity for water conservation and a strong ability to purify contaminants.The impoundage of Hani’s terrace paddyfield is about 5050 m^(3)/hm^(2).Contaminants in the terrace paddyfield soils decrease exponentially with the decline in altitude.(3)Comparison of soil quality in five different land use types indicates decreasing soil quality from forest to terrace land to terrace paddyfield to water source.Except for headwater soil,single factors such as OM,TN and TP,and the comprehensive soil quality in individual sampling zones tend to increase with altitude elevation.Comprehensive soil quality in the Quanfuzhuang sampling zone is better than in the Mengpin sampling zone.Finally,a comparison of Hani’s terrace paddyfield with plain paddyfields and natural wetlands highlighted the vertical characteristics of Hani’s terrace paddyfield.

A novel herbivorous wood-borer insect outbreak triggers die-offs of a foundation plant species in coastal ecosystems

Introduction:Understanding the trophic interactions between plants and herbivorous insects is essential for managing the ecosystem health and sustainability in the context of climate change and anthropogenic disturbance.The Tamarix chinensis is a foundation plant species of salt marshes in northern China,which provides a variety of ecological functions and services in coastal ecosystems such as withstanding storm tide,conserving biodiversity,and preventing shoreline erosion.Outcomes:However,through long-term field observations,for the first time,we found that the health of this population has been suffering from the potential outbreak of a novel wood-borer insect(Zeuzera leuconotum Butler)under multiple stresses,contributing substantially to the degradation of the coastal salt marshes.Discussion and Conclusion:Therefore,there is urgent need and great significance to investigate the potential impact of this herbivorous wood-borer insects on health and sustainability of plant community in coastal ecosystems for in-depth understanding its degradation mechanisms.

Response of reed community to the environment gradientwater depth in the Yellow River Delta, China

We investigated and monitored a reed community in the fields.Data on the bio-ecological characteristics and β-diversity of reed communities in different environmental gradients(mainly based on water depth)of the Yellow River Delta were collected through multianalysis,extremum analysis and β-diversity index analysis.In accordance with the square sum of deviations(Ward)cluster analysis,10 sampling plots were divided into six types with the dominant plants in different plots varying according to the change in environmental gradients.The dominant plants in these plots varied from aquatic plants to xerophytes and salt tolerant plants as water depth decreased.The average height and diameter of the reeds at breast level were significantly correlated with the average water depth.The fitness curves of average density and coverage with average water depth were nonlinear.When the average water depth was 0.3 m,the average density and coverage of reeds reached the apex value,while the height and diameter of the reeds at breast level increased with the water depth.There were obvious changes to the environmental gradient in the Yellow River Delta.The transitional communities were also found to exist in the Yellow River Delta by β-diversity analysis.Vicarious species appeared with the change in water depth.The occurrence of substitute species is determined by the function of common species between adjacent belts.The different functions of common species led to differences in community structure and function and differences in dominant plants.The result reflects the variations of species present in different habitats and directly reflects environmental heterogeneity.The values of β-diversity indices of adjacent plots were higher than those of nonadjacent plots.There are transition zones between the xerophytes and aquatic plants in the Yellow River Delta.In an aquatic environment,the similarity of reed community is higher than that of xeromorphic plants.The β-diversity index can reflect plant succession trends caused by the change in environmental gradients in the Yellow River Delta.The β-diversity index reveals plant responses to changes in environmental gradient and is helpful in observing changes in patterns of species diversity in relation to environmental gradient change and evolving trends in the future,which in turn plays a prominent role when environmental water requirements of wetland are discussed.

Number and nest-site selection of breeding black-necked cranes over the past 40 years in the Longbao Wetland Nature Reserve,Qinghai,China

Black-necked crane(Grus nigricollis,BNC),facing serious threats from human activities and habitat variations,is an endangered species classified as vulnerable under the revised IUCN Red List.In this article,we investigated and analyzed the population and nesting microhabitat of BNCs in the Longbao National Nature Reserve(NNR)from 1978 to 2016,and found the number of BNCs increased from 24 in 1978 to 216 in 2016.This establishment of the Longbao NNR represented the activities of protecting endangered animal species are effective.However,the land cover classification results of Landsat images showed that the marsh wetland,which was the BNC’s primary habitat,decreased during 1978–2016,while artificial buildings increased,which affected the habitat of BNCs.The increase in average temperature over the past 40 years has also had an impact on the number of BNCs.BNCs preferred to nest in marsh wetlands or on islands with open water or star-like distributions through observation.The results of the principal component analysis showed that the nearest distance between nests and habitat type were the primary factors influencing nesting site selection.To protect BNC,we suggest decreasing wetland fragmentation,reducing habitat degradation and providing an undisturbed habitat.

Field-free approaches for deterministic spin–orbit torque switching of the perpendicular magnet

All-electrical driven magnetization switching attracts much attention in next-generation spintronic memory and logic devices,particularly in magnetic random-access memory(MRAM)based on the spin–orbit torque(SOT),i.e.SOT-MRAM,due to its advantages of low power consumption,fast write/read speed,and improved endurance,etc.For conventional SOT-driven switching of the magnet with perpendicular magnetic anisotropy,an external assisted magnetic field is necessary to break the inversion symmetry of the magnet,which not only induces the additional power consumption but also makes the circuit more complicated.Over the last decade,significant effort has been devoted to field-free magnetization manipulation by using SOT.In this review,we introduce the basic concepts of SOT.After that,we mainly focus on several approaches to realize the field-free deterministic SOT switching of the perpendicular magnet.The mechanisms mainly include mirror symmetry breaking,chiral symmetry breaking,exchange bias,and interlayer exchange coupling.Furthermore,we show the recent progress in the study of SOT with unconventional origin and symmetry.The final section is devoted to the industrial-level approach for potential applications of field-free SOT switching in SOT-MRAM technology.