Materials composed of two dimensional layers bonded to one another through weak van der Waals interactions often exhibit strongly anisotropic behaviors and can be cleaved into very thin specimens and ...sometimes into monolayer crystals. Interest in such materials is driven by the study of low dimensional physics and the design of functional heterostructures. Binary compounds with the compositions M X 2 and M X 3 where M is a metal cation and X is a halogen anion often form such structures. Magnetism can be incorporated by choosing a transition metal with a partially filled d-shell for M, enabling ferroic responses for enhanced functionality. Here a brief overview of binary transition metal dihalides and trihalides is given, summarizing their crystallographic properties and long-range-ordered magnetic structures, focusing on those materials with layered crystal structures and partially filled d-shells required for combining low dimensionality and cleavability with magnetism.
Local governments do not stand alone—they find themselves in new relationships not only with state and federal government, but often with a widening spectrum of other public and private organizations ...as well. The result of this re-forming of local governments calls for new collaborations and managerial responses that occur in addition to governmental and bureaucratic processes-as-usual, bringing locally generated strategies or what the authors call "jurisdiction-based management" into play. Based on an extensive study of 237 cities within five states, Collaborative Public Management provides an in-depth look at how city officials work with other governments and organizations to develop their city economies and what makes these collaborations work. Exploring the more complex nature of collaboration across jurisdictions, governments, and sectors, Agranoff and McGuire illustrate how public managers address complex problems through strategic partnerships, networks, contractual relationships, alliances, committees, coalitions, consortia, and councils as they function together to meet public demands through other government agencies, nonprofit associations, for-profit entities, and many other types of nongovernmental organizations. Beyond the "how" and "why," Collaborative Public Management identifies the importance of different managerial approaches by breaking them down into parts and sequences, and describing the many kinds of collaborative activities and processes that allow local governments to function in new ways to address the most nettlesome public challenges.
Ultrathin van der Waals materials and their heterostructures offer a simple, yet powerful platform for discovering emergent phenomena and implementing device structures in the two-dimensional limit. ...The past few years has pushed this frontier to include magnetism. These advances have brought forth a new assortment of layered materials that intrinsically possess a wide variety of magnetic properties and are instrumental in integrating exchange and spin-orbit interactions into van der Waals heterostructures. This Review Article summarizes recent progress in exploring the intrinsic magnetism of atomically thin van der Waals materials, manipulation of their magnetism by tuning the interlayer coupling, and device structures for spin- and valleytronic applications.
Since the discovery of Dirac physics in graphene, research in 2D materials has exploded with the aim of finding new materials and harnessing their unique and tunable electronic and optical ...properties. The follow‐on work on 2D dielectrics and semiconductors has led to the emergence and development of hexagonal boron nitride, black phosphorus, and transition metal disulfides. However, the spectrum of good insulating materials is still very narrow. Likewise, 2D materials exhibiting correlated phenomena such as superconductivity, magnetism, and ferroelectricity have yet to be developed or discovered. These properties will significantly enrich the spectrum of functional 2D materials, particularly in the case of high phase‐transition temperatures. They will also advance a fascinating fundamental frontier of size and proximity effects on correlated ground states. Here, a broad family of layered metal thio(seleno)phosphate materials that are moderate‐ to wide‐bandgap semiconductors with incipient ionic conductivity and a host of ferroic properties are reviewed. It is argued that this material class has the potential to merge the sought‐after properties of complex oxides with electronic functions of 2D and quasi‐2D electronic materials, as well as to create new avenues for both applied and fundamental materials research in structural and magnetic correlations.
Metal thiophosphates (MTPs) are a class of cleavable insulating materials with a common P2S6 structural framework. They span a very wide variety of transition metal cations, thus exhibiting ferroelectricity, magnetism, and optoelectronic properties, as well as rich solid‐state chemistry that can combine various properties within a single bulk, quasi‐2D, or prospectively 2D crystal. In this respect, MTP compounds can be viewed as a layered analogue to complex oxides.
We have examined the crystallographic and magnetic properties of single crystals of CrI3, an easily cleavable, layered and insulating ferromagnet with a Curie temperature of 61 K. Our X-ray ...diffraction studies reveal a first-order crystallographic phase transition occurring near 210–220 K upon warming, with significant thermal hysteresis. The low-temperature structure is rhombohedral (R3̅, BiI3-type) and the high-temperature structure is monoclinic (C2/m, AlCl3-type). We find evidence for coupling between the crystallographic and magnetic degrees of freedom in CrI3, observing an anomaly in the interlayer spacing at the Curie temperature and an anomaly in the magnetic susceptibility at the structural transition. First-principles calculations reveal the importance of proper treatment of the long-ranged interlayer forces, and van der Waals density functional theory does an excellent job of predicting the crystal structures and their relative stability. Calculations also suggest that the ferromagnetic order found in the bulk material may persist into monolayer form, suggesting that CrI3 and other chromium trihalides may be promising materials for spintronic and magnetoelectronic research.
•Proposed the addition of decision analysis methods to the Safe Route Planner.•Results of AHP, Fuzzy AHP, TOPSIS, Fuzzy TOPSIS and PROMETHEE were compared.•The results show the better performance of ...AHP, Fuzzy AHP and PROMETHEE.•The results of TOPSIS and Fuzzy TOPSIS are inconsistent with other methods.•Discounted Cumulative Gain is proposed to quantify the comparison results.
Motor vehicle crashes are a leading cause of death in the U.S. In order to reduce death and serious injury, road and traffic engineers manually evaluate road segments and visualize the safety level of roads. These existing risk maps can be confusing and must be manually interpreted by drivers to find the safest path from a source to a given destination; this can result in ignoring the safety of the routes by drivers. In addition, common navigation systems such as Google Maps and Waze present two or three alternative paths from a source to a given destination based on the travel time and distance. A navigation system is required to take the safety level of the road segments into consideration while suggesting a path. This navigation system needs to acquire knowledge from various sources, a user interface to obtain user preferences, and an inference engine to find the best paths. Such a system can still suggest multiple conflicting paths, such as shortest, fastest and safest paths. This paper presents the addition of a multi-criteria decision-making (MCDM) method, Analytical Hierarchy Process, to a previously designed Safe Route Planner to aid users in choosing the most suitable path among M alternative paths. Different MCDM methods can generate different results while applied to the same problem. There are a few comparative studies to compare the results of different Multi-Criteria Decision-Making (MCDM) methods. Therefore, a particular attention is devoted to comparing the results of five decision-making techniques, namely AHP, Fuzzy AHP, TOPSIS, Fuzzy TOPSIS and PROMETHEE through two real-world case studies. In addition, the comparative studies fail to adequately quantify the results of the MCDM methods; consequently, another aim of this research is to investigate the applicability of Spearman's rank correlation coefficient, Average Overlap and Discounted Cumulative Gain techniques to quantify the results of the MCDM methods.
Layered antiferromagnetism is the spatial arrangement of ferromagnetic layers with antiferromagnetic interlayer coupling. The van der Waals magnet chromium triiodide (CrI3) has been shown to be a ...layered antiferromagnetic insulator in its few-layer form, opening up opportunities for various functionalities in electronic and optical devices. Here we report an emergent nonreciprocal second-order nonlinear optical effect in bilayer CrI3. The observed second-harmonic generation (SHG; a nonlinear optical process that converts two photons of the same frequency into one photon of twice the fundamental frequency) is several orders of magnitude larger than known magnetization-induced SHG and comparable to the SHG of the best (in terms of nonlinear susceptibility) two-dimensional nonlinear optical materials studied so far (for example, molybdenum disulfide). We show that although the parent lattice of bilayer CrI3 is centrosymmetric, and thus does not contribute to the SHG signal, the observed giant nonreciprocal SHG originates only from the layered antiferromagnetic order, which breaks both the spatial-inversion symmetry and the time-reversal symmetry. Furthermore, polarization-resolved measurements reveal underlying C2h crystallographic symmetry-and thus monoclinic stacking order-in bilayer CrI3, providing key structural information for the microscopic origin of layered antiferromagnetism. Our results indicate that SHG is a highly sensitive probe of subtle magnetic orders and open up possibilities for the use of two-dimensional magnets in nonlinear and nonreciprocal optical devices.
Two-dimensional materials with intrinsic functionality are becoming increasingly important in exploring fundamental condensed matter science and for developing advanced technologies. Bulk crystals ...that can be exfoliated are particularly relevant to these pursuits as they provide the opportunity to study the role of physical dimensionality and explore device physics in highly crystalline samples and designer heterostructures in a routine manner. Magnetism is a key element in these endeavors; however, relatively few cleavable materials are magnetic and none possess magnetic order at ambient conditions. Here, we introduce Fe
GeTe
as a cleavable material with ferromagnetic behavior at room temperature. We established intrinsic magnetic order at room temperature in bulk crystals (Formula: see text = 310 K) through magnetization measurements and in exfoliated, thin flakes (Formula: see text ≈ 280 K) using the anomalous Hall effect. Our work reveals Fe
GeTe
as a prime candidate for incorporating intrinsic magnetism into functional van der Waals heterostructures and devices near room temperature.
Two-dimensional materials with intrinsic functionality are becoming increasingly important in exploring fundamental condensed matter science and for developing advanced technologies. Bulk crystals ...that can be exfoliated are particularly relevant to these pursuits as they provide the opportunity to study the role of physical dimensionality and explore device physics in highly crystalline samples and designer heterostructures in a routine manner. Magnetism is a key element in these endeavors; however, relatively few cleavable materials are magnetic and none possess magnetic order at ambient conditions. Here, we introduce Fe5–x GeTe2 as a cleavable material with ferromagnetic behavior at room temperature. We established intrinsic magnetic order at room temperature in bulk crystals ( T C = 310 K) through magnetization measurements and in exfoliated, thin flakes ( T C ≈ 280 K) using the anomalous Hall effect. Our work reveals Fe5GeTe2 as a prime candidate for incorporating intrinsic magnetism into functional van der Waals heterostructures and devices near room temperature.
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