Probing magnetic ordering in air stable iron-rich van der Waals minerals

In the rapidly expanding field of two-dimensional materials, magnetic monolayers show great promise for the future applications in nanoelectronics, data storage, and sensing. The research in intrinsically magnetic two-dimensional materials mainly focuses on synthetic iodide and telluride based compounds, which inherently suffer from the lack of ambient stability. So far, naturally occurring layered magnetic materials have been vastly overlooked. These minerals offer a unique opportunity to explore air-stable complex layered systems with high concentration of local moment bearing ions. We demonstrate magnetic ordering in iron-rich two-dimensional phyllosilicates, focusing on mineral species of minnesotaite, annite, and biotite. These are naturally occurring van der Waals magnetic materials which integrate local moment baring ions of iron via magnesium/aluminium substitution in their octahedral sites. Due to self-inherent capping by silicate/aluminate tetrahedral groups, ultra-thin layers are air-stable. Chemical characterization, quantitative elemental analysis, and iron oxidation states were determined via Raman spectroscopy, wavelength disperse X-ray spectroscopy, X-ray absorption spectroscopy, and X-ray photoelectron spectroscopy. Superconducting quantum interference device magnetometry measurements were performed to examine the magnetic ordering. These layered materials exhibit paramagnetic or superparamagnetic characteristics at room temperature. At low temperature ferrimagnetic or antiferromagnetic ordering occurs, with the critical ordering temperature of 38.7 K for minnesotaite, 36.1 K for annite, and 4.9 K for biotite. In-field magnetic force microscopy on iron bearing phyllosilicates confirmed the paramagnetic response at room temperature, present down to monolayers.Comment: 19 pages, 6 figure

Incorporating statistical model error into the calculation of acceptability prices of contingent claims

The determination of acceptability prices of contingent claims requires the choice of a stochastic model for the underlying asset price dynamics. Given this model, optimal bid and ask prices can be found by stochastic optimization. However, the model for the underlying asset price process is typically based on data and found by a statistical estimation procedure. We define a confidence set of possible estimated models by a nonparametric neighborhood of a baseline model. This neighborhood serves as ambiguity set for a multistage stochastic optimization problem under model uncertainty. We obtain distributionally robust solutions of the acceptability pricing problem and derive the dual problem formulation. Moreover, we prove a general large deviations result for the nested distance, which allows to relate the bid and ask prices under model ambiguity to the quality of the observed data.© The Author(s) 201

Metadata record for: COVIDiSTRESS Global Survey dataset on psychological and behavioural consequences of the COVID-19 outbreak

This dataset contains key characteristics about the data described in the Data Descriptor COVIDiSTRESS Global Survey dataset on psychological and behavioural consequences of the COVID-19 outbreak. Contents: 1. human readable metadata summary table in CSV format 2. machine readable metadata file in JSON forma

Performance and limitations of MoS2/Ti composite coated inserts

Self-lubricating low friction MoS2/Ti composite coatings were deposited onto hard coated carbide inserts using a hybrid process 2 and were tested for dry high-speed milling and turning of steel. Dry machining is an important objective in industry to reduce environmental and production costs. It was shown that dry machining using MoS2/Ti composite coatings is possible in some 2 cases. Following an already good knowledge in low speed dry operations including drilling, tapping and threading, the coatings were tested under dry high-speed machining operations (milling and turning) where the temperatures involved are higher. Cutting tool parameters and tool grade and geometry were found to have an influence on the performance of the tools. Temperature and oxidation were investigated separately and correlated to the mechanical, chemical, oxidation and structural behaviour of the tools during machining tests

Performance and limitation of hybrid PECVD (hard coating)—PVD magnetron sputtering (MoS2/Ti composite) coated inserts tested for dry high speed milling of steel and grey cast iron

In the industry, High Speed Machining (HSM) is recognised as one of the key manufacturing technologies for higher productivity and lower production costs. Existing cutting tools are coated to improve the tool life and the performance. These coatings are all based on the principle that the coating is much harder than the work piece material. The objective of this paper is to present the new coatings for cutting tools based on a new approach: Low friction self-lubricant MoS2/Ti composite coatings (MoST) deposited by PVD magnetron sputtering technique. Dry machining (DM) is an important objective in machining industry to reduce environmental- and production costs. DM using MoST is possible in some cases: because of the low friction, the use of coolant is not necessary. Also, better chip evacuation and a smoother cutting process will occur, which can lead to higher accuracy of products. The paper included an assessment of machining performance of state of the art PECVD coated inserts (grade, geometry, coating). The consortium included manufacturers of milling machines and lathes, a coating company, a tool manufacturer, a university and two research institutes. Partners have contributed their particular expertise to the paper. The main results obtained with these new ‘'hybrid’’ inserts are: (1) Tools with MoST can be used in dry milling operations at normal cutting speeds; (2) MoST coatings reach good tool life (1.5–2 times longer than ‘State of the art’ tools) at normal cutting speeds