Terahertz electrical writing speed in an antiferromagnetic memory

The speed of writing of state-of-the-art ferromagnetic memories is physically limited by an intrinsic gigahertz threshold. Recently, realization of memory devices based on antiferromagnets, in which spin directions periodically alternate from one atomic lattice site to the next has moved research in an alternative direction. We experimentally demonstrate at room temperature that the speed of reversible electrical writing in a memory device can be scaled up to terahertz using an antiferromagnet. A current-induced spin-torque mechanism is responsible for the switching in our memory devices throughout the 12-order-of-magnitude range of writing speeds from hertz to terahertz. Our work opens the path toward the development of memory-logic technology reaching the elusive terahertz band

Molecular beam epitaxy of CuMnAs

We present a detailed study of the growth of the tetragonal polymorph of antiferromagnetic CuMnAs by the molecular beam epitaxy technique. We explore the parameter space of growth conditions and their effect on the microstructural and transport properties of the material. We identify its typical structural defects and compare the properties of epitaxial CuMnAs layers grown on GaP, GaAs and Si substrates. Finally, we investigate the correlation between the crystalline quality of CuMnAs and its performance in terms of electrically induced resistance switching.Comment: 10 pages, 8 figures and supplementary materia

Atomically sharp domain walls in an antiferromagnet

The interest in understanding scaling limits of magnetic textures such as domain walls spans the entire field of magnetism from its relativistic quantum fundamentals to applications in information technologies. The traditional focus of the field on ferromagnets has recently started to shift towards antiferromagnets which offer a rich materials landscape and utility in ultra-fast and neuromorphic devices insensitive to magnetic field perturbations. Here we report the observation that domain walls in an epitaxial crystal of antiferromagnetic CuMnAs can be atomically sharp. We reveal this ultimate domain wall scaling limit using differential phase contrast imaging within aberrationcorrected scanning transmission electron microscopy, which we complement by X-ray magnetic dichroism microscopy and ab initio calculations. We highlight that the atomically sharp domain walls are outside the remits of established spin-Hamiltonian theories and can offer device functionalities unparalleled in ferromagnets.Comment: 8 pages, 4 figures, Supplementary informatio

Global maps of soil temperature

Research in global change ecology relies heavily on global climatic grids derived from estimates of air temperature in open areas at around 2 m above the ground. These climatic grids do not reflect conditions below vegetation canopies and near the ground surface, where critical ecosystem functions occur and most terrestrial species reside. Here, we provide global maps of soil temperature and bioclimatic variables at a 1-km2 resolution for 0–5 and 5–15 cm soil depth. These maps were created by calculating the difference (i.e. offset) between in situ soil temperature measurements, based on time series from over 1200 1-km2 pixels (summarized from 8519 unique temperature sensors) across all the world\u27s major terrestrial biomes, and coarse-grained air temperature estimates from ERA5-Land (an atmospheric reanalysis by the European Centre for Medium-Range Weather Forecasts). We show that mean annual soil temperature differs markedly from the corresponding gridded air temperature, by up to 10°C (mean = 3.0 ± 2.1°C), with substantial variation across biomes and seasons. Over the year, soils in cold and/or dry biomes are substantially warmer (+3.6 ± 2.3°C) than gridded air temperature, whereas soils in warm and humid environments are on average slightly cooler (−0.7 ± 2.3°C). The observed substantial and biome-specific offsets emphasize that the projected impacts of climate and climate change on near-surface biodiversity and ecosystem functioning are inaccurately assessed when air rather than soil temperature is used, especially in cold environments. The global soil-related bioclimatic variables provided here are an important step forward for any application in ecology and related disciplines. Nevertheless, we highlight the need to fill remaining geographic gaps by collecting more in situ measurements of microclimate conditions to further enhance the spatiotemporal resolution of global soil temperature products for ecological applications

Dynamics and influencing factors of development of gullies in the Kokořínsko

Although gully erosion represents an important process of land degradation, only a few studies in the Czechia have quantified the gully erosion rate yet. Because of the complex and nonlinear dynamics, the estimation of the gully erosion rate requires a long term and technically difficult research. However, a recent methodological approach in dendrogeomorphology allows to reconstruct a gully development and assess gully erosion rate. Based on geodetic survey, a detailed mapping of four gullies in the Polomené Mountains was carried out. Subsequently, the gully erosion rate was evaluated by the analysis of 73 exposed roots of broadleaved trees. The first erosion episode was detected in 1981, however, most of the roots were exposed in the last 15 years. Gullies have been forming non-continuously showing median erosion rates between 10.0 to 13.4 mm/year. Even though topographic parameters and land use changes in drainage basin area may affect the intensity of erosion, most of the erosion episodes have been probably triggered by extreme rainfall events. This study exemplifies that intesive gully erosion may occur even on forest soils. Vegetation cover influences a morphology of gully slopes, but its ability to prevent intensive gully erosion is limited. Keywords: gully, erosion rate, exposed roots,..

Web standards and responsive webdesign

The Bachelor's thesis Web standards and responsive webdesign deals with methods and procedures that are suitable for developing responsive website. The thesis also includes familiarization with the origins and history of webdesign and related technologies that it draws upon. The thesis is devided into theoretical and practical subsection. Theoretical part deals with the history of the web, the development of HTML to its latest version of HTML5 and its semantics, Cascading Style Sheets and its innovations, history of web browsers and particularly techniques suitable for creating responsive web. The practical part is focused on creating a responsive website using methods and procedures derived from the theoretical subsection

Response of sedimentation and erosion rates to changing human pressure

While on the continental or global level and across the long time-scales, erosion and accumulation processes are largely governed by tectonics, terrain properties, geological settings and climate play a key role on the landscape or local levels and on short time scales. However, from the Neolithic onwards, human society has become an important factor affecting erosion-accumulation processes. As a result of agricultural activities, population expansion and land use changes soil has been washed downslope by soil erosion associated with formation of gullies. Furthermore, an increase of deposition rates was observed for colluvial, alluvial and lake deposits. The aim of this thesis is to review past soil erosion and accumulation processes connected with land use changes within the central Europe during the Holocene. 37 case studies documented generally strong relation between land use intensity and erosion and accumulation processes. First phase of anthropogenic accelerated erosion-accumulation processes was recorded in the late Eneolit period; however, the most remarkable acceleration of soil erosion occurred during landscape colonisation in the High Middle Ages. The second part of thesis aims at dating of two gullies in the Polomené hory Mts. Formation of gullies was studied using exposed roots. In..

Unmanned aerial systems for modelling air pollution removal by urban greenery

Urban greenery plays an important role in reducing air pollution, being one of the often-used, nature-based measures in sustainable and climate-resilient urban development. However, when modelling its effect on air pollution removal by dry deposition, coarse and time-limited data on vegetation properties are often included, disregarding the high spatial and temporal heterogeneity in urban forest canopies. Here, we present a detailed, physics-based approach for modelling particulate matter (PM10) and tropospheric ozone (O-3) removal by urban greenery on a small scale that eliminates these constraints. Our procedure combines a dense network of low-cost optical and electrochemical air pollution sensors, and a remote sensing method for greenery structure monitoring derived from Unmanned aerial systems (UAS) imagery processed by the Structure from Motion (SfM) algorithm. This approach enabled the quantification of species- and individual-specific air pollution removal rates by woody plants throughout the growing season, exploring the high spatial and temporal variability of modelled removal rates within an urban forest. The total PM10 and O-3 removal rates ranged from 7.6 g m(-2) (PM10) and 12.6 g m(-2) (O-3) for mature trees of Acer pseudoplatanus to 0.1 g m(-2) and 0.1 g m(-2) for newly planted tree saplings of Salix daphnoides. The present study demonstrates that UAS-SfM can detect differences in structures among and within canopies and by involving these characteristics, they can shift the modelling of air pollution removal towards a level of individual woody plants and beyond, enabling more realistic and accurate quantification of air pollution removal. Moreover, this approach can be similarly applied when modelling other ecosystem services provided by urban greenery.Web of Science78art. no. 12775

Systematic Study of Anisotropic Magnetoresistance in (Ga,Mn)As

AbstractWe systematically study the anisotropic magnetoresistance (AMR) on a series of optimized (Ga,Mn)As samples. The crystalline and non-crystalline contributions to the AMR were separated and an apparent higher-order term (of six-fold symmetry) was identified to be an artefact resulting from the presence of magnetic anisotropy of the material and of the residual fields of external superconducting magnets. In the broad range of nominal Mn concentrations from 2% to 11%, we find the non-crystalline contribution to dominate, although the crystalline terms become relatively more important for higher doping levels. We compare the AMR magnitude with the Boltzmann transport calculations based on the k·p mean-field kinetic-exchange model