Computers Math

A research team has discovered magnetic phenomena in antiferromagnets that could pave the way to developing faster and more efficient data storage.
How do magnetic waves behave in antiferromagnets and how do they spread? What role do “domain walls” play in the process? And what could this mean for the future of data storage? These questions are the focus of a recent publication in the journal Physical Review Letters from an international research team led by Konstanz physicist Dr Davide Bossini. The team reports on magnetic phenomena in antiferromagnets that can be induced by ultrafast (femtosecond) laser pulses and with the potential to endow the materials with new functionalities for energy-efficient and ultrafast data storage applications.
Demand for storage capacity is growing faster than the available infrastructure
The wildly increasing use of big data technologies and cloud-based data services means that the global demand for data storage is constantly expanding — along with the need for ever-faster data processing. At the same time, the currently available technologies will not be able to keep up forever. “The estimates say that the growing demand can only be met for a limited period of about 10 years, if no novel, more efficient technologies for data storage and processing can be developed in the meantime,” says physicist Dr Davide Bossini from the University of Konstanz and lead author of the study.
To prevent a data crisis from taking place, it will not be enough to simply keep building more and more data centres, operating at the current state-of-the art. The technologies of the future must also be faster and more energy-efficient than traditional mass data storage, based on magnetic hard disks. One class of materials, antiferromagnets, is a promising candidate for developing the next generation of information technology.
The structure of antiferromagnets
We are all familiar with household magnets made from iron or other ferromagnetic materials. These materials have atoms that are magnetically all oriented in the same direction — like small needles of a compass — so that a magnetic polarization (magnetization) occurs that affects the surrounding environment. The antiferromagnets, by contrast, have atoms with alternating magnetic moments that cancel each other out. Antiferromagnets thus have no net magnetization and therefore no magnetic impact on the surrounding environment. More

The discovery of isotopes in the early 20th century marked a key moment in the history of physics and led to a much more refined understanding of the atomic nucleus. Isotopes are ‘versions’ of a given element of the periodic table that bear the same number of protons but a different number of neutrons, and therefore vary in mass. These differences in mass can radically alter certain physical properties of the atoms, such as their radioactive decay rates, their possible reaction pathways in nuclear fission reactors, and much more.
While most isotopes of an element share similar chemical properties, there is one notable exception: hydrogen isotopes. Most hydrogen atoms on Earth contain only one proton and one electron, but there exist hydrogen isotopes which also have one neutron (deuterium) or two neutrons (tritium). Deuterium, which essentially weighs twice as much as ‘normal’ hydrogen, has found many practical and scientific uses. For example, it can be used to label and track molecules such as proteins to investigate biochemical processes. It can also be strategically used in drugs to reduce their metabolic rate and increase their half-life in the body.
Another important application of deuterium exists in the field of semiconductor electronics. The surface of silicon-based semiconductors has to be ‘passivated’ with hydrogen to ensure silicon atoms don’t come off (desorb) easily, thereby increasing the durability of microchips, batteries, and solar cells. However, through mechanisms that are still not completely understood, passivation with deuterium instead of hydrogen results in desorption probabilities about one hundred times lower, implying that deuterium may soon become an indispensable ingredient in electronic devices. Unfortunately, both the procurement of deuterium and available techniques to enrich silicon surfaces with it are very energy inefficient or require very expensive deuterium gas.
Fortunately, at Nagoya City University (NCU), Japan, a team of scientists led by Professor Takahiro Matsumoto have found an energy-efficient strategy to enrich silicon surfaces using a dilute deuterium solution. This study, which was published in Physical Review Materials, was carried out in collaboration with Dr. Takashi Ohhara of Japan Atomic Energy Agency and Dr. Yoshihiko Kanemitsu from Kyoto University.
The researchers found that a peculiar exchange reaction from hydrogen to deuterium can occur on the surface of nanocrystalline silicon (n-Si). They demonstrated this reaction in thin n-Si films submerged in a deuterium-containing solution using inelastic neutron scattering. This spectroscopy technique involves irradiating neutrons onto a sample and analyzing the resulting atomic motions or crystal vibrations. These experiments, coupled with other spectroscopy methods and energy calculations based on quantum mechanics, revealed the underlying mechanisms that favor the replacement of hydrogen terminations on the surface of n-Si with deuterium: The exchange process is closely related to differences in the surface vibrational modes between hydrogen- and deuterium-terminated n-Si. “We achieved a fourfold increase in the concentration of surface deuterium atoms on n-Si in our experiments performed in the liquid phase,” highlights Dr. Matsumoto, “We also proposed a gas-phase enrichment protocol for n-Si that, according to our theoretical calculations, could enhance the rate of deuterium enrichment 15-fold.”
This innovative strategy of exploiting quantum effects on the surface of n-Si could pave the way to new methods to procure and utilize deuterium. “The efficient hydrogen-to-deuterium exchange reaction we reported may lead to sustainable, economically feasible, and environment-friendly deuterium enrichment protocols, leading to more durable semiconductor technology,” concludes Dr. Matsumoto.
The NCU team also stated that “It has been theoretically predicted that the heavier the hydrogen is, the higher the efficiency of the exchange reaction is. Thus, we can expect more efficient enrichment of tritium atoms on n-Si, which leads to the possibility of purifying tritium contaminated water. We believe that this is an issue that must be urgently solved.”
Let us hope the findings of this work allow us to benefit more from the heavier isotopes of hydrogen without taking a toll on our planet.
Story Source:
Materials provided by Nagoya City University. Note: Content may be edited for style and length. More

Scientists at DESY have built a compact electron camera that can capture the inner, ultrafast dynamics of matter. The system shoots short bunches of electrons at a sample to take snapshots of its current inner structure and is the first such electron diffractometer that uses Terahertz radiation for pulse compression. The developer team around DESY scientists Dongfang Zhang and Franz Kärtner from the Center for Free-Electron Laser Science CFEL validated their Terahertz-enhanced ultrafast electron diffractometer with the investigation of a silicon sample and present their work in the first issue of the journal Ultrafast Science, a new title in the Science group of scientific journals.
Electron diffraction is one way to investigate the inner structure of matter. However, it does not image the structure directly. Instead, when the electrons hit or traverse a solid sample, they are deflected in a systematic way by the electrons in the solid’s inner lattice. From the pattern of this diffraction, recorded on a detector, the internal lattice structure of the solid can be calculated. To detect dynamic changes in this inner structure, short bunches of sufficiently bright electrons have to be used. “The shorter the bunch, the faster the exposure time,” says Zhang, who is now a professor at Shanghai Jiao Tong University. “Typically, ultrafast electron diffraction (UED) uses bunch lengths, or exposure times, of some 100 femtoseconds, which is 0.1 trillionths of a second.”
Such short electron bunches can be routinely produced with high quality by state-of-the-art particle accelerators. However, these machines are often large and bulky, partly due to the radio frequency radiation used to power them, which operates in the Gigahertz band. The wavelength of the radiation sets the size for the whole device. The DESY team is now using Terahertz radiation instead with roughly a hundred times shorter wavelengths. “This basically means, the accelerator components, here a bunch compressor, can be a hundred times smaller, too,” explains Kärtner, who is also a professor and a member of the cluster of excellence “CUI: Advanced Imaging of Matter” at the University of Hamburg.
For their proof-of-principle study, the scientists fired bunches with roughly 10,000 electrons each at a silicon crystal that was heated by a short laser pulse. The bunches were about 180 femtoseconds long and show clearly how the crystal lattice of the silicon sample quickly expands within a picosecond (trillionths of a second) after the laser hits the crystal. “The behaviour of silicon under these circumstances is very well known, and our measurements fit the expectation perfectly, validating our Terahertz device,” says Zhang. He estimates that in an optimised set-up, the electron bunches can be compressed to significantly less than 100 femtoseconds, allowing even faster snapshots.
On top of its reduced size, the Terahertz electron diffractometer has another advantage that might be even more important to researchers: “Our system is perfectly synchronised, since we are using just one laser for all steps: generating, manipulating, measuring and compressing the electron bunches, producing the Terahertz radiation and even heating the sample,” Kärtner explains. Synchronisation is key in this kind of ultrafast experiments. To monitor the swift structural changes within a sample of matter like silicon, researchers usually repeat the experiment many times while delaying the measuring pulse a little more each time. The more accurate this delay can be adjusted, the better the result. Usually, there needs to be some kind of synchronisation between the exciting laser pulse that starts the experiment and the measuring pulse, in this case the electron bunch. If both, the start of the experiment and the electron bunch and its manipulation are triggered by the same laser, the synchronisation is intrinsically given.
In a next step, the scientists plan to increase the energy of the electrons. Higher energy means the electrons can penetrate thicker samples. The prototype set-up used rather low-energy electrons and the silicon sample had to be sliced down to a thickness of just 35 nanometres (millionths of a millimetre). Adding another acceleration stage could give the electrons enough energy to penetrate 30 times thicker samples with a thickness of up to 1 micrometre (thousandth of a millimetre), as the researchers explain. For even thicker samples, X-rays are normally used. While X-ray diffraction is a well established and hugely successful technique, electrons usually do not damage the sample as quickly as X-rays do. “The energy deposited is much lower when using electrons,” explains Zhang. This could prove useful when investigating delicate materials.
This work has been supported by the European Research Council under the European Union’s Seventh Framework Program (FP7/2007-2013) through the Synergy Grant AXSIS (609920), Project KA908-12/1 of the Deutsche Forschungsgemeinschaft, and the accelerator on a chip program (ACHIP) funded by the Gordon and Betty Moore foundation (GBMF4744).
DESY is one of the world’s leading particle accelerator centres and investigates the structure and function of matter — from the interaction of tiny elementary particles and the behaviour of novel nanomaterials and vital biomolecules to the great mysteries of the universe. The particle accelerators and detectors that DESY develops and builds at its locations in Hamburg and Zeuthen are unique research tools. They generate the most intense X-ray radiation in the world, accelerate particles to record energies and open up new windows onto the universe. DESY is a member of the Helmholtz Association, Germany’s largest scientific association, and receives its funding from the German Federal Ministry of Education and Research (BMBF) (90 per cent) and the German federal states of Hamburg and Brandenburg (10 per cent). More

For the more than 5 million people in the world who have undergone an upper-limb amputation, prosthetics have come a long way. Beyond traditional mannequin-like appendages, there is a growing number of commercial neuroprosthetics — highly articulated bionic limbs, engineered to sense a user’s residual muscle signals and robotically mimic their intended motions.
But this high-tech dexterity comes at a price. Neuroprosthetics can cost tens of thousands of dollars and are built around metal skeletons, with electrical motors that can be heavy and rigid.
Now engineers at MIT and Shanghai Jiao Tong University have designed a soft, lightweight, and potentially low-cost neuroprosthetic hand. Amputees who tested the artificial limb performed daily activities, such as zipping a suitcase, pouring a carton of juice, and petting a cat, just as well as — and in some cases better than — those with more rigid neuroprosthetics.
The researchers found the prosthetic, designed with a system for tactile feedback, restored some primitive sensation in a volunteer’s residual limb. The new design is also surprisingly durable, quickly recovering after being struck with a hammer or run over with a car.
The smart hand is soft and elastic, and weighs about half a pound. Its components total around $500 — a fraction of the weight and material cost associated with more rigid smart limbs.
“This is not a product yet, but the performance is already similar or superior to existing neuroprosthetics, which we’re excited about,” says Xuanhe Zhao, professor of mechanical engineering and of civil and environmental engineering at MIT. “There’s huge potential to make this soft prosthetic very low cost, for low-income families who have suffered from amputation.”
Zhao and his colleagues have published their work today in Nature Biomedical Engineering. Co-authors include MIT postdoc Shaoting Lin, along with Guoying Gu, Xiangyang Zhu, and collaborators at Shanghai Jiao Tong University in China. More

Quantum engineers from UNSW Sydney have removed a major obstacle that has stood in the way of quantum computers becoming a reality: they discovered a new technique they say will be capable of controlling millions of spin qubits — the basic units of information in a silicon quantum processor.
Until now, quantum computer engineers and scientists have worked with a proof-of-concept model of quantum processors by demonstrating the control of only a handful of qubits.
But with their latest research, published today in Science Advances, the team have found what they consider ‘the missing jigsaw piece’ in the quantum computer architecture that should enable the control of the millions of qubits needed for extraordinarily complex calculations.
Dr Jarryd Pla, a faculty member in UNSW’s School of Electrical Engineering and Telecommunications says his research team wanted to crack the problem that had stumped quantum computer scientists for decades: how to control not just a few, but millions of qubits without taking up valuable space with more wiring, using more electricity, and generating more heat.
“Up until this point, controlling electron spin qubits relied on us delivering microwave magnetic fields by putting a current through a wire right beside the qubit,” Dr Pla says.
“This poses some real challenges if we want to scale up to the millions of qubits that a quantum computer will need to solve globally significant problems, such as the design of new vaccines. More

Robots that need to use their arms to make their way across treacherous terrain just got a speed upgrade with a new path planning approach, developed by University of Michigan researchers.
The improved algorithm path planning algorithm found successful paths three times as often as standard algorithms, while needing much less processing time.
A new algorithm speeds up path planning for robots that use arm-like appendages to maintain balance on treacherous terrain such as disaster areas or construction sites, U-M researchers have shown. The improved path planning algorithm found successful paths three times as often as standard algorithms, while needing much less processing time.
“In a collapsed building or on very rough terrain, a robot won’t always be able to balance itself and move forward with just its feet,” said Dmitry Berenson, associate professor of electrical and computer engineering and core faculty at the Robotics Institute.
“You need new algorithms to figure out where to put both feet and hands. You need to coordinate all these limbs together to maintain stability, and what that boils down to is a very difficult problem.”
The research enables robots to determine how difficult the terrain is before calculating a successful path forward, which might include bracing on the wall with one or two hands while taking the next step forward. More

People’s personality — such as how extroverted or introverted they are — and their gender can be linked to how they interact online, and whether they prefer interacting with a system rather than with other people.
In a study, a team of researchers found that people considered websites more interactive if they had tools to facilitate communication between users, often referred to as computer-mediated communication, or CMC. However, male extroverts also considered sites with tools that let them interact with the computer, called human-computer interaction, or HCI, to be more interactive compared to extroverted women, who viewed sites with CMC tools to be more interactive.
“When you go to a website — for example, the Google search engine — you’re essentially engaging in HCI, which is different from CMC, which is when you’re communicating with other humans through computer technology,” said S. Shyam Sundar, James P. Jimirro Professor of Media Effects in the Donald P. Bellisario College of Communications and co-director of the Media Effects Research Laboratory. “When we talk about HCI here, it’s really about the degree to which the system or the machine allows us to interact with it, and it includes everything from how we swipe and tap on our mobile devices, to how we try to access different information through links on a website. When we talk about CMC, it is about the tools to chat with somebody else, like a customer service agent through an online portal, or when we’re having a video chat via zoom, for example.”
Knowing who your web visitors are and what engages them is an important part of creating good user experiences, added Sundar, who is also an affiliate of the Institute for Computational and Data Science. “For developers, it’s useful to know who will appreciate what types of interactivity that you have to offer, or what kind of interactivity should you offer to which kind of people.
“These are actually quite important business decisions, because they cost a lot of money and have a lot of backend consequences,” said Sundar. For example, in an e-commerce site, which may be primarily trafficked by women, the findings suggest that efforts should be made to provide ways to talk to other people, such as chat tools, rather than simply tools to interact with the computer, such as being able to turn an image of a product in all directions.
Real world behaviors in the virtual world
When people use websites, many of the habits and behaviors they have adopted in real life influence their behaviors online, said Yan Huang, assistant professor of integrated strategic communication in the Jack J. Valenti School of Communication, University of Houston and first author of the paper. The study is in line with that, she added, demonstrating how people who are extroverted in real life also like to interact in virtual settings. More

New research published in Scientific Reports has revealed that a simple but robust algorithm can help engineers to improve the design of cellular materials that are used in a variety of diverse applications ranging from defence, bio-medical to smart structures and the aerospace sector.
The way in which cellular materials will perform can be uncertain and so calculations to help engineers predict how they will react for a particular design, for a given set of loads, conditions and constraints, can help maximise their design and subsequent performance.
The research collaborators at the Faculty of Science and Engineering, Swansea University, Indian Institute of Technology Delhi and Brown University, USA, found that running specialised calculations can help engineers to find the optimum micro-structure for cellular materials that are used for a wide range of purposes, from advanced aerospace applications to stents used for blocked arteries.
Research author Dr Tanmoy Chatterjee said: “This paper is the result of one year of sustained collaborative research. The results illustrate that uncertainties in the micro-scale can drastically impact the mechanical performance of metamaterials. Our formulation achieved novel microstructure designs by employing computational algorithms which follow the evolutionary principles of nature.”
Co-author Professor Sondipon Adhikari explains:
“This approach allowed us to achieve extreme mechanical properties involving negative Poisson’s ratio (auxetic metamaterial) and elastic modulus. The ability to manipulate extreme mechanical properties through novel optimal micro-architecture designs will open up new possibilities for manufacturing and applications.”
Story Source:
Materials provided by Swansea University. Note: Content may be edited for style and length. More