CAPTION For the studies, the physicist uses dilution refrigerators, among others. The refrigerators reach very low temperatures near absolute zero of minus 273°C.

Fundamental research to understand the dynamics in ferromagnets, EUR 2 million for five years

The "QuantumMagnonics" project of Dr. Martin Weides of the Physikalisches Institut of KIT deals with dynamic processes inside ferromagnets, such as iron or cobalt. Results of his fundamental research might be used for magnetic data processing components. The Research Council of the European Union funds the project with EUR 2 million.

"We are interested in the behavior of ferromagnets in the quantum regime," the physicist says. To explore physical processes in the atomic range, the researcher studies layers of thin material films structured in the nanometer range. These films are produced by KIT's DFG Center for Functional Nanostructures. With the help of experiments complementing and extending conventional measurement methods of classical physics, Weides hopes to better understand damping - loss - of energy while passing the magnetized material. Work focuses on intrinsic rotations of the individual electrons, called spins. The project is aimed at generating a single spin wave excited by an electromagnetic impulse. To measure the dynamic processes of the excited state, quantum bits, briefly called qubits, are to be applied as detectors and information units. The long project title is "QuantumMagnonics - Coupling of Spin Waves with Superconducting Quantum Circuits for the Generation and Detection of Individual Spin Waves." This fundamental research is expected to produce findings that will be of relevance to the use of magnetic materials in data processing, e.g. for storage media or logics elements.

One third of the funds of EUR 2 million granted by the European Union for five years will be spent by Weides for purchasing measurement instruments. Two thirds of the funds will be used to cover personnel costs for doctoral students and post-docs involved in the project. For his experimental studies, the physicist among others applies dilution refrigerators that reach extremely low temperatures near absolute zero of minus 273°C.

With ERC Consolidator Grants, the European Research Council (ERC) support projects of excellent scientists, who were conferred the doctorate seven to twelve years ago. The ERC was established in 2007 as an institution to fund fundamental pioneer research in Europe. "Thanks to funding under the EU program, we will be able to catch up with Japan and the USA that play a major role in this research area," Weides says. The project at KIT's Physikalisches Institut is based on the long-term research of the physicist, who has been working as a research assistant in the research group of Professor Alexey Ustinov since 2012. Before, the expert for solid-state physics and superconductors worked at Forschungszentrum Jülich and the University of California, Santa Barbara, among others. 

Weides has acquired the meanwhile seventh ERC Grant for the KIT. Before, renowned ERC funds were granted to Dr. Regina Hoffmann, Physikalisches Institut, in 2009, Dr. Matthias Schneider, Institute of Meteorology and Climate Research, in 2010, Professor Holger Puchta of the Botanical Institute, Professor Christian Koos of the Institute of Photonics and Quantum Electronics, and Dr. Alexander Nesterov-Müller of the Institute of Microstructure Technology in 2011, as well as to Erin Koos of the Institute of Mechanical Process Engineering and Pavel Levkin of the Institute of Toxicology and Genetics in 2013.

Microscopic image of the topological insulator Bismuth-Rhodium-Iodine (Bi14Rh3I9). The engraved letters BiRhI act as artificially introduced steps at the crystal surface.   Credit  M. Morgenstern, RWTH Aachen

In the latest issue of the journal Nature Physics, German Scientists report that they could observe experimentally the current flow along channels at the crystal surfaces of topological insulators. The channels are less than one nanometer wide and extend along atomic steps of the crystal lattice. The scientists demonstrated also how these steps can be introduced in any arrangement.

Topological insulators are a hot topic in materials physics. The most prominent feature of these materials is that they act as both insulators and conductors, with their interior preventing the flow of electrical currents while their edges or surfaces allow the movement of charge.

German Scientist from RWTH Aachen, Research Center Jülich, TU Dresden and of the Leibniz Institute for Solid State and Materials Research Dresden report that the current flow on the surface of a topological insulator is channeled along tiny paths, which have been theoretically calculated and experimentally observed. Their work has been published in the issue from March 2, 2015 of the journal Nature Physics. There they show for Bismuth-Rhodium-Iodine that these channels are tied to one dimensional surface features and run along steps formed by the edges of atomic layers. Scanning tunneling spectroscopy reveals the electron channels to be continuous in both energy and space and less than one nanometer wide.

Due to the properties of topological insulators, electric current flows unimpeded within these channels while charge can barely move from one channel to another. In this way, the surface acts as a set of electric wires that is defined by the atomic steps at the crystals surface. The scientists demonstrated that the surface can be engraved in any arrangement, allowing channel networks to be patterned with nanometer precision. The channeled current flow enables the transport of electrons while preventing the "scattering" typically associated with power consumption, in which electrons deviate from their trajectory. Thus, the resulting energy losses and heat generation are substantially diminished. These properties make topological insulators interesting for application in electronics. Furthermore, they are expected to enable novel types of information processing such as spintronics or quantum supercomputation. However, the prerequisite for the development of new devices based on topological insulators is a profound understanding of these quantum phenomena. The recent publication marks a milestone in this direction.

During the last decade great effort are being made worldwide to investigate and to describe the transport in topological insulators. In 2013 the team of Professor Michael Ruck at TU Dresden has succeeded for the first time in growing single crystals of Bismuth-Rhodium-Iodine. Jointly with theoreticians from the Leibniz-Institute for Solid State and Materials Research Dresden they concluded that these crystals are topological insulators with electrical conducting channels. The recent experiments at RWTH Aachen and combined calculations in Dresden have now proved this hypothesis.

A new semiconductor compound is bringing fresh momentum to the field of spintronics, an emerging breed of computing device that may lead to smaller, faster, less power-hungry electronics. 

Created from a unique low-symmetry crystal structure, the compound is the first to build spintronic properties into a material that's stable at room temperature and easily tailored to a variety of applications. It could eventually be used as the base material for spintronic processors and other devices, much like silicon is the base for electronic computing devices.

Spintronics use both the "on" or "off" electrical charge and the "up" or "down" magnetic spin of electrons to store information, whereas today's electronics use only electrical charge. Spin-based circuits can be smaller than charge-based circuits, enabling device makers to pack more of them onto a single processor. This is a key advantage, since traditional electronics are approaching their physical size limits.

"You can only make an electronic circuit so small before the charge of an electron becomes erratic," said Ferdinand Poudeu, assistant professor of materials science and engineering at the University of Michigan "But the spin of electrons remains stable at much smaller sizes, so spintronic devices open the door to a whole new generation of computing."

Spintronics can also retain data even after power is shut off, unlike today's microprocessors and computer memory. This may enable device makers to combine functions that require separate components in today's computing devices. For example, instead of using a processor to make calculations, RAM memory for primary storage and a hard drive for secondary storage, a single spintronic chip could handle all three functions, dramatically reducing the size and power consumption of computers.

But spintronic semiconductors require precise levels of both magnetism and conductivity. Researchers have struggled to create one that can be easily tuned to the levels required and that maintains its properties over a range of temperatures. Poudeu said that the root of the problem lies in the crystalline structure that makes up semiconductors. 

"Today's semiconductors are made of crystals with simple, symmetrical patterns, like a microscopic lattice that repeats over and over," he said. "We control the properties of those semiconductors by adding atoms of different elements to the holes in that lattice. For example, we can add bismuth to increase conductivity, or iron to increase magnetism.

"To make spintronic semiconductors, we need to add atoms of different sizes, and we need flexibility in where we place those atoms. But in most commonly used crystals, the holes are all similarly sized and regularly spaced. That gives us a very limited amount of control."

Researchers have been working for years to solve this problem by finding new ways to add atoms to commonly used crystalline structures. But Poudeu's team took a different approach, creating an entirely new crystal structure. They used a mixture of iron, bismuth and selenium to create a complex crystal that offers much greater flexibility. Their low-symmetry crystal has holes of varying size placed at varying distances in multiple, overlapping layers.

"Ordinarily, conductivity and magnetism are linked together, so you can't change one without affecting the other," said Juan Lopez, a doctoral student in materials science and engineering who worked on the project. "But this new compound changes that. It enables us to arrange atoms in a huge number of different combinations so that we can manipulate conductivity and magnetism independently. That level of control is going to open a whole new set of possibilities in spintronics."

Lopez said the project's cross-disciplinary team has brought a fresh perspective to the project, combining chemistry, crystallography and computer science to build a new solution to a problem that has vexed researchers for years.

"What I've really enjoyed about this project is that we've taken a clean-sheet approach," he said. "Our backgrounds have helped us think differently about spintronics and find a completely new solution to a relatively old problem. And we're gaining a better understanding of the fundamental science of crystallography as well."

So far, the team has only created and tested the new compound in powder form. The next step is to manufacture it in the thin film that would be required for a spintronic device. Lopez believes that this may be feasible within a year.

NSF announces newest awards for Material Research Science and Engineering Centers

Materials science and engineering research thrives in collaborative environments, and now we have 12 more examples of how the National Science Foundation (NSF) helps ensure creative, inclusive environments where progress can be made in this diverse scientific discipline.

NSF today announced awards for 12 Materials Research Science and Engineering Centers (MRSECs) for multidisciplinary work that covers all areas of material science, fostering active university, national laboratory, industrial and international collaboration with integral multidisciplinary education and outreach. MRSECs receive $56 million in NSF funding.

The centers support some of the world's best multi- and inter-disciplinary materials research and education addressing fundamental problems, such as developing new nanomaterials to build better artificial knee replacements and heart valves or developing 2-D materials that will likely transform supercomputing. While some research centers in other disciplines may have one specific focus or mission, the MRSECs serve primarily as a hub of collaboration where research interests can range more broadly, addressing several scientific questions or issues.

"These awards are representative of the exquisitely balanced and highly multidisciplinary research portfolio spanning all of the division-supported research areas," said Mary Galvin, director of the NSF Division of Materials Research. "These multidisciplinary awards, in particular, will promote areas such as next-generation quantum computing, electronics and photonics and bio- and soft-materials."

NSF's newest MRSEC at Columbia University will have two interdisciplinary research groups (IRGs) that build higher dimensional materials from lower dimensional structures and with unprecedented control. One of the research groups will study how 2-D materials interact to create new physical phenomena to potentially be integrated into electronic devices, and the other research group may establish a new type of periodic table by using molecular clusters to assemble materials, which could generate new electronic and magnetic materials of technological importance.

Columbia will lead the MRSEC and partner with City College of New York, Harvard University, Barnard College, the University of the Virgin Islands, Brookhaven National Laboratory, IBM and DuPont. The partners will work together to develop educational outreach activities for nearby K-12 schools.

The other 11 MRSEC awards, made to existing NSF MRSECs, also represent melting pots of cutting-edge materials science and engineering, and in most cases, the centers will take on new materials research and focus on education:

The Brandeis University MRSEC, studying bioinspired soft materials, startedin 2008, will add a second IRG. Employing fundamentally new approaches, the center ultimately could have significant societal impacts. The initial research group's discoveries may be useful for more targeted drug delivery systems in the future. The new IRG hopes to develop new materials for artificial muscles, self-pumping fluids and self-healing materials. This MRSEC runs a multi-level outreach and education program that includes exhibits at the Acton, Mass., Discovery Museum and a Research Experiences for Undergraduates program.

Starting in 1961 as a Materials Research Laboratory, the University of Chicago center became a MRSEC in 1994, supporting innovative research focused on investigating a fairly broad range of materials. The center's research is aimed at helping in design and synthesis of active materials that mimic behavior of living cells, which could have device applications such as self-propelled robotics.

Another focus is the development of artificial quantum coherent materials with tunable properties; this is important for future quantum information technologies. Goals include advancing applications in quantum sensing, fabricating materials for quantum information as well as creating the next generation of characterization tools for traditional materials. Through three IRGs, the center is a nexus for collaboration between Argonne National Laboratory, the University of Chicago and a Partnership for Research and Education in Materials at the City College of New York. Underserved area students benefit from MRSEC-sponsored after-school science clubs as just one part of its extensive outreach program.

University of Colorado at Boulder's Soft Materials Research Center will add a second IRG this year that proposes an exciting new area that will use "thiol-ene click chemistry" to develop inexpensive synthetic analogs of DNA. Rather than a specific single reaction, click chemistry aims to create products that follow examples in nature. In this case, the DNA analogs would offer a greater range of chemical properties than those exhibited by natural nucleic acids. The pioneering work is speculated to take molecular biology to the next level and will likely lead to a new field. The center already has a wide variety of outreach programs, including a family science show and a Pathways program that helps underrepresented high school students transition successfully to and through college.

An MRL since 1961, Harvard University's center became a MRSEC in 1994 and supports soft matter science through three IRGs. One of its IRGs aims to advance the theory of flow and mixing of viscoelastic materials in microfluidics, which would significantly advance 3D printing. Another of the IRGs could impact mechanical devices for prosthetics. One of its most well-known (and most popular) outreach programs is its Science and Cooking lecture series, featuring faculty and well-known chefs. The Harvard MRSEC is also developing special initiatives to bring returning veterans into STEM (science, technology, engineering and mathematics) fields.

The University of Minnesota MRSEC, originally awarded in 1998, is founded upon three IRGs: one whose advancements in basic science could provide new options for energy efficiency, including the use of superconductors, information storage and solid-state lighting; another that will work on a solvent-free process for producing nanocrystal-based thin films that would be environmentally and industrially appealing; and the other, whose work involves block copolymers that could impact myriad technologies, such as membranes for chemical separations, water purification and battery separators. Outreach includes--among other things--a new residential camp for Native American students.

Started as an MRL in 1961, Massachusetts Institute of Technology's (MIT) MRSECbecame a MRSEC in 1994 with three IRGs. The eventual societal benefits of the MRSEC research might be felt in diverse aspects of modern life including possible transformational impacts in communications and computation infrastructure, new physical and biological knowledge and materials relevant to biomedical applications. One of the IRGs will work to improve how synthetic gels mimic natural materials' properties, and another's focus on complex oxides could specifically impact development of future fuel cell technologies and information storage. The center offers a wide variety of educational outreach programs at all levels, including MIT Museum Second Fridays and an annual citywide Cambridge Science Festival.

Begun in 2002, the University of Nebraska Polarization and Spin Phenomena in Nanoferroic Structures MRSEC is likely to have a significant impact that results in energy-efficient electronic devices. Its IRG that will study non-linear, magnetoelectric effects in thin films could revolutionize certain segments of the electronics industry. The other IRG will likely impact low-power switches and logic electronic devices, which could lead to energy-efficient solid state electronics. Educational activities are varied and include research experience programs, a Conference for Undergraduate Women in Physical Sciences and a new "Bridge Program" that will partner with three minority-serving institutions of higher education.

The New York University MRSEC that began in 2008 adds a second IRG that will study designer molecular crystals that have potential applications in pharmaceuticals, organic electronics and coatings. Its initial IRG also works on improving materials for disruptive technologies, for example optical computing. Educational and outreach activities, such as a Scientific Frontiers Program, a Biobusthat delivers materials science lessons and teacher training on wheels and Science Video Vignettes that spark interest in STEM among thousands of NYC K-12 students, most from underrepresented and economically disadvantaged groups.

The Ohio State University Center for Emerging Materials, which has been a MRSEC since 2008, adds a third IRG and could impact spintronic, electronic and optoelectronic device development and even quantum information science. This new IRG, with research in non-linear spin transport, could lead to new spintronic devices such as low power consumption interconnects, spin-based information processing devices, spin amplifiers and spin logic/memories. Additionally, one of the other two IRGs' research may contribute to the design of magnetic memory devices and magnetic sensors. The other will study a new family of "chemically functionalizable" and "electronically tunable" 2D materials, which could assist in developing improved next-generation applications in opto-electronics and solid state electronics. One of this center's new educational outreach tactics will enhance its vibrant Research Experience for Undergraduates and Scientific Thinkers programs to more effectively widen the STEM pathway.

Started in 2000, the Penn State University Center for Nanoscale Science has four IRGs with potential impacts in several areas of science. The first IRG will continue its work to discover new metal oxide compounds that could have potential applications in several new technologies. Another IRG has potential to aid the design of new materials with bio-inspired functions. Another will study a new class of materials that could have bearing on energy conversion and energy conservation. The final IRG could help develop the next generation of fabrication methods. From smartphone software to hands-on materials science kits, the center reaches more than 100,000 museum-goers annually, and that is only a portion of its educational outreach.

The Princeton University Center for Complex Materials has existed since 1994 and is currently organized into three IRGs. One of the IRG's work will likely impact spintronics and quantum information technology. Another IRG could have impact on organic electronics, and the third IRG is likely to uncover interesting discoveries in fundamental aspects of quantum systems and thus impact our understanding of materials for quantum information technology. Again, this center too has a broad array of education projects, which only partially includes a rigorous three-week science camp and eight science fairs per year.

"The MRSEC centers provide leadership for the country concerning new materials and new materials phenomena that could ultimately address national needs, including sustainability and innovation," Gavin said. "We are especially excited about the international, industrial and national laboratories' collaborations that will give junior researchers in the centers experiences valuable to their lives as scientists and engineers."

More detailed and technical information is available for each of these centers on the NSF MRSEC website.

Michigan team tests radiation-resistant spintronic material, possibly enabling electronic devices that will work in harsh environments

A team of researchers from the University of Michigan and Western Michigan University is exploring new materials that could yield higher computational speeds and lower power consumption, even in harsh environments. 

Most modern electronic circuitry relies on controlling electronic charge within a circuit, but this control can easily be disrupted in the presence of radiation, interrupting information processing. Electronics that use spin-based logic, or spintronics, may offer an alternative that is robust even in radiation-filled environments.

Making a radiation-resistant spintronic device requires a material relevant for spintronic applications that can maintain its spin-dependence after it has been irradiated. In a paper published in the journal Applied Physics Letters, from AIP Publishing, the Michigan research team presents their results using bulk Si-doped n-GaAs exposed to proton radiation.

How Does Spintronics Work? 

Modern electronic devices use charges to transmit and store information, primarily based upon how many electrons are in one place or another. When a lot of them are at a given terminal, you can call that 'on.' If you have very few of them at the same terminal, you can call that 'off,' just like a light switch. This allows for binary logic depending on whether the terminal is 'on' or 'off.' Spintronics, at its simplest, uses the 'on/off' idea, but instead of counting the electrons, their spin is measured. 

"You can think of the spin of an electron as a tiny bar magnet with an arrow painted on it. If the arrow points up, we call that 'spin-up.' If it points down, we call that 'spin-down.' By using light, electric, or magnetic fields, we can manipulate, and measure, the spin direction," said researcher Brennan Pursley, who is the first author of the new study. 

While spintronics holds promise for faster and more efficient computation, researchers also want to know whether it would be useful in harsh environments. Currently, radioactivity is a major problem for electronic circuitry because it can scramble information and in the long term degrade electronic properties. For the short term effects, spintronics should be superior: radioactivity can change the quantity of charge in a circuit, but should not affect spin-polarized carriers. 

Studying spintronic materials required that the research team combine two well established fields: the study of spin dynamics and the study of radiation damage. Both tool sets are quite robust and have been around for decades but combining the two required sifting through the wealth of radiation damage research. "That was the most difficult aspect," explains Pursley. "It was an entirely new field for us with a variety of established techniques and terminology to learn. The key was to tackle it like any new project: ask a lot of questions, find a few good books or papers, and follow the citations."

Technically, what the Michigan team did was to measure the spin properties of n-GaAs as a function of radiation fluence using time-resolved Kerr rotation and photoluminescence spectroscopy. Results show that the spin lifetime and g-factor of bulk n-GaAs is largely unaffected by proton irradiation making it a candidate for further study for radiation-resistant spintronic devices. The team plans to study other spintronic materials and prototype devices after irradiation since the hybrid field of irradiated spintronics is wide open with plenty of questions to tackle.

Long term, knowledge of radiation effects on spintronic devices will aid in their engineering. A practical implementation would be processing on a communications satellite where without the protection of Earth's atmosphere, electronics can be damaged by harsh solar radiation. The theoretically achievable computation speeds and low power consumption could be combined with compact designs and relatively light shielding. This could make communications systems faster, longer-lived and cheaper to implement.

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