New results give information about phase transitions at the nanoscale.
nyone who has watched steam billow up from a boiling kettle or seen ice crystals form on a wet window in winter has observed what scientists call a phase transition.
Phase transitions — such as those between solids, liquids and gases — occur in all kinds of different substances, and they can happen rapidly or slowly. Scientists plan to use phase transitions to be able to control the electronic, structural or magnetic properties of different materials as they undergo these changes, such as for use in new types of computer memories.
“We’re able to zoom into a sample in terms of time and space in ways we have never been able to before.” — Youngjun Ahn, study author
In a new study, researchers have for the first time been able to look at a structural phase transition in minute detail on a very fast timescale. The scientists made X-ray “photographs” that are spaced less than one-tenth of 1 billionth of a second apart through a technique called nanodiffraction microscopy. “A typical video might play at 30 frames per second, so this is approximately a slow-motion video that can resolve dynamics that are extremely fast,” said Haidan Wen, a physicist at the U.S. Department of Energy’s (DOE) Argonne National Laboratory.
The ability to witness the evolution of material behavior with such precision in time and space has revealed unusual behaviors in certain materials that undergo a phase change, including many magnetic materials.
“We’re able to zoom into a sample in terms of time and space in ways we have never been able to before,” said Youngjun Ahn, the first author of the study. Ahn is a former graduate student intern at Argonne from the University of Wisconsin-Madison. For this work, he collaborated closely with Wen. “This method gives us a precise view of structural changes in our sample that are challenging to see with any other method,” Ahn said.
The study used the Hard X-Ray Nanoprobe operated by the Center for Nanoscale Materials (CNM) at the Advanced Photon Source (APS) at Argonne. The APS and CNM are DOE Office of Science user facilities.
In looking at phase transitions in an iron-rhodium compound, the researchers found a way to watch the structure of the compound change between two magnetic configurations. The change causes an expansion of the atomic network that is very small — but enough to have significant consequences for the magnetism.
Scientists can use the magnetic phases to create a new kind of magnetic storage that promises to be faster and more energy-efficient than conventional data storage. In all magnetic materials, manipulating phase transitions around the critical temperature at which they occur can provide the key to being able to flip an information-storing bit between a “1” and a “0”.
In order to fashion magnetic memories that are compact, scientists need to have a way to manipulate them precisely. One way to do that is with a local change of temperature.
By heating up a magnetic bit, scientists could potentially have a way to induce the reconfiguration that they use to encode information with less energy consumption, which is known as heat-assisted magnetic recording. “One of the things that’s very interesting about this particular material — iron-rhodium — is that it has a phase transition at a temperature that could be used for these kinds of applications,” said University of Wisconsin-Madison professor Paul Evans. “But in order to do the kinds of manipulations we’re interested in, we need a better ‘camera.’ That’s why using this newly developed technique to study it is important.”
“The key aspect of our experiment is that we are able to access the extremely small regions of space or quick moments in time with high precision that allows us to uncover nanoscale dynamics that has not been recognized before,’ added Wen, who conceived the work.
The upcoming upgrade to the APS will have significant implications for further experiments visualizing these kinds of phase transitions. “After the APS upgrade,” said Argonne X-ray scientist Martin Holt, “we expect to achieve higher spatial resolution, in particular, by exploiting the enhanced coherence of the X-ray beam. Our development of ultrafast time resolution within that type of X-ray microscopy is what helps us understand the causes of the types of effects we’re observing. This is a unique capability that the upgraded APS can offer.”
A paper based on the study, “X-ray nanodiffraction imaging reveals distinct nanoscopic dynamics of an ultrafast phase transition,” appeared in the May 6 issue of Proceedings of the National Academy of Sciences.
In addition to Ahn, Holt, Evans and Wen, other authors of the study include Argonne’s Mathew Cherukara, Zhonghou Cai, Michael Bartlein, Tao Zhou, Anthony DiChiara, Donald Walko, as well as Eric Fullerton of the University of California at San Diego.
The work was funded by DOE’s Office of Science (Office of Basic Energy Sciences).
About Argonne’s Center for Nanoscale Materials
The Center for Nanoscale Materials is one of the five DOE Nanoscale Science Research Centers, premier national user facilities for interdisciplinary research at the nanoscale supported by the DOE Office of Science. Together the NSRCs comprise a suite of complementary facilities that provide researchers with state-of-the-art capabilities to fabricate, process, characterize and model nanoscale materials, and constitute the largest infrastructure investment of the National Nanotechnology Initiative. The NSRCs are located at DOE’s Argonne, Brookhaven, Lawrence Berkeley, Oak Ridge, Sandia and Los Alamos National Laboratories. For more information about the DOE NSRCs, please visit https://science.osti.gov/User-Facilities/User-Facilities-at-a-Glance.
About the Advanced Photon Source
The U. S. Department of Energy Office of Science’s Advanced Photon Source (APS) at Argonne National Laboratory is one of the world’s most productive X-ray light source facilities. The APS provides high-brightness X-ray beams to a diverse community of researchers in materials science, chemistry, condensed matter physics, the life and environmental sciences, and applied research. These X-rays are ideally suited for explorations of materials and biological structures; elemental distribution; chemical, magnetic, electronic states; and a wide range of technologically important engineering systems from batteries to fuel injector sprays, all of which are the foundations of our nation’s economic, technological, and physical well-being. Each year, more than 5,000 researchers use the APS to produce over 2,000 publications detailing impactful discoveries, and solve more vital biological protein structures than users of any other X-ray light source research facility. APS scientists and engineers innovate technology that is at the heart of advancing accelerator and light-source operations. This includes the insertion devices that produce extreme-brightness X-rays prized by researchers, lenses that focus the X-rays down to a few nanometers, instrumentation that maximizes the way the X-rays interact with samples being studied, and software that gathers and manages the massive quantity of data resulting from discovery research at the APS.
This research used resources of the Advanced Photon Source, a U.S. DOE Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357.
Argonne National Laboratory seeks solutions to pressing national problems in science and technology. The nation’s first national laboratory, Argonne conducts leading-edge basic and applied scientific research in virtually every scientific discipline. Argonne researchers work closely with researchers from hundreds of companies, universities, and federal, state and municipal agencies to help them solve their specific problems, advance America’s scientific leadership and prepare the nation for a better future. With employees from more than 60 nations, Argonne is managed by UChicago Argonne, LLC for the U.S. Department of Energy’s Office of Science.
The U.S. Department of Energy’s Office of Science is the single largest supporter of basic research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time. For more information, visit https://energy.gov/science.
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