8 ADVANCED MATERIALS & PROCESSES | JULY/AUGUST 2023 A critical step of the analysis was simulating the magnetic fields within the iron arsenide sample, for which the team wrote new software called Magnstem. The program allowed the scientists to add magnetic effects specific to their material and study its impact on electron beam patterns. By combining 4D-STEM with Magnstem simulations, researchers resolved magnetic order down to 6 angstroms. illinois.edu. TWEAKING THERMAL CONDUCTIVITY IN REAL TIME Researchers led by two teams at the University of Minnesota Twin Cities (U of M) discovered a new method to tune the thermal conductivity of materials to control heat flow in real time. They report their tuning range is the highest ever recorded among one-step processes in the field, and could enable development of more energy-efficient electronic devices. Typically, the thermal conductivity of a material is a constant value. Yet the U of M scientists discovered a simple process to tune this value in lanthanum strontium cobaltite, a material often used in fuel cells. Just as a switch controls electricity flow to a light bulb, the new method provides a way to turn heat flow on and off in devices. The materials synthesis team fabricated the lanthanum strontium cobaltite devices using electrolyte gating, in which ions are driven to the material’s surface. This allowed TESTING | CHARACTERIZATION IMAGING MAGNETISM IN ANGSTROMS Researchers at the University of Illinois Urbana-Champaign developed a new electron microscopy technique that can resolve magnetic behavior on the scale of angstroms. They then used this method to fully resolve the antiferromagnetic order in iron arsenide for the first time. “The best techniques before now have achieved resolutions of a few nanometers. We have vastly exceeded that record,” says Professor Pinshane Huang. To achieve the higher resolution, the team used 4D scanning transmission electron microscopy (STEM). While standard STEM techniques record drops in the electron beam’s intensity as it interacts with the material, 4D-STEM captures full 2D scattering patterns as the beam scans along the two directions of the material’s surface. These data allowed the scientists to search the full beam patterns for the more intricate signals of atomic antiferromagnetism. Triangular holes make this material more likely to crack from left to right. Courtesy of N.R. Brodnik et al./Phys. Rev. Lett. Researchers at The University of Tokyo studied the flow of thermal energy in purified graphite ribbons and showed that heat can move more like a liquid under certain conditions, rather than diffusing randomly. The discovery could lead to more efficient heat removal from electronic devices. tinyurl.com/bddmtdtm. D-STEM performed on a sample of iron arsenide. Courtesy of Grainger College of Engineering at the University of Illinois Urbana-Champaign. A research team led by scientists from Ohio University, Athens, and Argonne National Laboratory, Lemont, Ill., report taking the world’s first x-ray signature of just one atom. This pioneering achievement, funded by the DOE, could revolutionize the way scientists detect materials. tinyurl.com/3wn4x83e. BRIEFS
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