The Wisconsin MRSEC has created thin films of a fascinating magnetic material, Pr2Ir2O7, in which the magnetic moments are frustrated: No matter how they are arranged, some of the moments are always fighting to change their direction, like two bar magnets with their north poles shoved together. Frustration creates a rich landscape for discovery and manipulation of new magnetic effects and of electronic phenomena linked to magnetism.
Using physical vapor deposition, researchers produced glassy films that are smooth and uniform, but which also have the molecules aligned with one another and organized in layers. This added structure could make the glass more efficient for conductors and expand the range of materials that can be used in future organic electronics. The colorful images in the figure show measurements using synchrotron x-rays that contrast the disordered starting material and the ordered glass.
IRG 1 showed how the atoms around the defects can restrict their ability to jump between configurations and how defects can talk to each other via sound waves. Both phenomena keep the defects from interfering with sound waves allowing the waves to travel long distances.
The Wisconsin MRSEC is committed to being a leader in Open Science, which shares data in digital forms following FAIR1 principles. As part of these efforts the Center has developed a new web site, a best practices guide, and held informational events. This year the Center launched the first Wisconsin MRSEC Excellence in Open Science Prize. The winner was graduate student Bradley Dallin2 for his work on molecules interacting with water, with potential applications from understanding human blood to protein folding diseases like Alzheimer’s. Bradley shared his results in papers, but also shared all his simulations and tools in an open accessible format for the community, increasing the impact of his work.
Researchers at the Wisconsin MRSEC have developed a new instrument using very bright synchrotron x-ray beams to watch nanoscale crystals as they grow. The system has a unique design that allows the crystals to grow in vacuum while keeping the x-ray lenses and the x-ray beam in air but bringing them very close to the crystal. Wisconsin MRSEC researchers are using this new instrument to learn about solid phase epitaxy, a process based on the growth of ordered crystals from a disordered amorphous solid, which is capable of creating new materials for applications in electronics, optics, sensors, and quantum information.
The Wisconsin MRSEC has developed machine learning techniques that enable the design of new toxin sensors using liquid crystal droplets that respond to the presence of different bacterial toxins and at extremely low concentrations by changing shape and appearance. Machine learning enables computers to automatically analyze the droplet responses to measure toxin concentration and type automatically at high accuracy. More generally, these results demonstrate that the machine learning approach can quickly extract valuable information from complex datasets.
The Wisconsin MRSEC is developing an ultrafast direct electron camera for use on a scanning transmission electron microscope (STEM) in its Shared Instrument Facilities. One application of the camera will be experiments to map strains – tiny variations in the distance between atoms – inside materials caused by defects in the crystal lattice or interfaces between two different materials. The MRSEC acquired an existing, slower camera to support technique development before the new camera arrives. An example strain map is shown to the right. The gray-scale image is a small Nb particle formed inside a larger Zr crystal. The color image shows the rotation of the Zr lattice caused by the interface between the two materials. Higher sensitivity maps covering larger areas with more points will be possible with the new camera.
Bacteria communicate via molecular signals that they produce in high concentrations. Bacterial communication promotes the formation of biofilms that can be harmful to humans and costly to industry. We have shown that collections of individual bacterial signaling molecules interact in water to form soft materials (“self-assemble”) with spherical, layered, or cylindrical structures. Simulation images showing the formation of a spherical structure (“micelle”) are shown with corresponding experimental images.
Heusler compounds are promising materials for next generation devices for direct conversion of heat to electricity (thermoelectricity) and for magnetic computer memory. Performance in these applications depends sensitively on the arrangement of the atoms and the behavior of electrons, both of which are hard to predict and harder to control for Heuslers. We have grown thin films of FeVSb, a new Heusler compound, using molecular beam epitaxy, a kind of spray painting with “cans” of different atoms. The top picture is an electron microscope image showing the arrangement of the Fe, V, and Sb as different size dots. On the right, the image shows the material we want, FeVSb. On the left, there is a completely new, unexpected material, Fe2VSb, which is a new kind of magnet.
Not all members of our community have the time or resources to attend science outreach events. To reach some of those people, the Wisconsin MRSEC conducts its engaging, hands-on science activities to a local food pantry. Customers can wait up to 90 minutes at the food pantry, providing ample time for educational activities for kids, their parents, and other curious adult visitors. By bringing science and engineering activities to the food pantry, the Wisconsin MRSEC forms connections with and helps inspire a new, diverse audience composed entirely of economically disadvantaged members of the community.