Program Highlights

nuggets 

Highlights:

Research and education highlights are brief and digestible summaries of recent significant research results or education activities, chosen for their potential interest to a broad audience.

 

Resent Research and Education Highlights

IRG1 highlight 2016

Detecting Magnetic Order when Magnetization is Absent

Junlei Wang and Christian Binek
Nebraska MRSEC

Antiferromagnets are magnetically ordered materials which lack the net magnetization known for ferromagnets. In an antiferromagnet, spins arrange in opposing sublattices with mutually compensating magnetization. Not unlike ferromagnets, antiferromagnets can have domains. In a simple case, the domains are differentiated through spin reversal. Identifying a specific antiferromagnetic domain is a notoriously difficult experimental problem.
Nebraska MRSEC researchers developed a magneto-optical table-top setup (Phys. Rev. Applied 5, 031001 (2016)) that allows detecting magnetic order in magnetoelectric antiferromagnets, such as chromia, which rotate the plane of polarization of transmitted light in response to electric fields. Probing with light of a specific wavelength allows determining the domain state from the sign of the rotation angle. In chromia, domain states can not only be detected but also selected through voltage. This property plays a key role in potential ultra-low power spintronic memory and logic devices. Advancing them requires investigation of antiferromagnetic domains. 

Picture: Schematics of the physical principle to discriminate two ordered states of a magnetoelectric antiferromagnet. In the presence of applied voltage, the polarization plane of linearly polarized light rotates in opposite directions when light is transmitted through the domains with reversed spins.

croconic acid

Room-Temperature Ferroelectricity in Croconic Acid Films

Axel Enders, Xiaoshan Xu, Alexei Gruverman, Xuanyuan Jiang, Haidong Lu,
Yuewei Yin, Xiaozhe Zhang, Zahra Ahmadi, and Paolo Costa
Nebraska MRSEC

Molecular ferroelectrics have the potential to become viable material alternatives to inorganic ferroelectrics. Unlike traditional oxide ferroelectrics, molecular ferroelectrics are structurally flexible, can be engineered at the molecular level, and can be assembled on nearly any surface, including flexible sheets and fabrics. The application of molecular ferroelectrics hinges, however, on the availability of strategies to fabricate thin films with defined structure and morphology on a large scale, which at the same time preserve their ferroelectric properties.
Nebraska MRSEC researchers have demonstrated for the first time the successful growth of a continuous nanometer thin film of a proton transfer ferroelectric organics, croconic acid, solvent-free from the vapor phase, while fully maintaining the material’s ferroelectric properties. The key to success has been the careful sublimation of croconic acid powder at temperatures that are far below the melting point. Ferroelectric testing of the films at room temperature shows a polydomain structure which can be manipulated locally, at the level of individual nanocrystals, by applying a voltage pulse to the tip of an atomic force microscope. The application of the solvent-free growth protocol to molecular ferroelectric thin films is scalable and may be key to the development of flexible and bendable ferroelectric thin films for electronics applications.

Picture: Ferroelectric polarization map of a selected region of a 30 nm thin film of croconic acid measured before (top) and after (bottom) local application of a voltage pulse.

scienceslam

Science Slams: The Future of Science Communication

Axel Enders and Jocelyn Bosley
Nebraska MRSEC

Held for the first time on March 16, 2016, on the University of Nebraska-Lincoln (UNL) campus, Science Slams is a new signature activity for the Nebraska MRSEC education and outreach program, and a first-of-its-kind event in the United States. The goal of Science Slams is to encourage undergraduate and graduate students to widen their focus beyond the results of their immediate research, making these results understandable and meaningful to a broad audience in a concise and engaging way.
The varied academic backgrounds of the speakers and audience members forced the speakers, or slammers, to discuss their work in ways that would communicate the excitement of their research to a diverse audience. The audience had an all-important role to play in deciding the outcome of the Slam, with their votes determining the winner, who received a cash prize.
As a novel form of science communication, Science Slams provide a platform for students to develop new communication strategies while also breaking down barriers among scientific disciplines. Nebraska MRSEC is taking the lead in efforts to further grow Science Slams into a nationwide phenomenon. This event has already attracted national attention, including an article in Popular Science, which can be found at http://www.popsci.com/science-slams-could-be-future-communicating-research. More details can be found at http://mrsec.unl.edu/science-slam, and videos of all the finalists’ presentations are available on the YouTube channel

Picture: Alice MillerMacPhee of the UNL Department of Sociology recreates her journey from passionate activist to data-driven social scientist in her Science Slam talk.

seed project

Nucleation Control of Conjugated Polymers

Ramin Hosseinabad and Lucia Fernandez-Ballester
Nebraska MRSEC

Rafael Verduzco
Rice University

Conjugated polymers are large organic macromolecules that have alternating single and double bonds along the backbone, which confer remarkable optical and electronic properties. These materials are attractive for applications in solar cells, field-effect transistors, and light-emitting diodes because of their low cost and easy processability. Regulating the crystallization of conjugated polymers is key to optimizing their properties. Nucleation is the first step in the formation of crystallites and its control allows rational design of materials with desired morphology and properties. However, the basic mechanism of nucleation and crystallization of conjugated polymers remains obscure and must therefore be thoroughly explored.
Nebraska MRSEC researchers in collaboration with Rice University are exploring the melt crystallization and self-seeding behavior of Poly(3-Hexylthiophene) (P3HT) – a conjugated polymer with significant charge-carrier mobility. Results show that populations of P3HT crystallites with different stabilities can be obtained by using well-defined crystallization temperatures, and that self-seeding thermal protocols can effectively be used to increase the number of nuclei that emerge in the melt under fixed conditions—thus increasing kinetics of crystallization and influencing the final morphology.  Initial findings indicate that imposition of a well-defined flow can impact the location and geometry of nucleation. This research provides new insights on the relationship between processing conditions, nucleation and crystallization, and morphology, leading towards rational design and optimal control of properties of conjugated polymers.

Picture: Oriented crystallization of conjugated polymer P3HT.  Flow direction is indicated by the arrow.

IRG1

Elucidating Single-ion Magnetic Anisotropy in LuFeO3 

Xiaoshan Xu, Peter A. Dowben, and Evgeny Y. Tsymbal, Shi Cao, Xiaozhe Zhang, Tula R Paudel, Kishan Sinha, and Xuanyuan Jiang
Nebraska MRSEC

Multiferroic materials carry spontaneous electric and magnetic dipole moments simultaneously which makes them promising for the application in energy efficient information technologies. This is due to the coupling between the electric and magnetic dipole moments, which may enable voltage controlled switching of the magnetization. Lutetium ferrite, LuFeO3, is one of the multiferroic materials whose spontaneous magnetic moment relies on its preferred orientation on the atomic site. This property, known as the single-ion magnetic anisotropy, is difficult to elucidate due to a small energy scale controlling its behavior.
Nebraska MRSEC researchers have revealed the origin of the single-ion magnetic anisotropy in LuFeO3. Using collaborative efforts in thin film growth, x-ray absorption spectroscopy, and density functional theory, they demonstrated that the local symmetry of the iron ion (Fe3+) sites determines this property. They found that for both hexagonal and orthorhombic LuFeO3 (shown in the figure) the small distortion of the crystal structure changes the local symmetry of the Fe3+ ions and thus alters the orientation of their magnetic moments.  This result is important because it suggests a route for tuning magnetism in multiferroic materials, like LuFeO3, by the fine adjustment of their crystal structures, as well as a route in coupling the electricity and magnetism via structural distortions.

Figure: Crystal structures of hexagonal (left) and orthorhombic (right) LuFeO3. Arrows indicate orientations of the magnetic moments on the Fe sites.

shared facilities

Nebraska Nanoscale Facility

Christian Binek
Nebraska MRSEC

Nebraska Materials Research Science and Engineering Center (MRSEC) is fortunate to be complemented by a state-of-the-art scientific infrastructure at the University of Nebraska-Lincoln (UNL). A beacon of this infrastructure is the Nebraska Center for Materials and Nanoscience (NCMN). It has been established in 1988 to support UNL’s research and education in nanoscale materials for magnetic and information technologies, electronics and sensors, energy systems and sustainable manufacturing. NCMN serves chemists, engineers, materials scientists, and physicists many of whom are Nebraska MRSEC researchers. NCMN has a proven track-record of stimulating interdisciplinary research.
Recently, NCMN’s capabilities have been substantially leveraged via a $3.5 million grant from the National Science Foundation (NSF). The funding allowed to establish the Nebraska Nanoscale Facility (NNF) as a regional center of excellence in nanoscience and nanotechnology. NNF is one of 16 centers created under the NSF’s National Nanotechnology Coordinated Infrastructure, designed to advance the nation’s nanoscience research by expanding the equipment and service capabilities of universities and industries. The NNF infrastructure is housed in the Voelte-Keegan Nanoscience Research Center which guarantees maximum leverage of MRSEC shared facilities by providing lab space, support through NNF funded technicians and facilities maintenance not possible by MRSEC resources alone.

Picture: Volte-Keegan Nanoscience Research Center which houses Nebraska Nanoscale Facility infrastructure.

highlight 2016

Nebraska MRSEC Strengthens International Partnerships 

Tula Paudel and Evgeny Tsymbal
Nebraska MRSEC

Nebraska MRSEC, known as P-SPINS, has a broad network of international partners, which complement and strengthen its research capabilities. Partnerships with international institutions provide a source for new ideas, allow access to complementary facilities, enhance possibilities to recruit the best students and faculty, and involve opportunities for students to interact with international collaborators.  
Recently Nebraska MRSEC researchers were involved in a collaborative study spanning three continents and the pages of journal Science (Science 349, 716 (2015)). This study discovered that a compound called lanthanum manganite features no magnetism when it is grown up to five atoms thick. Adding a sixth atomic layer, however, drives the material to become magnetic. The emergence of magnetism is induced by a restructuring of the compound’s electrons, which migrate from the top of the film to its bottom. These electrons then become confined between the film and the substrate on which it is grown ultimately producing magnetism. Being able to control and manipulate magnetism at the ultimate atomic scale may be important for novel device applications. This work was led by scientists from the Netherlands-based University of Twente and the National University of Singapore, with researchers from Stanford University and the Ireland-based Trinity College also contributing. 

Picture: Abrupt appearance of magnetism in lanthanum manganite thin films, when their thickness is increased from 5 atomic layers (left) to 6 atomic layers (right). Arrows indicate magnetic moments on manganese atoms.

edu 2016

P-SPINS Research in K-6 Science Curriculum Development

Krista Adams and Jocelyn Bosley
Nebraska MRSEC

Collaboration between researchers of Nebraska MRSEC and pre-service elementary science teachers is aimed at connecting MRSEC research in materials and nanoscience with the science curriculum at elementary schools in Lincoln, NE. Through this collaboration, pre-service elementary science teachers are introduced to basic concepts in nanoscience through a combination of targeted activities, with the premise that a better understanding of scientific research will allow teachers to feel more confident teaching science to their students, spurring curiosity about the physical sciences and inspiring the next generation of materials scientists.
MRSEC Investigator Krista Adams and MRSEC Education/Outreach Coordinator Jocelyn Bosley have spearheaded these activities, which included tours of MRSEC labs for students in Adams’ Elementary Science Methods course, demonstrations of concepts and methods in nanoscience, and the development of lesson plans to implement in after-school clubs at elementary schools. A highlight was a workshop in which MRSEC undergraduate researchers helped Adams’ students to refine the scientific content of their lesson plans. Results from the first iteration of this collaboration are being used to develop instructional guides that will enable future teachers to implement similar strategies in their own classrooms. These lessons were chronicled on the UNL PSPINS vlog and can be found here: https://youtu.be/MYnwPJi4L_0.

Picture: MRSEC undergraduate Celeste Labedz (middle) serves as a peer mentor for Adams’ pre-service elementary science teachers.

 

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