Directed explosive emulsification propels ferromagnetic liquid droplets

Applying a DC electric field to an interfacial assembly of charged nanoparticle–surfactants allows for oversaturating the liquid-liquid interface. This work demonstrates that the stored Coulomb energy can be released on demand to steer and propel droplets at a specific velocity in a well-defined direction. The latter originates from the ballistic ejection of thousands of charged microdroplets from the surface of the parent droplet where the symmetry breaking of the interfacial assembly dictates the directionality of motion. The propulsion is autonomous, repeatable, and agnostic to the chemical composition of the nanoparticles. This mechanism of droplet propulsion opens a new avenue to advance soft microrobotics, create new types of active matter, and introduce new vehicles for compartmentalized delivery.

This work was carried out in collaboration with Thomas P. Russell (Berkeley Lab) and Ahmad K. Omar (UC Berkeley).

The original work was published in Adv. Mater. X, 2310435 (2024) 🔗

START SMART scheduled to launch in February

START SMART provides experiential learning to foster the curiosity and engagement of high school students in the field of science by integration with art. The program is designed to transform science education by demystifying the mathematics and physical principles through the creation of art.

The February workshops will offer opportunities to learn about physical principles, complete hands-on art projects, and model what is seen through the use of mathematics. We will provide an inside perspective on why you should choose physics and its relevance today.

START SMART is an outreach program envisioned, developed, and organized by our group and supported by the National Science Foundation under grant no. 2203933 and the UNL Collage of Arts and Sciences.

Colloquium on alternate career paths for Physics Ph.D.

Robert Streubel gives a physics colloquium at UNL dedicated to career opportunities for physics students in the age of AI and quantum materials. Inspired by the Science Outside the Lab workshops for graduate students and faculty, organized by the Arizona State University, he focuses on career paths for STEM-educated personnel in non-science and non-tech sectors. This includes consultant in private or non-profit companies or for government agencies or congress, clerking, and editor/program manager of journals and funding agencies.

More information about the Science outside the lab workshop can be found here.

If you are interested in a career in science policy, check out AAAS science and technology policy fellowships that place you (as U.S. citizen) in the executive, legislative, or judicial branch of the U.S. government. And for non-U.S. citizens: check out partner societies.

Phase contrast imaging of non‐collinear spin textures with Lorentz microscopy

Phase contrast imaging with x-rays and electrons provides enhanced spatial resolution and sensitivity to spin and charge distributions. Off-axis and in-line electron holography have become essential and powerful tools to visualized non-collinear spin textures in solid-state materials. Recent instrumentation developments and advances in phase retrieval algorithms have laid the foundation to study spatial and temporal variations of spin and charge distributions in magnetic and quantum materials at cryogenic temperatures. This invited article derives the theory of phase contrast imaging with in-line electron holography and gives a quantitative comparison between non-iterative and iterative phase retrieval algorithms. It specifically showcases the strength of exit wave reconstruction to disentangle structural and magnetic features enabling a correlation between structural defects and the magnetization.

The original work was published in J. Mater. Res. 38, 4977 (2023). 🔗

It is featured as a cover art. 🔗

Kerr microscope brings back nostalgia

More than thirteen years ago, Robert Streubel started his academic research as a Diplom student at the Dresden University of Technology working in parts at the Leibniz Institute for Solid State and Materials Research Dresden. In collaboration with Rudi Schaefer, he learned to become fascinated with magneto-optical Kerr effect microscopy and its application to magnetism research in planar and curved geometries and in-equilibrium and out-of-equilibrium.

Now, we are thrilled to have our own full-field Kerr microscope, which we can use for education purposes and basic sciences research. It perfectly complements our experimental capabilities.

Many thanks to Rudi Schaefer (Evico Magnetics) for development, installation, and training.

Angelea Arnett joins as undergraduate research assistant

We are excited to welcome Angelea to our group! Angelea has been and will continue to work with Herman Batelaan (experimental atomic, molecular, and optical physics). In addition, she will explore condensed matter physics with us.

Robert Streubel helps BES evaluate research programs at Argonne National Laboratory

Research programs at national laboratories of the U.S. Department of Energy undergo regular merit evaluations. This process includes mail-in and on-site reviews from national and international experts who, upon invitation, assess performance and potential of current and future research programs.

As the only non-tenured scientist, Robert Streubel had the honor to serve as one of eighteen reviewers for the Argonne National Laboratory triennial on-site lab review to recommend funding for the next three years to the U.S. Department of Energy, Basic Energy Sciences, Materials Sciences and Engineering Division.

Our first last-author paper

In pursuit of high-frequency oscillators and resonators for microelectronics, we investigate ferromagnetic resonators synthesized by metal-organic decomposition epitaxy. The quality factor for out-of-plane and in-plane resonances approaches 600 and 1000, respectively, at room temperature and 40 GHz. These values increase with temperature and are 100 times larger than those offered by commercial devices based on complementary metal-oxide semiconductor voltage-controlled oscillators at comparable production costs. This leap in performance is the reason why current iPhone generations use the same material.

This work was carried out in collaboration with Allen Sweet (Vida Products), Paul Ashby (Berkeley Lab), and Mathias Schubert (UNL).

The original work was published in J. Phys.: Condens. Matter 35, 485801 (2023). 🔗

Omar Taha and Narmada Wickramasinghe join as Ph.D. graduate student

We are excited to welcome Narmada and Omar to our group! Both are first-year graduate students in the Physics department and awardees of the David J. Sellmyer fellowship.

Elaine Yu joins as high school intern

We are excited to welcome Elaine to our group! Elaine was selected from Lincoln high school students to experience academic research.

More information about the Nebraska Center for Materials and Nanoscience STEM Summer High School Internship can be found here.

Robert Streubel visits D.C. to experience science outside the lab

Have you ever wondered how science, money, and interests influence far-reaching decisions and policies and affect everyday life and our future? The Science outside the lab is an excellent opportunity to experience this first-hand in Washington, D.C. Robert and twelve other university faculty from across the United States visited the U.S. Court of Appeals for the Federal Circuit, the National Nanotechnology Coordination Office, the Environmental Protection Agency, the National Academies of Science, Engineering, and Medicine, Senate staffer, and SRI International to talk about these matters and how science graduate students can become part of this machinery. The breadth and pace at which scientific data needs to be acquired, digested, analyzed, and articulated to inform science policy, national security, and intellectual properties is amazing.

The three-day workshop was organized by the Arizona State University and is the first faculty-oriented Science outside the lab. It built on twenty years of experience, success, and networks of the graduate-student-centered programs which have been supported by the National Nanotechnology Coordinated Infrastructure and the National Science Foundation.

More information about Science outside the lab can be found here.

If you are interested, check out AAAS science and technology policy fellowships that place you (as U.S. citizen) in the executive, legislative, or judicial branch of the U.S. government. And for non-U.S. citizens: check out partner societies.

CAS awards research impact and engagement grant: START SMART

The College of Arts and Science awards a one-year outreach and engagement grant to kickstart our outreach program - Science Turns into ART at the Sheldon Museum of ART (START SMART) - to spark interest in physical sciences among high school juniors and seniors. In the scope of UNL's Upward Bound and Upward Bound Math/Science TRIO programs, we will offer workshops concerning the crafting of instruments (different kinds and sizes of harmonographs), numerical modeling, and understanding of the underlying physical mechanisms.

Check it out. 🔗

Bryce Herrington, Amir Tarkian, and Ruthi Zielinski receive Undergraduate Creativity And Research Experience Award

Bryce, Amir, and Ruthi receive UNL's Undergraduate Creativity And Research Experience Awards. It is the first award for Amir and the third consecutive year for Bryce and Ruthi. Amir and Bryce will jointly study magnetic properties of soft-magnetic amorphous materials. Ruthi will investigate electronic transport in boron carbide films.

More information about UNL's Undergraduate Creativity And Research Experience Award can be found here.

Bryce Herrington receives Darrell J. Nelson Summer Undergraduate Internship in Energy Sciences Research

Our warmest congratulations to Bryce for being, once again, among the eight awardees from Nebraska to receive the prestigious Darrell J. Nelson Summer Undergraduate Internship in Energy Sciences Research. Bryce will investigate the magnetic and electronic transport properties of Fe(qsal)₂-TCNQ molecular magnets for prospective applications in non-volatile memory devices. The fellowship is bestowed by the Nebraska Center for Energy Sciences Research (NCESR) and valued at $6,000.

This research will commence his Honors thesis.

More information about NCESR can be found here.

Ferromagnetic liquid droplets have a blast

Oversaturation of surfactants at liquid–liquid interfaces causes an interfacial instability and the continued generation and diffusive spread of microdroplets. This work demonstrates the versatile use of ferromagnetic liquid droplets with superparamagnetic nanoparticle surfactants to transform the diffusive Brownian motion into directed propulsion. The spontaneous emulsification of superparamagnetic nanoparticles can be suppressed by an external magnetic field associated with a sizable reduction in the interfacial tension. Rapid removal of the field yields an explosive ejection of a plume of microdroplets from the surface, thereby reducing the areal density of the surfactants. Our results uncover an efficient energy storage and release process appealing to the controlled and directed delivery of chemicals and remotely controlled soft microrobots.

This work was carried out in collaboration with Thomas P. Russell (Berkeley Lab) and Ahmad K. Omar (UC Berkeley).

The original work was published in Adv. Funct. Mater. 33, 2213844 (2023). 🔗

It is featured as a cover art. 🔗

UNL revision grant

The Office of Research & Economic Development at UNL awards a revision grant to strengthen our research activities in topological magnetism in thin films consisting of transition metals, metalloids, and rare-earth elements.

2023 Emerging Investigators named by Nanoscale

Robert Streubel is recognized as an Emerging Investigator by the Royal Society of Chemistry’s Nanoscale. His special issue contribution "Electronic structure of cobalt valence tautomeric molecules in different environments" concerns the effect of creating an interface between a semiconducting polymer film and a local-moment valence tautomeric complex. This study leverages various spectroscopies and ab-initio calculations to identify electronic orbitals in valence tautomeric films with similar coordination. Slight modifications to the ligand groups reveal the possibility to engineer a spin-polarized local-moment-weighted orbital that spans the entire molecular plane, is optically active, and holds promise of a large magnetoresistance appealing to future molecular microelectronics.

This work was carried out in collaboration with Peter Dowben, Rebecca Lai (both UNL), Talat Rahman (UCF), Michael Shatruk (FSU), Ruihua Cheng (IUPUI), and Alpha N'Diaye (Berkeley Lab).

The original work was published in Nanoscale 15, 2044 (2023) 🔗 as part of their 2023 Emerging Investigators themed collection.

It is featured as a cover art.

Nhat Nguyen graduates with a major in physics and biochemistry

Congratulations to Nhat Nguyen who graduated in physics and biochemistry from the University of Nebraska-Lincoln. We wish him all the best for his future scientific career starting at the Texas A&M University (Biochemistry & Molecular Biophysics).

Recent advances in the field of tubular magnetic geometries

Within the last two decades, the field of 3D nano magnetism and curvilinear magnetism has evolved into a vital research field with an ever-growning community. Originating from theoretical works on tubular geometries, experimental efforts have been devoted to synthesizing 3D nano structures and visualizing the magnetization vector field. The creation of an analytical unified framework further boosted interest owing to curvature-driven local inversion symmetry breaking and vector spin exchange (Dzyaloshinskii–Moriya interaction). The latter favor chiral topological magnetic states of interest to both basic and applied sciences.

Our book chapter concerns recent theoretical and experimental advances in the study of tubular magnetic geometries and is co-authored by Pedro Landeros (Universidad Tecnica Federico Santa María, Chile), Jorge A. Otalora (Universidad Catolica del Norte, Chile), and Attila Kakay (Helmholtz-Zentrum Dresden - Rossendorf, Germany).

The book chapter was published in Denys Makarov and Denis D. Sheka (Eds.): Curvilinear Micromagnetism, 163-213, Springer (2022). 🔗

Amir Tarkian joins as undergraduate research assistant

Great start into the new academic year: Amir stays on as an undergraduate research assistant and will major in computer science and physics. We are intrigued to see how you will leverage your education for advanced data analysis.

Robert Streubel joins EQUATE as senior investigator

We are excited to have become the most recent addition to Nebraska's EQUATE program. Our expertise in x-ray absorption spectroscopies, x-ray and electron microscopies, magnetometry, electronic transport, and ferromagnetic resonance spectroscopy will boost UNL's research efforts in semiconducting organic and inorganic magnetic materials.

The RII Track-1: Emergent Quantum Materials and Technologies (EQUATE) program is sponsored by the National Science Foundation/EPSCoR to establish the state of Nebraska and UNL specifically as a center for future quantum materials and quantum information sciences.

More information about Nebraska's RII Track-1: Emergent Quantum Materials and Technologies (EQUATE) program can be found here.

NSF awards research grant on magnetic order in disordered dipolar nanostructures

The National Science Foundation, Division of Materials Research awards a three-year-long research grant to study magnetic order in disordered dipolar nanostructures, such as superparamagnetic nanoparticles and nanodisk arrays. It is our first official NSF grant and we are extremely excited to work on this project.

The grant builds on long-standing, fruitful collaborations with Tom Russell (UMass Amherst, LBL) and Jianwei Miao (UCLA).

Amir Tarkian joins as high school intern

We are excited to welcome Amir to our group! Amir was selected from Lincoln high school students to experience academic research before joining UNL in autumn.

More information about the Nebraska Center for Materials and Nanoscience STEM Summer High School Internship can be found here.

Bryce Herrington receives the Undergraduate Merit Award for Academic Performance in Physics

All the hard work pays off for Bryce. He receives the 2022 Undergraduate Merit Award for Academic Performance in the department of Physics and Astronomy. Congratulations for this well-deserved recognition!

Nhat Nguyen joins as undergraduate research assistant

Welcome to our group, Nhat! We are psyched to have you on-board. Nhat will assist us in identifying magnetization relaxation processes in perpendicular magnetized films with different pinning site density using our magneto-optical Kerr setup.

Ruthi Zielinski and Bryce Herrington receive Darrell J. Nelson Summer Undergraduate Internship in Energy Sciences Research

Congratulations to Ruthi and Bryce for being among the eight awardees from Nebraska to receive the prestigious Darrell J. Nelson Summer Undergraduate Internship in Energy Sciences Research. Ruthi will conduct electronic transport measurements on boron carbide films in pursuit of realizing boron carbide-based solid-state thermal neutron detectors. Bryce will investigate ferromagnetic resonances in yttrium iron garnet films for prospective applications in 5G cellular communication. The fellowship is bestowed by the Nebraska Center for Energy Sciences Research (NCESR) and valued at $5,000.

More information about NCESR can be found here.

Ruthi Zielinski and Bryce Herrington receive Undergraduate Creativity And Research Experience Award

Congratulations Ruthi and Bryce for securing a second time UNL's Undergraduate Creativity And Research Experience Awards. Their team project concerns the structural and magnetic properties of low-spin damping materials fabricated by metal-organic decomposition epitaxy.

More information about UNL's Undergraduate Creativity And Research Experience Award can be found here.

Mohammad Zaid Zaz joins as Ph.D. graduate student

We are excited to welcome Zaid to the group! Zaid is a first-year graduate student in the Physics department and our first official graduate student at UNL. Zaid will work on electrical and magnetic properties of molecular magnets, including band structure and ferromagnetic resonances and strengthen our collaboration with Peter Dowben (UNL).

Dynamical effects and critical field in spin-crossover molecules

Electronic circuit elements based on spin-crossover molecular films may some day transform microelectronics as they allow for ultra-fast switching between high-spin and low-spin state with on and off resistance differing multiple orders of magnitude. To date, little is known about spin-orbit coupling governing physical properties. Our recent publication confirms a non-vanishing orbital moment indicating spin-orbit coupling between neighboring molecules, which is particularly interesting for resonators and coherent elements.

This work was led by Peter Dowben (UNL) and carried out in close collaboration with Michael Shatruk (FSU), Ruihua Cheng (IUPUI), John Freeland (ANL), Vivien Zapf (Los Alamos), Alpha N'Diaye and Padraic Shafer (Berkeley Lab).

The original work was published in Chem. Commun. 58, 661 (2022). 🔗

Archit Dhingra selected as recipient of an Advanced Light Source Collaborative Postdoctoral Fellowship

Following an extraordinarily productive Ph.D., Archit got selected in the first cohort of the Spring 2022 Postdoctoral Fellowship Program of the Advanced Light Source, a national user facility of the U.S. Department of Energy located in the San Francisco Bay Area. The goal of this fellowship is to initiate the search for spin-crossover molecules to realize a scalable quantum device. The Advanced Light Source Collaborative Postdoctoral Fellowship program provides challenging opportunities to conduct collaborative research and instrument development leveraging advanced synchrotron radiation tools. It is valued at $30,000.

More information about the Collaborative Postdoctoral Fellowship can be found here.

Experimental evidence of curvature-driven DMI in nanospheres

Curvature-induced inversion symmetry breaking and associated modifications to magnetic exchange interactions have been extensively studied theoretically. Numerous research groups predicted the formation of chiral spin textures and topological states. Our recent publication gives the first experimental evidence of these predictions. Ab-initio calculations, magneto-transport, and x-ray absorption spectroscopy reveal non-magnetic Co-Si nanospheres whose surface magnetization likely forms topological spin textures.

This work was led by Ralph Skomski and David J. Sellmyer (UNL) and carried out in collaboration with Alpha N'Diaye and Padraic Shafer (Berkeley Lab).

The original work was published in Phys. Rev. Materials 5, 124418 (2021). 🔗

DOE BES report: Research opportunities in the physical sciences enabled by cryogenic electron microscopy

The U.S. Department of Energy, Office of Basic Energy Sciences releases roundtable report on research opportunities in the physical sciences enabled by cryogenic electron microscopy. The report, co-written by Robert Streubel, discusses opportunities and challenges in quantum materials research.

More information is available online.

Single-crystal yttrium iron garnet fabricated by metal-organic decomposition

The vast majority of electronic circuits and particular wireless communications, such as 5G cellular, and even quantum computing require high-quality low-loss oscillators. Current approaches relying on complementary metal oxide semiconductor technology are insuficient to meet future demand. A multi-institutional collaboration, led by Vida Products, a leader in high-frequency electronics, demonstrates the economic synthesis of single-crystal yttrium iron garnet films with low spin damping and large quality factors that has the potential to transform resonators and oscillators in future microelectronics.

This work was carried out in close collaboration with Allen Sweet (Vida Products), Yuri Suzuki (Stanford), Mingzhong Wu (Colorado State), and Peter Fischer and Stefano Cabrini (Berkeley Lab).

The original work was published in Appl. Phys. Lett. 119, 172405 (2021). 🔗

Physics and Art at the Nebraska fall summit

Promoting the integration of arts with sciences, Robert Streubel held a workshop about Physics and Art at the Nebraska Physics and Astronomy Fall Summit. This annual conference is hosted by the department of physics and astronomy at UNL drawing dozens of science teachers from throughout the state.

Check it out. 🔗

Molecular beam epitaxy system operational

After a long-awaited delivery and commissioning, our ultra-high vacuum deposition chamber is looking great on-site and is operational for our ambitious research projects. It is the latest and greatest addition to our laboratory that will allow us to synthesize transition metal-metalloid films with tailored spin-orbit coupling and topological phenomena.

We are thrilled to see where it will lead us.

Many thanks to Karl Eberl, Christian Caspers, Frank Huber, and Henning Fricker (MBE Komponenten), and Claudio Goncalves, and John Braun (United Mineral & Chemical) who have been working on this project for more than a year.

Artwork featured on poster for the conference for undergradaute women in physical sciences

The annual conference for undergradaute women in physical sciences is back - in person and at UNL - from October 21 thru 23, 2021. And this year, our digital research data is featured on the official poster.

Check out more information at 🔗 to see why the National Aeronautics and Space Administration (NASA) and the National Science Foundation (NSF) stay involved.

Topological phase objects behave like high-temperature superconductors

What determines the stability and order of closely packed quasiparticles in magnetic materials? Do they breathe? In order to answer these questions, we leverage ultrashort pairs of x-ray pulses and investigate the stochastic, spontaneous fluctuations of long-range-ordered topological phases. The spin fluctuations slow down near the magnetic-field-induced critical point due to the inability for the system to energetically favor freezing. Check out our paper to learn why topological phase objects may have more in common with high-temperature superconductors than you think.

This work was led by Joshua Turner (SLAC) and carried out in close collaboration with Eric Fullerton and Sunil Sinha (UCSD), and Steve Kevan and Peter Fischer (Berkeley Lab).

The original work was published in Phys. Rev. Res. 3, 033249 (2021). 🔗

Our activities are highlighted in: SLAC | Newswise | Phys.org

Ruthi Zielinski receives Undergraduate Creativity And Research Experience Award

Congratulations Ruthi! Following a successful First Year Research Experience, Ruthi was awarded one of UNL's Undergraduate Creativity And Research Experience Awards. She will lead the numerical studies of ferromagnetic resonances in yttrium iron garnet nanofilms and actively contribute to the success of our Layman seed grant.

The art of nanoscience

Jocelyn Bosley (UNL Research Impact Coordinator), Courtney Matulka (NE 8th-grade science teacher), Shireen Adenwalla (UNL Physics faculty) and Robert Streubel release YouTube outreach video about the art of nanoscience.

Visualizing science and physical mechanisms and interactions may provide a route toward 1) increasing diversity and inclusion in science, technology, engineering, and mathematics, 2) engaging the general public, and 3) integrating arts with sciences in middle school, high school, college, grad school and even for professionals.

Check it out. 🔗

Layman seed grant

Robert Streubel receives a seed grant from the Jane Robertson Layman Fund held at the University of Nebraska Foundation to work on Ferromagnetic resonators for 5G cellular communications. This research will be carried out in close collaboration with Vida Products. The goal is to identify design strategies for high-band, tunable, energy-efficient resonators based on epitaxial yttrium iron garnet (YIG) nanofilms.

Perspective on magnetism in curved geometries

Most materials are imperfect and possess a local curvature that impacts physical properties across multiple length scales. In quantum materials, where correlations, entanglement, and topology dominate, curvature opens the path to novel characteristics and phenomena that have recently emerged and could have a dramatic impact on future fundamental and applied studies of materials. Particularly, magnetic systems hosting non-collinear and topological states and 3D magnetic nanostructures strongly benefit from treating curvature as a new design parameter to explore prospective applications in the magnetic field and stress sensing, microrobotics, and information processing and storage.

The perspective was published in J. Appl. Phys. 129, 210902 (2021). 🔗

Ilysa Blake joins as high school intern

We are excited to welcome Ilysa to our group! Ilysa is among select Lincoln high school students who will have the opportunity to experience academic research before joining UNL in autumn.

More information about the Nebraska Center for Materials and Nanoscience STEM Summer High School Internship can be found here.

Robert Streubel participates in the BES Roundtable on Cryogenic Electron Microscopy

Roundtable discussions and workshops hosted by the Department of Energy, Basic Energy Sciences (BES) conclude the status of energy-relevant research areas and identify research directions for a decades-to-century energy strategy.

Robert Streubel joined the Low-temperature Phenomena in Quantum Matter panel for the Roundtable on Research Opportunities in the Physical Sciences enabled by Cryogenic Electron Microscopy. Transmission electron microscopy is uniquely positioned to probe quantized spin excitations and topological phases in crystalline, amorphous/heterogeneous and heterostructured quantum materials by directly visualizing the magnetization vector field with phase contrast imaging and vector field tomography. Superior spatial resolution and sensitivity will enable to decipher the influence of structural, chemical and electronic heterogeneity on spin-orbit coupling and emergent topological objects.

More information about BES reports can be found here.

Bryce Herrington receives Undergraduate Creativity And Research Experience Award

Many congratulations to Bryce for receiving his UCARE award. Starting in June, Bryce will lead the assembly and control of a magneto-optical Kerr effect magnetometer, and leverage its sensitivity to characterize disordered materials.

More information about UNL's Undergraduate Creativity And Research Experience Award can be found here.

Bryce Herrington joins as undergraduate research assistant

We are excited to welcome Bryce to our group! Bryce will lead the assembly and control of a magneto-optical Kerr effect magnetometer, and leverage its sensitivity to characterize disordered materials. He will be involved in the Nebraska EPSCoR FIRST Award.

Ferromagnetic liquid droplets with adjustable magnetic properties

Structured functional liquids combine mechanical versatility of fluids with solid-state properties, such as ferromagnetism, and offer a route to synthesize and control magnetic liquids for adaptive liquid robotics. Studies on these intriguing materials are only in their nascent state, and a profound understanding of the physical state is still lacking. In this work, we use hydrodynamics experiments to probe how the magnetization of ferromagnetic liquid droplets, governed by the assembly and jamming of magnetic nanoparticles at liquid–liquid interfaces, and their response to external stimuli can be tuned by chemical, structural, and magnetic means. Our results highlight the leading role of structural short-range order on magnetic properties, which provide a path toward nano-patterning structured liquids.

The work was carried out in collaboration with the Berkeley Lab's Materials Sciences Division.

The original work was published in Proc. Natl. Acad. Sci. USA 118, e2017355118 (2021). 🔗

Our activities are highlighted in: CommUnique News from the Department of Energy, Office of Science | Nebraska Today | Tohoku University

Nebraska EPSCoR FIRST Award

Robert Streubel receives the Nebraska EPSCoR FIRST Award following positive evaluation by experts from the U.S. magnetism community. This seed grant is awarded to five recipients from the University of Nebraska system to prepare a competitive NSF CAREER grant application.

The Nebraska EPSCoR FIRST Award is funded by the National Science Foundation's (NSF) infrastructure grant to Nebraska EPSCoR and provides assistance to Nebraska's early-career, tenure-track faculty.

More information can be found online. 🔗

Topological magnetism emerges in amorphous materials

Single-crystals and multilayer heterostructures with global inversion symmetry breaking can promote the formation of topological solitary vector fields owing to a vector spin exchange known as the Dzyaloshinskii-Moriya interaction (DMI). - And so can short-range order. - In this work, we report experimental evidence of 3D chiral spin textures, i.e., helical spins and skyrmions with different chirality and topological charge, stabilized in amorphous Fe–Ge thick films. Our results demonstrate that structurally and chemically disordered materials with a random DMI can resemble inversion symmetry broken systems with similar magnetic properties, moments, and states. Yet, disordered systems are distinct by their degenerate spin chirality that allows for forming isotropic and anisotropic topological spin textures at remanence while offering greater flexibility in materials synthesis, voltage and strain manipulation, and an enhanced spin-orbit coupling relevant to prospective microelectronics applications.

The work was carried out in collaboration with the University of California, Berkeley, and at Berkeley Lab's Advanced Light Source, National Center for Electron Microscopy, and Materials Sciences Division.

The original work was published in Adv. Mater. 33, 2004830 (2021). 🔗

It is featured as a cover art. 🔗

Suvechhya Lamichhane and Bibek Tiwari join as graduate research assistants

We are excited to welcome Suvechhya and Bibek to the group! Suvechhya and Bibek are second-year graduate students in the Physics department. Their work will focus on numerical modeling of temperature, strain and resonance effects in exchange and dipole-couple materials in preparation of experimental studies.

Ruthi Zielinski joins as undergraduate research assistant

Welcome to the group, Ruthi! We are excited to have you on-board. Ruthi received one of UNL's First Year Research Experience (FYRE) awards. Her research concerns numerical studies of order-by-short-range order phenomena in dipole-coupled macro spin systems.

2020 Emerging Leaders of the Journal of Physics: Condensed Matter

Robert Streubel is recognized as an Emerging Leader by the Journal of Physics: Condensed Matter. His special issue contribution "The effect of Cu additions in FePt-BN-SiO₂ heat-assisted magnetic recording media" focuses on the impact of structural and chemical order in L1₀ FePt. Two copper-driven mechanisms, although competing, can lead to improvements in both structural and magnetic properties. Cu substitution on the Fe-site degrades magnetic properties due to delocalized electron orbitals originating from a larger Cu d-orbital occupancy. At the same time, Cu enhances crystallographic order and consequently magneto-crystalline anisotropy, which offsets the former effect to a great extent.

The work was carried out in collaboration with Western Digital and at Berkeley Lab's Advanced Light Source.

The work was published in J. Phys.: Condens. Matter 33, 104003 (2021) 🔗 as part of the 2020 Emerging Leaders special issue.

Perspective on ferromagnetic liquids

Assembly and jamming of nanoparticles at liquid interfaces is a versatile approach to construct liquids with solid-state properties. These hierarchical systems obtain their functionality from the short-range order and properties of individual nanoparticles. Using superparamagnetic nanoparticles imparts a magnetic moment, contrary to ferrofluids, and enables heterostructuring of the interface, when using various types of nanoparticles. We discuss recent advances in synthesis and characterization, and outline future scientific and technological directions, challenges and application potential of all-liquid robotics.

The perspective was published in Materials 13, 2712 (2020). 🔗

Launching a new dimension with 3D magnetic nanostructures

Three-dimensional magnetic nanostructures emerge from bulk and 2D planar materials with exciting novel physical phenomena originating from the increased complexity in spin textures, topology, and frustration in three dimensions. They bear tremendous potential for applications in magnetic sensing and information processing technologies in terms of improved energy efficiency, processing speed, functionalities, and miniaturization of future spintronic devices. We provide an overview of recent progress and scientific challenges with regard to advances in synthesis approaches and state-of-the-art nanoscale characterization techniques that are prerequisite to understand, realize, and control the properties, behavior, and functionalities of three-dimensional magnetic nanostructures.

The review was published in APL Materials 8, 010701 (2020). 🔗

Reconfigurable ferromagnetic liquid droplets

Have you ever wondered whether a liquid could be ferromagnetic? - Ferrofluids, although reconfigurable, lose their magnetic moment and thus functionality upon removal of the external magnetic field. - In our work, we manufacture a material that is mechanically a liquid and possesses magnetic properties of a solid magnet. It can be easily reconfigured into different shapes while preserving the magnetic properties of solid ferromagnets with classic north-south dipole interactions. These novel functionalities rely on a reversible paramagnetic-to-ferromagnetic transformation of ferrofluid droplets by the jamming of a monolayer of magnetic nanoparticles assembled at the water-oil interface.

"This new liquid is [...] mesmerizing [...] and could be a boon to medicine and robotics" (New York Times).

The work was carried out in collaboration with Berkeley Lab's Materials Sciences Division.

The original work was published in Science 365, 264 (2019). 🔗

Our activities are highlighted in: Science Perspective | Science Podcast | New York Times | Berkeley Lab | Newswise | Science News | Phys.org | pro-physik.de

Special issue on 3D nano magnetism and magnetic materials

Advances in synthesis science and characterization techniques combined with novel concepts for microelectronics, magnetic storage, and sensing applications have fueled the appeal of 3D nano magnetism. This vital research area is comprised of magnetic nano structures, nano membranes, and particle assemby, as well as 3D magnetization vector fields driven by vector spin exchange or spin frustration in heterogeneous condensed matter. In these systems, new functionalities emerge owing to the nano scale features of magnetization. The emergence of topological magnetic states, on the nano scale, renders magnetic materials in the light of quantum materials, which are envisioned to serve future microelectronics based on neuromorphic computing and racetrack memory applications.

This Special Issue welcomes original research contributions and review articles highlighting recent advances and future directions in the field of 3D nano magnetism and magnetic materials. 🔗

Review on x-ray ptychography

Tailoring structural, chemical, and electronic (dis-)order in heterogeneous media is one of the transformative opportunities to enable new functionalities and sciences in energy and quantum materials. This endeavor requires elemental, chemical, and magnetic sensitivities at the nano/atomic scale in 2D and 3D space. One of the most promising methods is coherent diffraction imaging, namely, x-ray ptychography, which is envisioned to take on the dominance of electron imaging techniques offering atomic resolution in the age of diffraction limited light sources. In this review, we discuss the current research examples of far-field diffraction-based x-ray ptychography on 2D and 3D semiconductors, ferroelectrics, and ferromagnets and their blooming future as a mainstream tool for materials sciences.

The review was published in Appl. Phys. Rev. 6, 011306 (2019). 🔗

Observation of order-by-short-range order phenomena in XY macro spin lattices

The appeal of geometric frustration is fueled by exotic physical behaviors originating from a macroscopic ground state degeneracy, which manifest spin ices, spin glasses, quantum spin liquids, vortices, Skyrmions, and Hopfions. In our work, we investigate magnetic phases and correlations of planar XY macro spin lattices and report the experimental observation of magnetic ground states through direct imaging, predicted three decades ago. The possibility to fabricate and investigate XY dipolar systems at the micro scale opens up a new avenue in the field of artificial spin ice toward XY spins, spin liquids, Kitaev’s XYZ honeycomb lattices, and magnonics with tunable interactions.

The work was carried out in collaboration with Berkeley Lab's Advanced Light Source, Molecular Foundry, and Materials Sciences Division.

The original work was published in Nano Lett. 18, 7428 (2018). 🔗

It is featured as a cover art. 🔗

Experimental evidence of chiral ferrimagnetism

To date, chiral spin textures, such as Skyrmions, have mainly been studied in helimagnets and thin ferromagnets with heavy-element capping. In our work, we present experimental evidence that the concept of chirality driven by interfacial Dzyaloshinskii–Moriya interaction can be generalized to complex multicomponent systems, and demonstrate it on the example of chiral ferrimagnetism in amorphous GdCo films, utilizing high-resolution Lorentz microscopy with exit wave reconstruction and quantitative x-ray magnetic circular dichroism spectroscopy. Our findings open up a new avenue towards investigating chirality effects in spin orbitronics, spin caloritronics, all-optical switching and phase transitions.

The work was carried out in collaboration with the University of California, Berkeley, and at Berkeley Lab's Advanced Light Source, National Center for Electron Microscopy, and Materials Sciences Division.

The original work was published in Adv. Mater. 30, 1800199 (2018). 🔗

It is featured as a front-is-piece cover art. 🔗

Our activities are highlighted in: Newswise | Berkeley Lab | Phys.org | EurekAlert

Robert Streubel invited to participate in 2017 CREDITS retreat

The Center for Research, Excellence and Diversity in Team Science (CREDITS) is an integrated research and training program to increase and enhance Team Science (TS) and collective intelligence capacity, effectiveness, and excellence in California. Diversity on teams is known to have positive effects on creativity, innovation, and productivity. Apart from its contribution to scientific breakthroughs and grand challenge problems, TS has beneficial impacts on individual research careers. Diverse TS projects garner more funding, and yield greater publication productivity, and higher impact publications.

Robert Streubel had the great honor to be one of 22 faculty-track attendees selected from the CSU and UC systems. The retreat has been an invaluable experience for extending perception of good leadership and networking with dedicated team players ranging from recently appointed tenure-track to senior professors.

More information on this intriguing program and retreat can be found online. 🔗

Nanosecond x-ray photon correlation spectroscopy

Coherent x-ray scattering has emerged as one of the leading tools to study microscopic fluctuations in materials. However, the temporal resolution for the so-called x-ray photon correlation spectroscopy (XPCS) is limited by coherence and acquisition, and at best a few microseconds. Using a pair of x-ray pulses generated by two individual excitation lasers at the free electron laser LCLS (SLAC National Accelerator Laboratory), we were able to probe fluctuations in magnetic Skyrmion phases on nanosecond time scales. This work was led by Joshua Turner (SLAC) and Sujoy Roy (Berkeley Lab), and carried out in close collaboration with Eric Fullerton and Sunil Sinha (UCSD), and Steve Kevan and Peter Fischer (Berkeley Lab).

The original work was published in Phys. Rev. Lett. 119, 067403 (2017). 🔗

Our activities are highlighted in: Physics | MRS Bulletin | Newswise | SLAC | Berkeley Lab | Phys.org | Nanowerk | Advantage Business Media | Long Room

Review on three-dimensional nanomagnetism

Whereas patterned nanomagnets are traditionally two-dimensional planar structures, recent work is expanding nanomagnetism into three dimensions; a move triggered by the advance of unconventional synthesis methods and the discovery of new magnetic effects. In three-dimensional nanomagnets more complex magnetic configurations become possible, many with unprecedented properties. We address the creation of these structures and their implications for the emergence of new physics, the development of instrumentation and computational methods, and exploitation in numerous applications.

The review was published in Nat. Commun. 8, 15756 (2017). 🔗

Topical review selected for inclusion in "Highlights of 2016"

Our topical review on Magnetism in curved geometries has been selected by the Editorial Board of the Journal of Physics D: Applied Physics for inclusion in the 50th anniversary's "Highlights of 2016" collection. 🔗

The citation reads:

"Magnetism in curved geometries" by Robert Streubel, Peter Fischer, Florian Kronast, Volodymyr P Kravchuk, Denis D Sheka, Yuri Gaididei, Oliver G Schmidt and Denys Makarov has been selected by the Editorial Board of Journal of Physics D: Applied Physics for inclusion in the exclusive "Highlights of 2016" collection, and were chosen on the basis of timeliness, scientific impact and broadness of appeal.

Master student Sven Velten graduates with distinction

Congratulations to Sven Velten who graduated in Physics with distinction from the University Hamburg, Germany. He had been with our group for one year working on "Magnetic Interactions in Nanodisk Arrays", and my very first directly supervised master student. We wish him all the best for his future scientific career.

ALS UEC gets a new website

Reforming nominations and elections processes to enhance engagement, efficiency and diversity of UEC members is only one aspect of current UEC's business. In order to improve the visibility and public engagement with ALS users, ALS staff and external parties, and incorporate those changes, I redesigned the UEC website from scratch hosting all UEC related activities.

The online presence was officially launched right before the ALS Users' Meeting. 🔗

Topical review on curved magnetic geometries

Bending and twisting two-dimensional structures into three-dimensional space can modify conventional or help to discover novel functionalities in electronic, photonic, plasmonic or magnetic devices. In the first review on “Magnetism in curved geometries”, we discuss the emerging peculiarities in geometrically curved magnetic thin films. A profound introduction to fundamental physics, state-of-the-art characterization and fabrication techniques as well as to perspectives and applications is given highlighting the great potential of this new research area.

The review was published in J. Phys. D: Appl. Phys. 49, 363001 (2016). 🔗

The review is highlighted in: JPhys+

It has been selected by the Editorial Board of the Journal of Physics D: Applied Physics for inclusion in the "Highlights of 2016" collection. 🔗

Founding board member of the Berkeley Lab Postdoc Association

Robert Streubel joins the Berkeley Lab Postdoc Association as founding board member. It acts to enrich the postdocs' scientific careers through various social and professional events and activities. One of our foci is set on networking among postdocs and with students, alumni and senior scientists.

More information can be found here: homepage | LinkedIn | facebook | Twitter

Robert Streubel named program co-chair of the ALS users' meeting 2016

Taking action as newly elected members of the ALS UEC, Fanny Rodolakis and Robert Streubel will co-chair the scientific programme of the ALS users' meeting 2016. The ALS users' meeting takes place October 3-5, 2016 and provides a platform for scientific exchange and networking across disciplines. Experienced researchers and students are invited to advance expertise attending plenary addresses and focused workshop sessions on state-of-the-art techniques and research. 🔗

Robert's dissertation honored with Ernst-Eckhard-Koch-Prize 2015

The Society of Friends of Helmholtz-Zentrum Berlin (HZB) announces each year the Ernst-Eckhard-Koch-Prize, which is bestowed for outstanding doctoral theses in the field of research with synchrotron radiation performed at German synchrotron radiation facilities. The Ernst-Eckhard-Koch-Prize includes a monetary award of 2500 €.

Robert Streubel's dissertation has been selected by the committee. He was awarded the prize in a ceremony during the Users' Meeting of the HZB on December 10, 2015. 🔗

Robert Streubel elected member of ALS UEC

The Users' Executive Committee (UEC) at the Advanced Light Source (ALS) represents the users' interest at the ALS. Among an outstanding slate of 11 scientists, three new regular members including myself were elected to join UEC for three years. Thank you everyone for your support.

In his function, Robert will help the ALS promoting the unique potential of synchrotron radiation specifically to younger students thinking about entering one of the many fields, where synchrotron radiation can have a dramatic impact, but also to the many visitors coming to the ALS on a daily base. He is also interested in helping our UEC communicating to our political representatives the importance of continued and sufficient funding of large scale facilities by working with the NUFO organization.

More information can be found here. 🔗

Dissertation by Robert Streubel

Dissertation entitled Imaging Spin Textures on Curved Magnetic Surfaces is evaluated with summa cum laude by the faculty of natural sciences of the TU Chemnitz.

The thesis summarizes pioneering research activities on visualizing spin textures on 3D curved magnetic surfaces that have been highlighted as numerous publications in high-ranked journals, including Nature Communications, Nano Letters and Advanced Materials. It represents a first milestone in 3D imaging of magnetic microtextures by reconstruction utilizing Magnetic soft x-ray Tomography (MXT), a visualization technique relying on x-ray magnetic circular dichroism (XMCD) as element-specific contrast mechanism. Two distinct 3D curved magnetic surfaces, namely magnetic cap structures and rolled-up magnetic nanomembranes with cylindrical shape are experimentally investigated in view of fundamental physics, e.g. curvature- and topology-driven modifications to magnetic domain configurations, magnetization reversal processes and spin excitations, and applications as storage devices, sensors and self-propelled targeted drug delivery.

The work is honored with:

• Ernst-Eckhard-Koch-Prize 2015 by the Society of Friends of Helmholtz-Zentrum Berlin (HZB)
• Leibniz Dissertation Award Finalist 2016 of the Leibniz Association, Germany
• Ehrenfried Walther von Tschirnhaus-Plakette 2016 by the IFW Dresden
• Condensed Matter Dissertation Prize Finalist 2016 of the German Physical Society

The dissertation is available at Qucosa. 🔗

Magnetic soft x-ray tomography

While x-ray tomography is extensively applied, its magnetic analog – magnetic x-ray tomography – although demanded for medical applications and materials sciences, had not been available. We put forth the foundation of magnetic soft x-ray tomography and demonstrate its capabilities by reconstructing 3D spin textures of microscopic tubular architectures. This work was carried out in close collaboration with partners at the Helmholtz-Zentrum Berlin, BESSY II (Dr. Florian Kronast) and Advanced Light Source at Berkeley (Dr. Peter Fischer).

The original work was published in Nat. Commun. 6, 7612 (2015). 🔗

Our activities are highlighted in: pro-physik.de | Nanowerk | Nanotechnology Now | Analytica-world | Jura-Forum | HZB, BESSY II