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09/2018

Observation of order-by-disorder 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 original work was published in Nano Lett. (2018). 🔗

05/2018

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 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 | LBNL | Phys.org | EurekAlert

10/2017

Invited participant at 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.

I 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. 🔗

08/2017

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 (LBNL), and carried out in close collaboration with Eric Fullerton and Sunil Sinha (UCSD), and Steve Kevan and Peter Fischer (LBNL).

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

06/2017

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). 🔗

04/2017

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.

12/2016

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. I wish him all the best for his future scientific career.

10/2016

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. 🔗

08/2016

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. 🔗

04/2016

Founding board member of the Berkeley Lab Postdoc Association

The recently founded Berkeley Lab Postdoc Association 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

01/2016

Program co-chair of the ALS users' meeting 2016

Taking action as newly elected members of the ALS UEC, Fanny Rodolakis and myself 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. 🔗

12/2015

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 €.

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

11/2015

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 my function, I 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. I am 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. 🔗

08/2015

Dissertation

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. 🔗

07/2015

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). 🔗