Dr. Sebastian Gliga
5232 Villigen PSI
Sebastian Gliga is a Scientist in the Microspectroscopy Group and at the PolLux Scanning Transmission X-ray Microscopy (STXM) beamline. He has a BSc and an MSc in Physics from McGill University (Canada). His MSc research was in experimental particle physics, performed at DESY (Germany). He did his PhD in Condensed Matter Physics at the Forschungszentrum Jülich (Germany), graduating from the Universität Duisburg-Essen. Sebastian Gliga was a Center for Nanoscale Materials Distinguished Fellow at Argonne National Laboratory (USA), a Fellow at the Max Planck Institute for Microstructure Physics (Germany) and a Marie Curie Fellow at the University of Glasgow (UK). He has also occupied Postdoctoral and Scientist positions at the ETH Zürich.
Sebastian Gliga’s scientific research focuses on nanomagnetism, in particular the investigation of emergent phenomena in two- (2D) and three-dimensional (3D) artificial spin systems with the goal of creating functional materials. Projects include the nanofabrication of 2D and 3D artificial spin systems on the micron scale as well as their characterization using synchrotron-based tools. A recent project investigates the possibility of using graphene to achieve reconfigurable magnetic nanosystems.
Sebastian Gliga has published 60 peer-reviewed papers that have been cited more than 2300 times.
Spin-Wave Dynamics and Symmetry Breaking in an Artificial Spin Ice, Susmita Saha, Jingyuan Zhou, Kevin Hofhuis, Attila Kákay, Valerio Scagnoli, Laura J. Heyderman, Sebastian Gliga, Nano Letters 21, 2382–2389 (2021)
Artificial spin ices are periodic arrangements of interacting nanomagnets which allow investigating emergent phenomena in the presence of geometric frustration. Recently, it has been shown that artificial spin ices can be used as building blocks for creating functional materials, such as magnonic crystals. We investigate the magnetization dynamics in a system exhibiting anisotropic magnetostatic interactions owing to locally broken structural inversion symmetry. We find a rich spin-wave spectrum and investigate its evolution in an external magnetic field. We determine the evolution of individual modes, from building blocks up to larger arrays, highlighting the role of symmetry breaking in defining the mode profiles. Moreover, we demonstrate that the mode spectra exhibit signatures of long-range interactions in the system. These results contribute to the understanding of magnetization dynamics in spin ices beyond the kagome and square ice geometries and are relevant for the realization of reconfigurable magnonic crystals based on spin ices.
Experimental observation of vortex rings in a bulk magnet, Claire Donnelly, Konstantin L. Metlov, Valerio Scagnoli, Manuel Guizar-Sicairos, Mirko Holler, Nicholas S. Bingham, Jörg Raabe, Laura J. Heyderman, Nigel R. Cooper, Sebastian Gliga, Nature Physics 17, 316–321 (2021)
Vortex rings are remarkably stable structures that occur in a large variety of systems, such as in turbulent gases, fluids, electromagnetic discharges and plasmas. Although vortex rings have also been predicted to exist in ferromagnets, they have not yet been observed. Using X-ray magnetic nanotomography, we imaged three-dimensional structures forming closed vortex loops in a bulk micromagnet. The cross-section of these loops consists of a vortex–antivortex pair and, on the basis of magnetic vorticity, we identify these configurations as magnetic vortex rings. Although such structures have been predicted to exist as transient states in exchange ferromagnets, the vortex rings we observe exist as static configurations, and we attribute their stability to the dipolar interaction. In addition, we find stable vortex loops intersected by point singularities at which the magnetization within the vortex and antivortex cores reverses. These observations open up possibilities for further studies of complex three-dimensional solitons in bulk magnets, enabling the development of applications based on three-dimensional magnetic structures.
Time-resolved imaging of three-dimensional nanoscale magnetization dynamics, Claire Donnelly, Simone Finizio, Sebastian Gliga, Mirko Holler, Aleš Hrabec, Michal Odstrčil, Sina Mayr, Valerio Scagnoli, Laura J. Heyderman, Manuel Guizar-Sicairos, Jörg Raabe, Nature Nanotechnology 15, 356–360(2020)
Understanding and control of the dynamic response of magnetic materials with a three-dimensional magnetization distribution is important both fundamentally and for technological applications. Here, we demonstrate time-resolved magnetic laminography, a pump–probe technique, which offers access to the temporal evolution of a three-dimensional magnetic microdisc with nanoscale resolution, and with a synchrotron-limited temporal resolution of 70 ps. We image the dynamic response to a 500 MHz magnetic field of the complex three-dimensional magnetization in a two-phase bulk magnet with a lateral spatial resolution of 50 nm. Our technique, which probes three-dimensional magnetic structures with temporal resolution, enables the experimental investigation of functionalities arising from dynamic phenomena in bulk and three-dimensional patterned nanomagnets.
Dynamics of reconfigurable artificial spin ice: Toward magnonic functional materials, Sebastian Gliga, Ezio Iacocca, Olle Heinonen, APL Materials 8, 040911 (2020)
Over the past few years, the study of magnetization dynamics in artificial spin ices has become a vibrant field of research. Artificial spin ices are ensembles of geometrically arranged, interacting magnetic nanoislands, which display frustration by design. Recently, it has become clear that it is possible to create artificial spin ices, which can potentially be used as functional materials. In this perspective, we review the resonant behavior of spin ices in the GHz frequency range, focusing on their potential application as magnonic crystals. The applicability of spin ices to create magnonic crystals hinges upon their reconfigurability. Consequently, we describe recent work aiming to develop techniques and create geometries allowing full reconfigurability of the spin ice magnetic state. We also discuss experimental, theoretical, and numerical methods for determining the spectral response of artificial spin ices and give an outlook on new directions for reconfigurable spin ices.
Stray-Field Imaging of a Chiral Artificial Spin Ice during Magnetization Reversal, Marcus Wyss, Sebastian Gliga, Denis Vasyukov, Lorenzo Ceccarelli, Giulio Romagnoli, Jizhai Cui, Armin Kleibert, Robert L. Stamps, Martino Poggio, ACS Nano 13, 13910–13916 (2019)
Artificial spin ices are a class of metamaterials consisting of magnetostatically coupled nanomagnets. Their interactions give rise to emergent behavior, which has the potential to be harnessed for the creation of functional materials. Consequently, the ability to map the stray field of such systems can be decisive for gaining an understanding of their properties. Here, we use a scanning nanometer-scale superconducting quantum interference device (SQUID) to image the magnetic stray field distribution of an artificial spin ice system exhibiting structural chirality as a function of applied magnetic fields at 4.2 K. The images reveal that the magnetostatic interaction gives rise to a measurable bending of the magnetization at the edges of the nanomagnets. Micromagnetic simulations predict that, owing to the structural chirality of the system, this edge bending is asymmetric in the presence of an external field and gives rise to a preferred direction for the reversal of the magnetization. This effect is not captured by models assuming a uniform magnetization. Our technique thus provides a promising means for understanding the collective response of artificial spin ices and their interactions.
Architectural structures open new dimensions in magnetism: Magnetic buckyballs, Sebastian Gliga, Gediminas Seniutinas, Anja Weber, Christian David, Materials Today 26, 100-101 (2019)
Over 60 years ago, Buckminster Fuller, a visionary inventor and architect, introduced a revolutionary concept in structural engineering: the geodesic dome. Today, the advent of modern nanofabrication tools has opened exciting new possibilities for defining structures on scales ranging from hundreds of micrometers down to tens of nanometers. However, only recently could such small structures be realized in three dimensions – and Buckminster Fuller’s principles have again proven essential. Indeed, his ideas find direct applications in structures such as mechanical metamaterials, which combine macroscopic mechanical properties with bio-inspired architectures to create materials with unprecedented strength and properties. Now, we add an additional degree of freedom to such materials: magnetism. As a proof of concept for the fabrication of a three-dimensional artificial spin system, we have chosen a mesoscopic buckyball.The structure allows investigating emergent magnetic properties, while the connected network of bars can also define paths for domain wall propagation that could conceivably be used to perform logical operations.
Emergent dynamic chirality in a thermally driven artificial spin ratchet, Sebastian Gliga, Gino Hrkac, Claire Donnelly, Jonathan Büchi, Armin Kleibert, Jizhai Cui, Alan Farhan, Eugenie Kirk, Rajesh V. Chopdekar, Yusuke Masaki, Nicholas S. Bingham, Andreas Scholl, Robert L. Stamps, Laura J. Heyderman, Nature Materials 16, 1106–1111 (2017)
Modern nanofabrication techniques have opened the possibility to create novel functional materials, whose properties transcend those of their constituent elements. In particular, tuning the magnetostatic interactions in geometrically frustrated arrangements of nanoelements called artificial spin ice can lead to specific collective behaviour. Here, we demonstrate a spin-ice-based active material in which energy is converted into unidirectional dynamics. Using X-ray photoemission electron microscopy we show that the collective rotation of the average magnetization proceeds in a unique sense during thermal relaxation. Our simulations demonstrate that this emergent chiral behaviour is driven by the topology of the magnetostatic field at the edges of the nanomagnet array, resulting in an asymmetric energy landscape. This opens the possibility of implementing a magnetic Brownian ratchet, which may find applications in novel nanoscale devices, such as magnetic nanomotors, actuators, sensors or memory cells.
Three-dimensional magnetization structures revealed with X-ray vector nanotomography, Claire Donnelly, Manuel Guizar-Sicairos, Valerio Scagnoli, Sebastian Gliga, Mirko Holler, Jörg Raabe, Laura J. Heyderman, Nature 547, 328–331 (2017)
In soft ferromagnetic materials, the smoothly varying magnetization leads to the formation of fundamental patterns such as domains, vortices and domain walls. These have been studied extensively in thin films of thicknesses up to around 200 nanometres, in which the magnetization is accessible with current transmission imaging methods that make use of electrons or soft X-rays. In thicker samples, however, in which the magnetization structure varies throughout the thickness and is intrinsically three dimensional, determining the complex magnetic structure directly still represents a challenge. We have developed hard-X-ray vector nanotomography with which to determine the three-dimensional magnetic configuration at the nanoscale within micrometre-sized samples. We imaged the structure of the magnetization within a soft magnetic pillar of diameter 5 micrometres with a spatial resolution of 100 nanometres. We observed complex magnetic configurations, including the three-dimensional magnetic structure in the vicinity of magnetic singularities —Bloch points—, which have been predicted over fifty years ago. Our imaging method allows accessing magnetic textures, which are critical for understanding macroscopic magnetic properties and for designing micromagnets for technological applications.
Nanoscale control of competing interactions and geometrical frustration in a dipolar trident lattice, Alan Farhan, Charlotte F. Petersen, Scott Dhuey, Luca Anghinolfi, Qi Hang Qin, Michael Saccone, Sven Velten, Clemens Wuth, Sebastian Gliga, Paula Mellado, Mikko J. Alava, Andreas Scholl, Sebastiaan van Dijken, Nature Communications 8, 995 (2017)
Geometrical frustration occurs when entities in a system, subject to given lattice constraints, are hindered from simultaneously minimizing their local interactions. In magnetism, systems incorporating geometrical frustration are fascinating, as their behavior is not only hard to predict, but also leads to the emergence of exotic states of matter. Here, we provide a first look into an artificial frustrated system in which the balance of competing interactions between nearest-neighbor magnetic moments can be directly controlled, thus allowing versatile tuning of geometrical frustration and manipulation of ground state configurations. Our findings not only provide the basis for future studies on the low-temperature physics of this lattice, but also demonstrate how the concept of frustration-by-design can deliver magnetically frustrated metamaterials.
Nanoscale switch for vortex polarization mediated by Bloch core formation in magnetic hybrid systems, Phillip Wohlhüter, Matthew Thomas Bryan, Peter Warnicke, Sebastian Gliga, Stephanie Elizabeth Stevenson, Georg Heldt, Lalita Saharan, Anna Kinga Suszka, Christoforos Moutafis, Rajesh Vilas Chopdekar, Jörg Raabe, Thomas Thomson, Gino Hrkac & Laura Jane Heyderman, Nature Communications 6, 7836 (2015)
Vortices are fundamental magnetic topological structures characterized by a curling magnetization around a highly stable nanometric core. The control of the polarization of this core and its gyration is key to the utilization of vortices in technological applications. So far polarization control has been achieved in single-material structures using magnetic fields, spin-polarized currents or spin waves. Here we demonstrate local control of the vortex core orientation in hybrid structures where the vortex in an in-plane Permalloy film coexists with out-of-plane maze domains in a Co/Pd multilayer. The vortex core reverses its polarization on crossing a maze domain boundary. This reversal is mediated by a pair of magnetic singularities, known as Bloch points, and leads to the transient formation of a three-dimensional magnetization structure: a Bloch core. The interaction between vortex and domain wall thus acts as a nanoscale switch for the vortex core polarization.