Research statement

My research focuses on spintronics, a subfield of materials physics which exploits the spin of electrons as an additional degree of freedom besides their electric charge that is already used in electronics applications.

I am mostly interested in magnetic films, multilayers, alloys and nanostructures. My research is both experimental and computational. The overarching goal is to explore novel physical phenomena with a potential for applications in unconventional computing approaches. Such phenomena include but are not limited to magnetic skyrmions, spin waves (magnons), and spin torques.

Not only in my research projects, but also in the classroom I have developed a strong passion for computational methods. I believe that students should acquire computational literacy as early as possible. Therefore, I have become an advocate of embedding computational contents into undergraduate curricula. 

Ongoing research projects

Computational methods in science and engineering teaching; 2020-present

At the Department of Materials Science and Engineering at the University of Illinois at Urbana-Champaign, we have carried out a systematic case study on how numerical simulations can be embedded into traditional coursework and we investigated how students may benefit from computational content in lectures, laboratories and assignments. We defined computational projects and assigned them to small groups of two to four students. Students were asked to use the Ubermag software package in order to drive micromagnetic simulations by writing and running Python code in Jupyter notebooks.   

Static and dynamic properties of magnetic nanostructures; 2022-2023

We use micro-Hall magnetometry and micromagnetic simulations to understand the magnetization reversal of three-dimensional nanostructures fabricated by focused electron beam induced deposition (FEBID) in the group of Prof. Dr. Michael Huth. We also compare our results with macro-spin simulations by our collaborator from the University of Bielefeld and FH Bielefeld, Prof. Dr. Christian Schröder. Furthermore, we plan to study first-order reversal curves of 2D and 3D nanoarchitectures by means of GPU-accelerated micromagnetic modeling and experiments. 

Past research projects

Skyrmion dynamics in magnetic multilayers; 2019-2022

Skyrmions are topologically protected chiral magnetic textures that occur in a variety of material systems such as thin films or magnetic multilayers, even at room temperature. A promising characteristic of these magnetic whirls is that relatively small electric current densities are sufficient to induce their motion which could, for example, be exploited in future memory devices. In addition, the resonant eigenexcitations of skyrmions and other related objects -- typically in the GHz frequency range -- are also highly relevant for both fundamental research and technological applications. Present issues include the theoretical understanding as well as the experimental observation of such resonances in thin films or magnetic multilayers, which often exhibit high Gilbert damping parameters, structural inhomogeneities, disorder and defects. 

Electronic transport studies on transition metal oxide-based Resistive Random Access Memory (RRAM) devices; 2017-2020

Resistive random access memory (RRAM) devices have attracted great attention due to their potential to be applied as a reliable, fast and high-density non-volatile data storage solution. In transition metal oxide-based devices, the mechanism of resistive switching is related to the formation and rupture of oxygen-deficient conducting filaments in the oxide layer. Up until today, the exact mechanisms of charge transport and their dependence on various parameters are not yet fully understood. Fluctuation (noise) spectroscopy measurements can help to provide a better understanding of the transport behavior. For example, in the case of Y2O3-based RRAMs the noise magnitude in the high resistive state systematically decreases through dc training. This effect is attributed to the stabilization of the conductive filament via the consumption of oxygen vacancies, thus reducing the number of active fluctuators in the vicinity of the filament. 

Resistance noise spectroscopy of the magnetic semiconductors (Ga,Mn)As and (Ga,Mn)P; 2013-2018

Diluted magnetic semiconductors combine the benefits of magnetic and semiconducting materials and are thus considered promising candidates for future spintronics applications. Despite extensive studies on the prototypic compounds (Ga,Mn)As and (Ga,Mn)P, the precise electronic structure and the exact mechanism of the carrier-mediated long-range ferromagnetic order are still under debate. Theoretical approaches range from the assumption of free charge carriers (p-d Zener model) to the opposite case of strongly localized carriers (impurity-band model). In the latter case, an intriguing concept for the origin of spontaneous magnetization is the percolation of bound magnetic polarons. Fluctuation spectroscopy has been shown to be sensitive to the presence of such magnetic (and/or electronic) inhomogeneities. Indeed, for the case of insulating (Ga,Mn)As and (Ga,Mn)P films a strong increase of the resistance noise magnitude around the Curie temperature indicates the presence and percolation of magnetic polarons. 

Micro-Hall magnetometry studies of ferromagnetic micro-particles; 2012-2013

Micro-Hall-magnetometry is a powerful technique for studying the magnetization dynamics of micrometer- and nanometer-scale particles. The utilized sensors are based on the two-dimensional electron gas in GaAs/AlGaAs heterostructures and allow for magnetic stray-field measurements of individual micron-sized particles of Lu2MnCoO6 positioned on one or several lithographically defined Hall crosses. 

Methods and Techniques

A list of relevant methods employed during my past and present research projects can be found in the following: 

Fluctuation (noise) spectroscopy, electronic transport measurements (including resistance, Hall and anomalous Hall effect studies), SQUID VSM magnetometry, magnetron sputtering deposition, thin film deposition by thermal and electron-beam evaporation, X-ray reflectometry, optical lithography, wet chemical etching, magneto-optical Kerr microscopy, micro-Hall magnetometry, micromagnetic simulations (OOMMF, mumax3 and Ubermag), programming of measuring instruments and data-processing scripts with Python, dielectric spectroscopy and dielectric polarization noise measurements, ultrasonic bonding, atomic force microscopy, He-4 bath cryostats (including He-3 option), continuous flow cryostats, closed cycle refrigerators, preparation of lamella samples for transmission electron microscopy investigations with focused-ion beam etching, transmission electron microscopy.