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Stephan Geprägs

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Technische Physik

Lehrveranstaltungen und Termine

Ausgeschriebene Angebote für Abschlussarbeiten

Elektrisch gesteuerter Magnontransport in magnetisch geordneten Isolatoren

Angular momentum transport in magnetically ordered insulators is carried by magnetic excitation quanta in contrast to magnetic conductors, where mobile charge carrier also carry angular momentum. In magnetically ordered insulator/normal metal hybrids it is possible to study the transport of angular momentum by all-electrical means via the spin Hall and inverse spin Hall effect in the normal metal. The focus of this project is the investigation of possibilities to manipulate the angular momentum transport in the magnetically ordered insulator by electrical means and by finite size effects. In addition, another goal is the enhancement of the sensitivity of the currently existing measurement setup and the realization of new measurement protocols in hard- and software.

An ambitious master student with good analytical skills is required to carry out these experiments on all-electrical magnon transport. One part of the thesis is the fabrication of nanometer sized devices for the experiments via electron beam lithography and UHV sputtering. The properties of these devices will be analyzed using magnetotransport experiments in superconducting magnet cryostats. Another important aspect is the realization of more sophisticated measurement methods, aiming for a enhancement in sensitivity, a better signal-to-noise ratios and a higher versatility of the measurement protocols

geeignet als
  • Masterarbeit Physik der kondensierten Materie
  • Masterarbeit Applied and Engineering Physics
Themensteller(in): Rudolf Gross
Heterostrukturen aus ferrimagnetischen Isolatoren und nichtmagnetischen Metallen für Experimente zu reinen Spin-Strömen

A fascinating manifestation of spin physics in the solid state are pure spin currents. Their generation and detection is often based on the interconversion of spin and charge currents in ferromagnetic insulator/normal metal heterostructures. The aim of this thesis is the fabrication of high-crystalline thin film heterostructures using reflection high energy diffracton (RHEED) assisted laser molecular beam epitaxy (laser-MBE) as well as electron beam physical vapor deposition. The thin film samples will then be characterized structurally using high-resolution X-ray diffractometry (HR-XRD) as well as magnetically via superconducting quantum interference device (SQUID) magnetometry. By using the best heterostructures, spin Hall magnetoresistance as well as spin Seebeck experiments will then be performed to investigate their spin current properties.
This thesis provides deep insight into thin film technology, laser-MBE, HR-XRD, SQUID magnetometry as well as magnetotransport experiments.  An important aspect hereby will be the fabrication of high-crystalline thin film heterostructures with excellent interface qualities.


geeignet als
  • Bachelorarbeit Physik
Themensteller(in): Rudolf Gross
Oxidische Heterostrukturen für Experimenten mit reinen Spinströmen

In most experiments pure spin currents are generated and/or detected via the spin Hall and inverse spin Hall effect in heavy metals. These two effects crucial depend on the magnitude of the spin-orbit interaction. The goal of this thesis is to investigate spin Hall effects physics in oxide systems, where also large spin orbit interaction is prevailing like the transition metal oxides. Especially, the realization of epitaxial multilayers of a spin Hall active material and an oxide magnetically ordered insulator are a major task of this research project. Such epitaxial structures are of current interest to better understand the underlying physics of pure spin current transports in these heterostrcutures.

We are looking for an enthusiastic master student to work on this  pure spin current physics related project. A crucial part of the thesis is the growth of oxide multilayers using laser-MBE under in-situ growth monitoring. The properties of these multilayers will then be investigated by structural, magnetic and magnetotransport techniques. As a next step, the tunability of relevant spin transport properties via the growth conditions will be analyzed.

geeignet als
  • Masterarbeit Physik der kondensierten Materie
  • Masterarbeit Applied and Engineering Physics
Themensteller(in): Rudolf Gross
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