de | en

Dr. rer. nat. Sebastian Mühlbauer

Lehrveranstaltungen und Termine

Ausgeschriebene Angebote für Abschlussarbeiten

Schalten von Domänen mit Hilfe von elektrischen Feldern in multiferroischem Ba2CuGe2O7

Certain magnetically ordered materials are characterized by a non-collinear arrangement of the spins: In particular helimagnets but also other incommensurate and/or chiral spin structures have recently regained tremendous interest – partially due to their multiferroic properties, where ferroelectric and ferromagnetic order are closely coupled. This coupling could be ideally exploited for the use in future electronic, logical or data storage devices.
The purpose of this project is to use neutron scattering and complementary bulk measurement techniques to study the multiferroic compound Ba2CoGe2O7, where a cycloidal magnetic order is observed as a ground state below 3.2 K.
The proposed bachelor thesis covers the use of a dedicated sample stick which enables the application of high electrical fields to the sample in order to switch the magnetic domain state. The switching will be observed by means of neutron scattering experiments.  This thesis requires the preparation and characterization of the single crystal sample by means of X-ray Laue diffraction and measurements of the susceptibility, the preparation of the sample stick and the execution of the neutron scattering experiment including the subsequent data analysis. A solid background in solid state physics, in particular magnetism, but also mechanical skills are required. The work will be performed together with the SANS-1 team @ MLZ and offers the unique possibility to get hands on experience at an internationally leading large scale neutron facility like the MLZ.

Contact: Dr. Sebastian Mühlbauer, sebastian.muehlbauer@frm2.tum.de, 089 289 10784

geeignet als
  • Bachelorarbeit Physik
Themensteller(in): Peter Böni
Simulation von Flussliniengittern in Supraleitern mit Hilfe von Molecular-Dynamics Simulationen

A superconducting vortex consists of a normal conducting core carrying the magnetic field, screened by a superconducting current. The macroscopic continuity of the wavefunction of the cooper pairs leads to the quantization of flux and renders superconductivity a textbook example of a macroscopic quantum effect. Therefore, superconducting vortices resemble countable, impartible entities that can be assigned with particle-like properties which take over the role as building blocks of a novel kind of matter denoted “vortex matter”. Similar to atoms that condense to a crystal also the superconducting vortices arrange themselves in a vortex lattice which corresponds to a two-dimensional Bravais lattice, reflecting the minimal free energy landscape, where a regular hexagonal symmetry is obtained for isotropic superconductors within the Ginzburg-Landau theory.
Analogous to condensed matter a large variety of phases is also observed for vortex matter. Besides long range ordered vortex lattices, vortex glasses and vortex liquids have been identified. Vortex matter is governed by a multitude of different interactions on the vortices: The energy associated with the expulsion of the magnetic flux leads to a repulsive interaction, while for some superconducting materials, the reduction of energy of overlapping vortex cores can lead to a long range attractive force.
Using neutron scattering, we have carefully examined the phase transitions and domain formation processes of the vortex lattice in the model superconductor Niobium. Topic of this Bachelors thesis is to develop and implement 2D molecular dynamic simulations of superconducting vortex matter. The phase transitions and the domain formation process of the vortex matter shall be simulated considering the various inter-vortex interactions, the presence of pinning and the influence of temperature and magnetic field. The results of the simulations can be directly compared to and fitted to the existing experimental data.
These tasks require both a strong interest in programming and a solid background in condensed matter physics, in particular superconductivity.
The work will be performed together with the SANS-1 team @ MLZ and offers the unique possibility to work at an internationally leading large scale neutron facility like the MLZ.

Contact:
Dr. Sebastian Mühlbauer, sebastian.muehlbauer@frm2.tum.de, 089 289 10784
Alexander Backs, alexander.backs@frm2.tum.de, 089 289 54825

geeignet als
  • Bachelorarbeit Physik
Themensteller(in): Peter Böni
TISANE: Anwendung zeitaufgelöster Kleinwinkelstreuung zur Untersuchung der dynamischen Eigenschaften in Ferrofluiden

Small-angle neutron scattering (SANS) is a powerful technique to study correlations of condensed matter samples in the range of 20–2000 Å. As an extension of a standard SANS setup, TISANE (Time Involved Small Angle Neutron Scattering) is a new neutron scattering technique for time resolved kinetic neutron scattering. TISANE is able to resolve dynamic processes up to microsecond time-scales. The setup is based on two counter-rotating chopper disks installed at a standard small angle neutron scattering beamline.
Such a TISANE setup has recently been installed at the SANS-1 beamline at MLZ, jointly operated by TUM and Helmholtz Zentrum Geesthacht. An AC-field setup allows to apply AC fields up to 10 kHz and static fields to the sample, providing an ideal tool for the investigation of the dynamical properties of ferrofluid samples. A ferrofluid is a colloidal liquid made of nanoscale ferromagnetic particles in a carrier fluid. Ferrofluids are used for various applications like damping, speakers, liquid sealings but also in cancer therapy.
The task of this Bachelors thesis is the characterization of ferrofluid samples on a time-scale up to 10 kHz by means of time-resolved small angle neutron scattering. It includes the preparation of the samples, their characterization by means of measurements of susceptibility and magnetization, the neutron experiment and the subsequent data analysis. A solid background in solid state physics, in particular magnetism, but also mechanical skills are required. The work will be performed together with the SANS-1 team @ MLZ and offers the unique possibility to get hands on experience at an internationally leading large scale neutron facility like the MLZ.

Contact: Dr. Sebastian Mühlbauer, sebastian.muehlbauer@frm2.tum.de, 089 289 10784

geeignet als
  • Bachelorarbeit Physik
Themensteller(in): Peter Böni
Nach oben