Ph.D. Positions
Development of computational procedures and computer programs for processing pulsed EPR data
Pulsed Electron Paramagnetic Resonance (EPR) methods are intensively used to investigated structure and dynamics of complex macromolecules containing unpaired electrons. Among these methods Pulsed Electron-Electron Double Resonance (PELDOR) also known as Double Electron-Electron Resonance (DEER) has emerged as a powerful technique to determine relative orientation and distance between macromolecular structural units on nanometre scale. For successful applications of pulsed EPR methods it is important to have tools enabling transformation of measured signals into structural information. The goal of this PhD project is to develop new effective computational procedures and computer programs for the processing of measured pulsed EPR data in order to extract structural and dynamical information from experiments. This goal also includes application of the developed computational methods to real experimental data obtained on the molecules tagged with spin labels.
Supervisor: doc. Petr Neugebauer
Investigation of quantum phase transitions via Electron Spin Resonance
Magnetism emerges in matter due to the presence of unpaired electronic spins and the interaction between them in a wide range of materials from oxides to molecular materials. The collective behavior of spins, also known as quantum entanglement of spins, is a very active area of research with application to communication and computation. Electron spin resonance (ESR) is a key technique that enables to investigate spin states and spin-spin interactions. It has been successfully applied to monomeric and dimeric spin systems for identifying quantum transitions between entangled phases by varying parameters such as the temperature or the orientation of an external applied magnetic field. The aim of this project is to identify suitable materials such as spin dimers of molecular nature and apply ESR spectroscopy to study quantum phase transitions in the high frequency (up to 1 THz) and high field (up to 16 T) regime.
Supervisor: doc. Petr Neugebauer
Magnetic switchable systems based on metal complexes
Switchable systems based on metal complexes able to change magnetic properties are highly attractive for sensor applications, new electronic devices, or active smart surfaces usable in materials providing high-density data storage. For these applications, the magnetic activity of metal complexes can be utilized and furthermore, it can be modulated by modification of their coordination, redox, electronic and ligand field properties. Three ways to obtain such function are to vary the ligand field strength, switching the coordination chemistry or switching the degree of coupling between two spin metal ions in the case of polynuclear compounds. The aim of the project is to synthesize bi- or multistable metal complexes incorporating switch regulation site in order to perform controlled spin change. Our systems will be characterized by different physical techniques: high field and frequency EPR and NMR spectroscopy, Mass spectrometry, SQUID and X-Ray crystallography.
Supervisor: doc. Petr Neugebauer
THz Frequency Rapid Scan Electron Spin Resonance Spectroscopy
Dynamic Nuclear Polarization (DNP) is a phenomenon, that can enhance greatly the NMR sensitivity (several hundred times at least). There are several mechanisms of DNP, though all of them result from the transferring of electron spin polarization (from special polarizing agents) to nucleus. This process is strongly dependent on the electron spin relaxation of the polarizing agent. However, due to the instrument limitations, the spin dynamics of polarizing agents is studied very poorly at frequencies above 100 GHz, especially at frequencies of 263, 329 and 394 GHz, which correspond to NMR proton frequencies of 400, 500 and 600 MHz, respectively.
Usually, the spin relaxation properties are studied using the pulsed method. Unfortunately, the nowadays level of microwave sources at THz frequencies, mostly in terms of output power, does not allow the implementation of the pulsed technique in the wide frequency range. For this reason, the Rapid Scan Electron Spin Resonance (RS-EPR) spectroscopy is the only possible technique for the investigation of spin dynamics at THz frequencies. In this project, PhD student will (i) develop and implement a technique of fast frequency sweeps into the high field/high frequency EPR spectrometer (ii) investigate the spin relaxation processes in different DNP polarizing agents in the wide frequency and temperature ranges.
Supervisor: doc. Petr Neugebauer
Spectroscopy of thin molecular films
Control over thin molecular films composed of single-molecule magnets or quantum bits is crucial in the development of novel electronic and magnetic devices. Their behaviour on surfaces is yet largely unexplored area. This PhD project will use the already existing high-vacuum chamber for thermal sublimation of thin films of coordination transition metal and lanthanide complexes. The student will work on the whole route from a bulk as-synthesised powder to a nanostructured thin film. The final goal is to be able to predict and evaluate the magnetic properties of such films by newly built high-frequency electron spin resonance spectrometer (HF-ESR). Additional surface-sensitive spectroscopic and microscopic methods such as X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and scanning electron microscopy (SEM) will be used to study prepared thin films. The student will communicate and perform tasks in international collaboration with research groups in the USA and Italy.
Supervisor: doc. Petr Neugebauer
Intercalation of magnetic systems between 2D materials
There is growing interest in understanding magnetism of materials combined with 2-dimensional materials such as graphene. In particular, the impact of magnetic materials intercalated between the 2D material and its supporting substrate has the potential for magnetic ordering and may lead to modification/control of magnetic properties. Additionally, a system of magnetic material + 2D material could potentially be monolithically integrated with other devices to create new, robust electronic functionalities. The objective of this project it to develop and carry out strategies of intercalating magnetic atoms and molecules using graphene or other 2D materials. The subsequent structures would then be characterized by a wide range of surface probes as well as high field and frequency electron spin spectroscopy and nuclear magnetic resonance techniques. The knowledge gained will then be used to develop predictive models of magnetism for the intercalant + 2D material/substrate. This work will be carried out in collaboration with the US Naval Research Laboratory and will have opportunities for on-site research.
Supervisor: doc. Petr Neugebauer
Coordination compounds showing the magnetic bi- or multistability
Proposed PhD project is oriented on the synthesis and characterization of magnetically active transition metal and/or lanthanide complexes showing specific magnetic phenomena like spin crossover effect, single molecule magnetism or single chain magnetism. Such coordination compounds exhibit magnetic bi- or multistability and in this sense are very attractive from the application point of view. Possible technological utilization might be in the case of high capacity memory devices, display technologies, spinotronics, contrast agents for magnetic resonance imaging etc.
PhD study will be focused on the advanced organic and coordination synthesis of mononuclear and polynuclear complexes of transition metals and/or lanthanides. New-prepared compounds will be characterized by analytical and spectral methods and magnetic properties will be studied by means MPMS SQUID.
Supervisor: doc. Petr Neugebauer
Development of Fourier Transform InfraRed Spectroscopy in High Magnetic Fields
Fourier Transform Infra-Red (FTIR) spectroscopy in high magnetic fields presents an ideal combination of experimental techniques that can probe and elucidate properties of the most advanced materials. This technique provides complementary information to the commonly used measurements of transport, magnetization, and thermodynamic properties. The aim of this PhD project is to develop a compact spectrometer for FTIR spectroscopy in the high magnetic field at CEITEC BUT. The developed spectrometer will be used to perform sensitive measurements on Single Molecule Magnets (SMMs), modern 2D materials or combination of both.
Supervisor: doc. Petr Neugebauer
Design of Multipurpose Sample Holder for THz Spectroscopy
The aim of this PhD project is to develop multipurpose non-resonant sample holder for broadband Electron Paramagnetic Resonance spectrometer based on THz rapid frequency scans (THz-FRaScan-EPR) as well as for Fourier Transform InfraRed (FTIR) studies. Thanks to the developed sample holder the THz-FRaScan-EPR spectrometer will allow multi-frequency relaxation studies of variety of samples ranging from oriented bulk (crystal) materials, over powdered samples to air sensitive samples and liquid solutions. Furthermore, the design should allow inserting samples from Ultra High Vacuum. The sample holder should primary operate at frequencies between 80 GHz to 1100 GHz, at temperatures from 1.8 K to 300 K and at magnetic field up to 16 T. The sample holder will be tested on variety of samples ranging from Single Molecule Magnets over modern 2D solid state materials to air sensitive biological samples.
Supervisor: doc. Petr Neugebauer
New generation of graphene bolometers
Since the discovery a few years ago that a single layer of graphite, graphene, could be mechanically exfoliated from larger crystals using scotch tape, there has been an upsurge of research on graphene and other materials with a layered crystallographic structure similar to graphene. The possibility to combine single-layer materials with different electronic properties into heterostructures with atomically sharp interfaces and the suitability for flexible substrates offer unprecedented opportunities for novel device architectures. The ideas can be realized thank to the progress in developing processes to grow large area, high quality, single-layer material since mechanical exfoliation is a slow process for research (although it provides high-quality layers) and it is indeed not suitable for commercial applications. Methods for large-area growth of graphene have been developed in the past few years and are now used by several groups. They include chemical vapor deposition (CVD) of graphene on copper or nickel foils and epitaxial synthesis via Si sublimation at the surface of SiC substrates. However, substantial area growth of monolayers of other layered materials is still a challenge, although methods to grow millimeter-size monolayer films of MoS2 by CVD have already been developed. Fabrication of high-quality large-area monolayers facilitates the systematic study of another particularly intriguing aspect of these materials, namely that the dimension of a monolayer can be further reduced from 2D to 1D or 0D by patterning it in the shape of nanoribbons or quantum dots. The realization of quantum confinement down to zero dimension indeed leads to exciting physics, and we will investigate if it can be used for practical applications. In this thesis, we will study how quantum confinement, achieved by nanopatterning these two-dimensional (2D) materials can yield novel high-performance devices.
Supervisor: doc. Petr Neugebauer
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