1. SPES: Elucidating the importance of spin-spin interactions as a tool for new approaches in ESR studies of materials
The electron spin represents a sensitive local probe of its environment due to its large magnetic moment (at least 680 times larger than the magnetic moment of a proton) and, thus, experiences strong/weak magnetic couplings with homo-/hetero-spins. These magnetic couplings can be thoroughly studied by electron spin resonance (ESR) spectroscopy. Various magnetic interactions, such as hyperfine, dipolar, exchange or spin-orbit couplings can be exploited to get the information about the structure and dynamics of the material almost in any aggregate state. However, there is another perspective of this issue: the understanding of electron spin interactions in principle allows controlling the magnetic properties of the observed system and tailoring of new multifunctional materials with desired properties, starting from the chemical synthesis. Within this project proposal, technical developments regarding pulsed/high frequency ESR spectrometers will be exploited in order to achieve new insight into the properties of the material under investigation. In parallel, using well-established concepts of ESR spectroscopy, the classical phenomenological description of spin-spin interactions will be re-evaluated so that new theoretical approaches, including new simulation techniques, can be developed.
Therefore, within this project proposal, selected open questions are to be addressed as a research goals:
a) how to control the electron spin decoherence in a solid material when nuclear spin bath dynamics is a determining factor. Here, the hyperfine interaction in terms of nuclear spectral diffusion is the main focus of interest. Experimental model systems in which this channel of electron spin phase memory time decay is dominant will be purposely chosen. Various dynamical decoupling techniques will be applied in order to deduced how the physical state of the solid matrix (glassy or crystalline) could be extracted from the phase memory time experiments;
b) how to describe magnetic interactions and ordering in the crystal structure of molecular magnets (metal-organic frameworks, coordination polymers, transition metal complexes);
c) how to get information about rotational and translational dynamics of paramagnetic molecules in liquid systems by taking fully into account the effects of hyperfine, exchange, and dipolar interactions on their ESR spectra.
These three non-trivial experimental tasks to be performed in amorphous, crystalline and liquid materials aim to extend the current limits of the existing theoretical models of electron spin-spin interactions. The expected goal is to extract as much as possible information from the ESR spectral analyses by proper manipulation and the control of the electron spin states in an ESR experiment and to possibly pave the way to influence the properties/design of materials.