Exploring the Nuclear Magnetic Resonance (NMR) technique as tool for modern materials research

• Applicant: Dr. Sabine Wurmehl
• Subject Area: Experimental Condensed Matter Physics ; Physical Chemistry of Solids and Surfaces, Material Characterisation
• Term: from 2018 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 397409592

One of the major challenges in modern materials research is the understanding and control of structure-property-relationships in order to tailor specific properties of functional (magnetic) materials. This fact requires a thorough analysis of structure and in response of the (magnetic) properties, and is, in particular, to be addressed if the structure of a given material is modified with the aim to control the properties, e.g. by annealing, ion irradiation, substitution of constituents or by downscaling to yield nanoscale objects.This project aims to explore the power of NMR as sophisticated method to study structural, magnetic and electronic structure modifications of selected functional magnetic materials on a local scale and to further advance the NMR method. During this project we will explore NMR as tool to monitor changes in the material; we will use four selected parameters to modify structure and properties to challenge the NMR technique: (i) we will apply ion beam irradiation to alter chemical order and in response the magnetic properties of different functional intermetallic materials showing high spin polarization (Co2MnSi), a strong interaction between structure and magnetic properties (Fe60Al40) and magnetocaloric properties (Fe-Rh). The impact of ion irradiation is local and difficult to be studied by e.g. XRD, we will explore to which extend NMR will be able to resolve the structural modifications upon irradiation (aim 1), (ii) we will study the impact of annealing on the structural properties of MnN film stacks. Here, we combine three advances of NMR, namely, we will study the (local) structure of both MnN and the adjacent Co-Fe layer, we will investigate the local magnetic properties by rf power dependencies and we will shed light on the interface between MnN and Co-Fe (aim 2), (iii) we will investigate the evolution of properties and in particular the half-metallic ground state in a substitution series on the of Co2MnAlxSi1-x, revealing whether there is a statistical distribution of host and substitution atoms, we will learn whether additional disorder plays a role and we will measure the changes in the electronic structure upon substitution (aim 3). (iv) We will downscale magnetic intermetallic materials to the nanoscale and explore the power and limits of NMR to study their properties in response to their downsizing (aim 4).Nuclear magnetic resonance (NMR) is a versatile and sensitive lab-based method to encounter the problem of investigating detailed structural, electronic and magnetic property changes as outlined above. We expected to challenge the NMR technique to study functional magnetic materials relevant for modern materials research.

• DFG Programme: Research Grants