Materials, minerals and magnetism as seen by solid-state NMR and other techniques

General ILL Seminar
Organised by College 4

Friday, 24 February 2020 at 11:00
Seminar room (no 163), ILL 4

Professor Ulla Gro Nielsen
University of Southern Denmark – Odense - Denmark

Abstract

The function of catalytic and magnetic materials, which are often inspired by minerals, rely on the flexible oxidation state and magnetic properties. However, the presence of structural defects, disorder and often complex composition affects these properties. These can be probed by solid state NMR spectroscopy (SSNMR) to obtain insight into the local structure and magnetic interaction.  
Jarosites (AB3(SO4)2(OH)6) with A = K, Na, and H3O and B = Fe(III), V(III), and Cr(III)  are a classic example of frustrated magnetic systems with a 2D so-called Kagomé lattice. They are notorious for their non-stoichiometric composition, which have led to ambiguities about their magnetic properties. Variable temperature 2H MAS NMR in combination other techniques served as a probe of the local magnetic properties and defect structure.
Calculation of NMR parameters for paramagnetic systems is challenging due to presence of multi-configurational ground states and low-lying excited state. We have investigated a series of metal acetyl acetonates complexes with different metal ions (V(IV), V(III), Ni(II), and Cu(II)] by 1,2H and 13C SSNMR and quantum chemical calculations of NMR parameters to understand how the choice of magnetic ion affect the magnetic properties. This provided detailed insight into the different contribution the different factors contributing to the paramagnetic shifts and allowed for spectral assignment of these complexes.

Lucile Mangin-Thro

College 4 Secretary

External visitors may ask for a site access to Brigitte Dubouloz (dubouloz@ill.eu)