Antiferromagnetic Wheels Probed by Inelastic Neutron Scattering.

Abstract

Magnetic molecules are of interest for their potential application in quantum computing and fundamental physical properties. For both of these research justifications there is clearly large overlap; the identification of suitable model systems to test or apply theoretical models. As the theoretical models become more intricate and complex, accurate characterisation is of upmost importance. This thesis demonstrates methods for detailed characterisation of a closely related group of chromium(III) antiferromagnetic (AF) wheel clusters. This group of systems are selected for their interesting magnetic properties including, frustration and anisotropy effects. Controlled molecular variation is also of interest, such as the insertion of dopant metal ions into homometallic wheels, and the variation of capping ligand on the ends of wheel segments. Inelastic neutron scattering (INS) provides a highly sensitive method to perform these investigations. Following recent development of the IN5b spectrometer at the Institut Laue-Langevin, Grenoble, new limits for what can now be measured are explored. A method for measuring large portions of vectorial neutron momentum transfer space, for inelastic energy transfers, is tested. It is demonstrated in a single crystal INS study on a Cr8Mn wheel, that dynamic spin correlations can be measured, without the requirement of a spin Hamiltonian model. This result is significant for magnetic clusters with a too large Hilbert space to be characterised by a spin Hamiltonian model.

Date of Award	1 Aug 2011
Original language	English
Awarding Institution	The University of Manchester
Supervisor	David Collison (Supervisor), Eric Mcinnes (Supervisor) & Richard Winpenny (Supervisor)