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Title: Compton scattering studies of spin and charge momentum densities
Author: Timms, David N.
ISNI:       0000 0001 3533 5837
Awarding Body: University of Warwick
Current Institution: University of Warwick
Date of Award: 1989
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The ground state electron density distribution can be determined from the Doppler broadening of Compton scattered radiation. It is shown that Compton scattering of unpolarised photons leads to a measurement of the total electron momentum density distribution whereas if circularly polarised photons are used, the electron spin dependent density distribution is isolated. The experimental work reported here illustrates both techniques. Directional Compton profile measurements of an iron nickel alloy, gallium arsenide and lead have been performed with 60keV and 412keV unpolarised 7-radiation and demonstrate the sensitivity of the Compton profile and related functions to changes in the valence electron density resulting from disorder (FeNi), bonding (GaAs) and relativistic effects (Pb). Revision of the data processing procedure has yielded an improvement in the profile symmetry of these results. A new spectrometer dedicated to magnetic Compton studies has been designed and constructed. It uses circularly polarised radiation obtained by viewing the tangent point of the Daresbury synchrotron wiggler line at a small inclination to the orbital plane. Magnetic Compton profile measurements of polycrystalline iron undertaken with 54keV circularly polarised synchrotron radiation (CPSR) show a larger central dip than predicted by band theory calculations of the electron spin dependent density distribution. Data on polycrystalline cobalt has also been obtained. A transmission scattering geometry and 60keV CPSR have been used to measure, for the first time, directional Compton profiles of the unpaired spin electrons in a single crystal of iron. Separation of the contributions from the majority and minority spin electrons provide a more critical test of band theory than is possible with polycrystalline results.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: QC Physics