Use this URL to cite or link to this record in EThOS:
Title: Magnetism in frustrated magnets revealed by neutron polarimetry
Author: Poole, A. L.
ISNI:       0000 0004 2729 4328
Awarding Body: University College London (University of London)
Current Institution: University College London (University of London)
Date of Award: 2011
Availability of Full Text:
Access from EThOS:
Access from Institution:
The work in this thesis uses neutron polarimetry and representational analysis to illuminate complex magnetic structures. The combination of these techniques is particularly suited to examining magnetic materials that have frustrated magnetic order and domain structures. The materials that are investigated in depth are Er2Ti2O7 and MnWO4. Er2Ti2O7 is a member of the pyrochlore family of materials and exhibits the classic signs of geometric frustration. The material has been proposed as an XY antiferromagnet that selects a specic basis vector ground state due to an order-by-disorder transition. The previous experimental work could not fully determine the precise details of the ground state and hence was not able to fully conrm the proposed theory. The structure was examined using neutron polarimetry and representational analysis to try and determine the magnetic order at low temperature. MnWO4 is an example of a magnetic material with complex order and frustration that arises due to competing exchange interactions. The material has a cycloidal magnetic structure that breaks the inversion symmetry and gives rise to dierent k-domains. The population of these dierent domains is intrinsically linked to the electronic polarization of the material, such that when one domain is populated MnWO4 has a spontaneous electric polarization and is belongs to the multiferroic family of materials. By using representation analysis the number of parameters that is required to describe the magnetic structure is greatly reduced and the link between inversion symmetry breaking and multiferroicity may be better understood. This thesis aims to identify the structures of both Er2Ti2O7 and MnWO4 as well as develop the interpretation of the polarimetry techniques.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available