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Neutron polarimetry and its application to some rare-earth systems

Roberts, Trefor William; (1999) Neutron polarimetry and its application to some rare-earth systems. Doctoral thesis (Ph.D), UCL (University College London). Green open access

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The salient points in the theory of neutrons and neutron scattering with respect to the production and analysis of beams of polarised neutrons are reviewed. A technique for the manipulation of the vector polarisation of a beam of neutrons incident upon a scatterer, and the analysis of the vector polarisation of a scattered beam is explained in detail, along with a description of a device that facilitates it. The technique is known as neutron polarimetry and the instrument is called CRYOPAD (CRYOgenic Polarisation Analysis Device). A method for calibrating CRYOPAD is given and the successful implementation and testing of this method is demonstrated. Three studies which make use of neutron polarimetry to probe the magnetic effects in certain rare-earth systems are presented. 1. The magnetic structures of the rare-earth metal neodymium are reviewed. The results of a study of those structures occurring in zero applied magnetic field, made with neutron polarimetry, are presented and discussed. Conclusions about the directions of the magnetic moments in some of these structures and their evolution with temperature are drawn. A study using conventional neutron-diffraction of some of the magnetic structures observed in an applied magnetic field is described. 2. A conventional neutron-diffraction study of the applied magnetic field - temperature phase diagram of the intermetallic compound NdCu₆ is presented in addition to a review of previous work carried out on this system. Certain features of the scattering in zero applied magnetic field are then explored using neutron polarimetry. 3. A review of the magnetic structures of the rare-earth metal erbium is made. The potential of neutron polarimetry to act as a sensitive test of the theory proposed to explain these structures is discussed, and the results of a study that attempted to perform this test are presented.

Type: Thesis (Doctoral)
Qualification: Ph.D
Title: Neutron polarimetry and its application to some rare-earth systems
Open access status: An open access version is available from UCL Discovery
Language: English
Additional information: Thesis digitised by ProQuest.
Keywords: Pure sciences; Neutron polarimetry
URI: https://discovery.ucl.ac.uk/id/eprint/10106315
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