This thesis investigates some aspects of the ordering of nuclear spin systems at low temperatures. The thesis is divided into two parts. In part one some nuclear orientation experiments of <sup>74</sup>As in Fe and <sup>206</sup>Bi and Ni and Fe are described. These nuclei are orientated by the large hyperfine field inside Ni and Fe. The orientation is detected by the anisotropy of the emitted gamma-rays and in the case of <sup>74</sup>As by the destruction of this anisotropy by NMR. Chapter one reviews the theory of the nuclear orientation method. To aid in the interpretation of the <sup>206</sup>Bi results, some channelling experiments were done. A review of the method of atom location by channelling is given in chapter two. Chapter three describes the apparatus and technique used. The results of the <sup>74</sup>AsFe experiments are given in chapter four. In these experiments the magnetic moment of the ground state of <sup>74</sup>As was measured to be μ = 1.597(3), the sign of the hyperfine field was found to be positive, and the spin-lattice relaxation time was found to be 120(30) s. The results of the <sup>206</sup>BiNi experiments are given in chapter five. The hyperfine was found to be 390(15) kOe for both diffused polycrystalline and implanted single crystal samples. The multipolarity mixing ratios of many of the gamma,-rays were found. Reorientation of the metastable state of <sup>206</sup>Pb was observed, which had not been expected. On the basis of the channelling experiments, this reorientation has been explained by the theory.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:463416 |
| Date | January 1973 |
| Creators | Llewellyn, Graeme Ernest John |
| Contributors | Corden, W. M. |
| Publisher | University of Oxford |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://ora.ox.ac.uk/objects/uuid:7fe6e361-6ccf-4be3-8223-cec272d03597 |
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