The RMn6T6-xXx family of compounds (R = rare earth; T = Ge, Sn; X = Ga, In) has seen a lasting and intensive series of studies over the past several years. In these systems, a spin reorientation process, which is a pure rotation of the magnetic structure relative to the crystal axes, can be used to determine the anisotropic contributions to the transferred hyperfine fields at the Sn sites. The anisotropic contribution has been shown to be substantial in the MnSn2 and FeSn2 compounds, and is an important fraction of the overall transferred hyperfine field. A spin reorientation transition can be either temperature-induced, or field-induced (spin-flop). The temperature-induced spin reorientation generally results from a competition between the magnetocrystalline anisotropies of the rare earth and Mn sublattices. The substitution of Sn with Ga strongly affects the anisotropy, shown here to decrease the spin reorientation temperature with increasing x by 255 +/- 18 K/Ga in TbMn6Sn 6-xGax. However, the sublattice anisotropies seem unaffected by In substitution, and the spin reorientation temperature is nearly constant throughout a large range of In concentration. A field-induced spin-flop can be achieved by applying a large enough field perpendicular to the direction of the moments. / In this study, we show how both the temperature-induced SR and field-induced SF allow for the anisotropic field to be isolated from the isotropic contribution. The consistency between the two measurements of the anisotropic field indicates that the magnitude of the anisotropic contribution is independent of the driving force of the reorientation. We show that a complete 90° spin reorientation occurs in the ErMn6Sn5.89Ga0.11 and TbMn 6Sn6-xGax compounds (0.2 ≤ x ≤ 0.8), as well as in TbMn 6Sn5.46In0.54 at room temperature for an applied field of 0.57(3) T. The site preference for Ga substitution is investigated and compared with former results. Finally, the anisotropic contribution at one of the Sn sites is shown to exceed 40% in all of the compounds investigated, and this site assignment is confirmed.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.98767 |
| Date | January 2006 |
| Creators | Perry, Laura Katherine. |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Master of Science (Department of Physics.) |
| Rights | © Laura Katherine Perry, 2006 |
| Relation | alephsysno: 002481658, proquestno: AAIMR24768, Theses scanned by UMI/ProQuest. |
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