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Title: | Quasi Two Dimensional Magnetic Properties of the Tri-Rutile Phases MTa₂O₆, M = V, Fe, Co, Ni |
Authors: | Eicher, Maria Sonja |
Advisor: | Greedan, J.E. |
Department: | Chemistry |
Keywords: | Chemistry;Chemistry |
Publication Date: | Dec-1984 |
Abstract: | <p>The structural and magnetic properties of the tri-rutile phases MTa₂O₆ (M = V, Fe, Co, Ni) were investigated. The nuclear and magnetic structures were refined from neutron powder diffraction data. The magnetic M²⁺ ions are located in planes perpendicular to the c axis. The distance between neighboring planes is approximately 4.5 Å. As a result, these compounds are quasi two dimensional magnetic systems, because the magnetic exchange interaction between ions in (001) planes is much larger than the interaction between ions in neighboring planes.</p> <p>Evidence for important two dimensional correlations has been obtained from magnetic susceptibility and heat capacity measurements. The magnetic susceptibility of these materials is characterized by a broad maximum at a temperature substantially above the ordering temperature. The experimentally observed magnetic susceptibility was compared to the predictions for 2-d quadratic layer models. The exchange interaction was antiferromagnetic in all cases. NiTa₂O₆ and VTa₂O₆ are Heisenberg systems with S = 1 and S = 3/2, respectively. The magnetic susceptibility of CoTa₂O₆ was consistent with an S = 1/2 Heisenberg model, while FeTa₂O₆ showed Ising-like behavior with S = 11.2.</p> <p>The magnetic structures of FeTa₂O₆ and VTa₂O₆ were determined. Mössbauer effect measurements were used to distinguish between two possible structural models for FeTa₂O₆. The magnetic moments of the Fe²⁺ ions points along <110> directions. The magnetic structure of VTa₂O₆ is similar, but the V²⁺ moments are oriented along <001>.</p> |
URI: | http://hdl.handle.net/11375/5914 |
Identifier: | opendissertations/1256 2442 1298168 |
Appears in Collections: | Open Access Dissertations and Theses |
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