Synthesis and Magnetic Studies of Quasi-Isotropic Coordination Compounds with 3d and 4f cations
[eng] The present Thesis is entitled “Synthesis and Magnetic Studies of Quasi-Isotropic Coordination Compounds with 3d and 4f cations”. The topic of the Thesis is to prepare coordination compounds of paramagnetic metal cations, either 3d or 4f, with Schiff base ligands, in order to study their magne...
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| Tipo de recurso: | tesis doctoral |
| Estado: | Versión publicada |
| Fecha de publicación: | 2023 |
| País: | España |
| Institución: | Universidad de Barcelona |
| Repositorio: | Dipòsit Digital de la UB |
| OAI Identifier: | oai:diposit.ub.edu:2445/202521 |
| Acceso en línea: | https://hdl.handle.net/2445/202521 http://hdl.handle.net/10803/689085 |
| Access Level: | acceso abierto |
| Palabra clave: | Magnetisme Compostos de coordinació Lantani Magnetism Coordination compounds Lanthanum |
| Sumario: | [eng] The present Thesis is entitled “Synthesis and Magnetic Studies of Quasi-Isotropic Coordination Compounds with 3d and 4f cations”. The topic of the Thesis is to prepare coordination compounds of paramagnetic metal cations, either 3d or 4f, with Schiff base ligands, in order to study their magnetic properties and their slow relaxation of magnetization (SRM). The main characteristic of the compounds that show SRM is the presence of magnetic anisotropy, in the form D or axial zero-field splitting, which define the energy barrier that has to be overcome in order to have relaxation of magnetization. This Thesis provide experimental evidence that even if the parameter D can take low values, or even negligible, SRM can happen. This kind of systems belong the family of quasi-isotropic SMMs, because they have as building blocks metal cations that possess very small magnitude of D. The cations that have been chosen for this research are GdIII and MnII, which contain half- filled f and d orbitals, respectively. GdIII cannot present magnetic anisotropy due to its spherical electronic configuration; MnII has no crystal field stabilization energy, and thus, allowed us to tune its geometry. This fact, helped in order to prove that firstly, low magnetic anisotropy can play a pivotal role for the presence of SRM and secondly, that geometric distortions in cation’s environment are desired in order to observe relaxation of magnetization. Due to the fact that magnetic anisotropy takes very low values, classical magnetometry cannot give reliable results. Thus, Electronic Paramagnetic Resonance (EPR) measurements were carried out in order to define the axial and rhombic values of anisotropy. |
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