Polak, Sergiusz (2025) Symmetry Analysis of Non-Collinear Antiferromagnets. Bachelor's Thesis, Mathematics.
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Abstract
Altermagnets - antiferromagnets exhibiting responses typical of ferromagnets, have recently emerged as a promising platform for spintronic devices. Spin groups are often used to analyze alter- magnets, as unlike magnetic groups, they distinguish non-relativistic effects independent of spin-orbit coupling (SOC). In this study, the representation theory of spin point groups and mag- netic point groups is used to analyze the occurrence of the anomalous Hall effect (AHE), T -odd spin Hall effect (SHE), and spin-splitting of electron bands in selected non-collinear antiferromagnets Mn3X (X = Ir, Ge, Sn) , Mn3NiN, and MnTe2. The allowed components of the tensors describing these effects are explicitly determined, both in the presence and absence of SOC. The study demon- strates a link between T -odd SHE and spin splitting of bands quadratic in the wavevector ⃗k. The calculations demonstrate that all of the analyzed materials permit SOC-free T -odd spin Hall effect and quadratic spin splitting, while Mn3X and Mn3NiN allow AHE and a weak ferromagnetic mo- ment with SOC. Furthermore, the study determines all the allowed components of the T -odd spin conductivity tensor with and without SOC, and by extension, the allowed quadratic spin-splitting terms, as well as enumerating the quartic and sextic spin-splitting terms with or without SOC for the analyzed materials. The results agree with the experiments and demonstrate the effectiveness of a representation theory approach.
| Item Type: | Thesis (Bachelor's Thesis) |
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| Supervisor name: | Waalkens, H. and Mostovoy, M.V. |
| Degree programme: | Mathematics |
| Thesis type: | Bachelor's Thesis |
| Language: | English |
| Date Deposited: | 16 Jul 2025 07:31 |
| Last Modified: | 16 Jul 2025 07:31 |
| URI: | https://fse.studenttheses.ub.rug.nl/id/eprint/36072 |
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