III-Mn-V dilute ferromagnetic semiconductors (DFSs) have been treated as a candidate material for semiconductor spintronics due to their intrinsic ferromagnetism mediated by holes.
In this thesis, three different Mn doped III-V DFSs, (In,Mn)As, (Ga,Mn)As, and (Ga,Mn)P, have been produced by ion implantation and pulsed laser melting. The comparison of magnetic anisotropy, magnetization, Curie temperature, as well as the electrical property is performed between three different materials to understand the nature of hole-mediated ferromagnetism in DFSs.
An in-plane magnetic easy axis is observed in (Ga,Mn)As and (Ga,Mn)P, while an out-of-plane magnetic easy axis is found in (In,Mn)As due to the contribution of different inner strain resulting from the lattice mismatch between the DFS layer and the corresponding substrate. Most importantly, the direct proof of interplay between localization and magnetism is provided by a systematic comparison between (Ga,Mn)As and (In,Mn)As. When the Mn concentration is increased in the regime of the insulator-metal transition, the long-range ferromagnetic coupling is gradually built up accompanied with the appearance of metallic features. The generation of long-range global ferromagnetism is strongly influenced by the p-d coupling between hole and Mn local spins: The global ferromagnetism (metallic feature) happens at lower Mn concentration in (In,Mn)As than in (Ga,Mn)As due to the stronger p-d coupling from the smaller lattice parameter of GaAs. Moreover, for the case of (Ga,Mn)P with the strongest p-d coupling in comparison with (In,Mn)As and in (Ga,Mn)As, the super-exchange model has to be considered, since metallic features does not appear at the highest obtainable Mn concentration.
Through the comparison between three different DFS materials, our findings strongly advocate for the heterogeneous model of electronic states at the localization boundary and point to the crucial role of weakly localized holes in mediating efficient spin-spin interactions even on the insulator side of the insulator-metal transition at least for (In,Mn)As and in (Ga,Mn)As.
| Identifer | oai:union.ndltd.org:DRESDEN/oai:qucosa.de:bsz:14-qucosa-232203 |
| Date | 10 January 2018 |
| Creators | Yuan, Ye |
| Contributors | Technische Universität Dresden, Fakultät Mathematik und Naturwissenschaften, Prof. Dr. Manfred Helm, Dr. Shengqiang Zhou |
| Publisher | Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden |
| Source Sets | Hochschulschriftenserver (HSSS) der SLUB Dresden |
| Language | English |
| Detected Language | English |
| Type | doc-type:doctoralThesis |
| Format | application/pdf |
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