Ferromagnetic (Ga,Mn)As Layers and ... - OPUS Würzburg

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106 Publications • B. Schmid, A. Müller, M. Sing, R. Claessen, J. Wenisch, C. Gould, K. Brunner, L. W. Molenkamp, and W. Drube, Surface segregation of interstitial manganese in Ga 1−x Mn x As studied by hard X-ray photoemission spectroscopy, Phys. Rev. B 78, 075319 (2008). • M. Ghali, T. Kuemmell, J. Wenisch, K. Brunner, and G. Bacher, Electrical charging of a single quantum dot by a spin polarized electron, Appl. Phys. Lett. 93, 073107 (2008).
Acknowledgements There is a number of people which were involved in some way with my work in Würzburg to whom I want to express my gratitude. • First of all, I want to thank my supervisor Prof. Karl Brunner for accepting me in this position and always having an open ear for helpful discussions. The freedom to try out my own ideas and actively steer the direction of this work has been a great experience. • Thanks to Prof. Laurens Molenkamp, Dr. Georg Schmidt and Dr. Charles Gould for the highly interesting and fruitful cooperation in the spintronics group. • Special thanks to two of my colleagues, Andreas Benkert and Suddhasatta Mahapatra. It has not only been a very enlightening and genial experience to work with you. I will also gladly remember the good times spent together away from work. • Thanks to my former diploma student and now successor Lars Ebel for a great cooperation and for taking quite some workload off my shoulders at times. • Thanks to my predecessor Gisela Schott for teaching me a lot about MBE in my first months and for handing over to me such a well maintained and excellently documented chamber. • Thanks to Claus Schumacher and Volkmar Hock for teaching me countless small things around the clean room and MBE labs. • Thanks to all Alfred Schönteich and all the people in the electronics and mechanics workshop for fixing various things that got broken, which is not exactly a rare occurrence in the MBE business. • Also thanks to Petra Wolf-Müller and Anita Gebhardt for a few hundred prepared samples and being such pleasant people to share a room with. • Thanks to Manuel Schmidt for his contribution to the theoretical parts of this work. • And finally a big thanks to all the colleagues at EP3, it has been a great atmosphere here. Special thanks to Charles Gould, Kathrin Pappert, Gabriel Dengel, Stefan Mark, Tobias Kießling, Marcel Zimmermann, Jan Storz, and Jean de Zélicourt for their contribution to this work in the form of numerous measurements on my samples. 107
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Ferromagnetic (Ga,Mn)As Layers and
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Contents Zusammenfassung 5 Summary
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Zusammenfassung Ferromagnetische Ha
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Anisotropiekontrolle in (Ga,Mn)As i
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Summary The great promise of ferrom
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Chapter 1 Introduction The event co
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13 investigated with SQUID and magn
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Chapter 2 The (Ga,Mn)As Material Sy
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2.1. Ferromagnetism in (Ga,Mn)As 17
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2.2. Band Structure Calculations in
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2.3. Magnetic Anisotropy 21 growth
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2.3. Magnetic Anisotropy 23 E n e r
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2.3. Magnetic Anisotropy 25 Figure
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Chapter 3 MBE Growth of Ferromagnet
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3.2. Epitaxial Growth of (Ga,Mn)As
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3.3. Crystal Defects 31 lead to a d
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3.4. RHEED 33 Figure 3.5: (a) Ewald
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3.5. X-Ray Diffraction 35 1 0 7 1 0
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3.5. X-Ray Diffraction 37 between t
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3.5. X-Ray Diffraction 39 lattice d
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3.5. X-Ray Diffraction 41 substrate
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Chapter 4 Finite Element Simulation
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4.1. Derivation of the Equation Sys
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4.2. The FlexPDE Software 47 4.2 Th
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4.3. Simulation Results - Physical
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Page 55 and 56: 4.4. Simulation Results - (In,Ga)As
Page 57 and 58: 4.5. Stripes Along [1¯10] 57 Figur
Page 59 and 60: 4.5. Stripes Along [1¯10] 59 in-pl
Page 61 and 62: Chapter 5 Local Anisotropy Control
Page 63 and 64: 5.1. Patterning and Structural Char
Page 73 and 74: 5.2. Magnetic Characterization 73 p
Page 75 and 76: 5.2. Magnetic Characterization 75 1
Page 77 and 78: 5.2. Magnetic Characterization 77 8
Page 79 and 80: 5.3. Shape Anisotropy 79 ∼ 0.2 k
Page 81 and 82: 5.4. A Model for Anisotropy Orienta
Page 83 and 84: 5.4. A Model for Anisotropy Orienta
Page 85 and 86: Chapter 6 Device Application As sta
Page 87 and 88: 6.2. The Role of the Constriction 8
Page 93 and 94: Chapter 7 Conclusion and Outlook Th
Page 95 and 96: Appendix A Band Structure Hamiltoni
Page 97 and 98: Appendix B Sample FlexPDE Input Fil
Page 99 and 100: 99 BOUNDARIES s u r f a c e ’ s u
Page 101 and 102: Bibliography [Abol 01] M. Abolfath,
Page 103 and 104: 103 [McGu 75] T. R. McGuire and R.
Page 105: Publications • J. Wenisch, C. Gou
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