The work on this thesis has been an inspiring, often exciting, sometimes challenging, but always interesting experience. It has been made possible by many other people, who have supported me.
I am very grateful to my supervisor Josef Fidler who has given me the chance to participate in several interesting research projects and attend various international conferences. He has supported me with his encouragement and many fruitful discussions. I would also like to express my sincere thanks to Thomas Schrefl for his invaluable experience and advice. The close cooperation with Thorsten Matthias, Dieter Süss, Hermann Forster, Rok Dittrich, and Vassilios Tsiantos as well as many other students was a great experience, which lead to many joint publications. The internship at Seagate Research in Pittsburgh was a unique experience and I would like to thank Roy Chantrell, head of the theory group, for this great opportunity.
Finally, I wish to thank my parents for their continuous support and encouragement.
Support by the following projects is thankfully acknowledged: