ACKNOWLEDGEMENTS

As numerous people have given immeasurable amounts of time and effort over the last three years, without whom this PhD could not have happened, I would like to take this opportunity to thank all those who have helped me. Firstly, I would like to thank my supervisor Peter de Groot for giving me the opportunity to do this thesis research, and his guidance during the last three years.
Secondly, I would like to thank some members of the Magnetism and Superconductivity group to which I belonged for all the help and encouragement that they gave me: namely Graham Bowden (particularly for rendering my English writing more English, and much less French), Sergey Gordeev (for the numerous corrections he brought to my attention, all the advice and explanations that he patiently gave me), and Sasha Zhukov (for the stimulating discussions about magnetism). I must acknowledge that the work done could not be carried out without the active collaboration of the Oxford MBE Group, led by Drs. M. Wells and R. Ward.
This work was supported by QinetiQ (former DERA) at Farnborough (UK). I thank Dr. G. J. Tomka (QinetiQ) for useful discussions.
I also want to thank my family for their constant support. Finally, I must thank a couple of very interesting people I met during my PhD: Donald Kahari, Emanuele Di Nicolo, Mamadou Bah, Clarence Chongo, Teddy Chungu and Mathew Mwanza.
Also, I would like to thank some French fellows for having lived with me through my two last years PhD, good and bad times: Floriane Bozon, Mia Komen, Coralie Lagrange, Melissa Remoue, Frantz Leroy.