Joost J. A. M. van der Mullen
Department of Applied Physics, Eindhoven University of Technology, P. O. Box 513, 5600 MB Eindhoven, The Netherlands
J. M. de Regt
Department of Physics, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
J. Jonkers
Department ofPhysics, Eindhoven University ofTechnology P.O. Box 513,5600 MB Eindhoven, The Netherlands
F. P. J. de Groote
Department of Physics, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands