[1] Lund Univ, S-22100 Lund, Sweden
[2] Philips Res Leuven, B-3001 Louvain, Belgium
[3] IMEC, B-3001 Louvain, Belgium
[4] CEA, Dept Rech Fondamentale Mat Condensee, F-38054 Grenoble 9, France
[5] Philips Res Labs, NL-5656 AA Eindhoven, Netherlands
[6] Univ Wurzburg, D-97074 Wurzburg, Germany
[7] Delft Univ Technol, Kavli Inst Neurosci, NL-2600 GA Delft, Netherlands
[8] IBM Res GmbH, Zurich Res Lab, CH-8803 Ruschlikon, Switzerland
[9] Qumat Technol AB, S-22224 Lund, Sweden
[10] Max Planck Inst Microstruct Phys, D-06120 Halle, Germany