1Department of Microelectronics and Electrical Engineering, Trinity College, Dublin 2, Ireland
2Department of Applied Mathematics and Theoretical Physics, The Queen's University of Belfast, Belfast BT7 1NN, Northern Ireland, UK
3Laboratoire de Magnétisme et Matériaux Magnétiques, CNRS, 1, Place Aristide Briand, 92195 Meudon, France
4Institute of Radio Engineering and Electronics, Vvedenski Square 1, Fryazino, Moscow Region, 141120, Russia
5School of Computer Applications, Dublin City University, Glasnevin, Dublin 9, Ireland
6Department of Pure Mathematics, The Queen's University of Belfast, Belfast BT7 1NN, Northern Ireland, UK