1. Wolfson Centre for Magnetics, Cardiff School of Engineering, The Parade, Cardiff University, Cardiff CF24 3AA, UK
2. School of Engineering and Materials Science, Queen Mary University of London, Mile End Rd, London E1 4NS, UK
3. Nanoforce Technology Ltd., Joseph Priestley Building, Queen Mary, University of London, Mile End Road, London E1 4NS, UK
4. Institute of Mechanical and Manufacturing Engineering, Cardiff School of Engineering, Cardiff University, The Parade, Cardiff University, Cardiff CF24 3AA, UK