1. Magnetism Division, Faculty of Physics, M. V. Lomonosov Moscow State University, Leninskie Gory, Moscow 119992, Russia
2. Optical and Semiconductor Devices Group, Electrical and Electronic Engineering (EEE) Department, Imperial College, Exhibition Road, London SW7 2BT, United Kingdom
3. University of Oxford, Department of Engineering Science, Parks Road, Oxford OX1 3PJ, United Kingdom