1. Department of Condensed Matter Physics, Chelyabinsk State University, 454001 Chelyabinsk, Russia
2. Department for Functional Nanosystems and High Temperature Materials, National University of Science and Technology “MISiS”, 119049 Moscow, Russia
3. Faculty of Physics and Center for Nanointegration Duisburg-Essen (CENIDE), University of Duisburg-Essen, 47057 Duisburg, Germany