1. Key Laboratory of Magnetic Molecules and Magnetic Information of Ministry of Education School of Chemistry and Material Science Shanxi Normal University Taiyuan Shanxi 030031 P. R. China
2. FIT Freiburg Centre for Interactive Materials and Bioinspired Technologies University of Freiburg 79110 Freiburg Germany
3. Cluster of Excellence livMatS @ FIT 79110 Freiburg Germany
4. Fraunhofer IWM, MikroTribologie Centrum μTC 79108 Freiburg Germany
5. College of Chemistry Taiyuan University of Technology Taiyuan Shanxi 030024 P. R. China