**Author details**

Vladimir Koval1\*, Giuseppe Viola2,3 and Yongqiang Tan4

\*Address all correspondence to: vkoval@imr.saske.sk

1 Institute of Materials Research, Slovak Academy of Sciences, Kosice, Slovakia

2 Department of Applied Science and Technology, Institute of Materials Physics and Engi‐ neering, Torino, Italy

3 School of Engineering and Materials Science, Queen Mary University of London, London, UK

4 School of Physics, Shandong University, China
