Room temperature ferromagnetism in un-doped amorphous HfO2 nano-helix arrays*
Xie Qian, Wang Wei-Peng, Xie Zheng, Zhan Peng, Li Zheng-Cao, Zhang Zheng-Jun†
       
SEM images of nano-arrays from side view and TEM images of single nano-column. (a), (b) Sample with ∞ spirals per column; (c), (d) sample with four spirals per column; (e), (f) sample with two spirals per column; (g), (h) sample with one spiral per column.