Takuto Tsukahara, Satoshi An, Sho Otsuru, Yasuhisa Tezuka2, Shunsuke Nozawa, Junichi Adachi, Kenta Akashi, Yuji Inagaki, Tatsuya Kawae, Hirofumi Ishii, Yen-Fa Liao, Tetsuya Kida, Satoshi Suehiro, Masashi Nantoh, Koji Ishibashi and Yoichi Ishiwata
We systematically investigate the unoccupied electronic states, crystal structure, and magnetism of V- and Mn-doped ZnO nanocrystals (NCs). Post-annealing treatment at 300 C converts diamagnetic V5þ into magnetic high-spin V3þ ions, which leads to room-temperature ferromagnetism for the V-doped NCs. In contrast, ferromagnetism does not occur for the Mn-doped NCs. Oxygen 1s x-ray absorption spectroscopy reveals that the unoccupied metal-oxygen hybridized state lies near the bottom of the conduction band for the V-doped NCs but lies far above it for the Mn-doped NCs. Therefore, the ferromagnetism in a ZnO-based diluted magnetic semiconductor system can be understood within the framework of the n-type carrier-mediated ferromagnetism model.
Research papers (academic journals)
