千葉 大地


千葉 大地

Winner in 2012 | 14th Winner

Associate Professor, Institute for Chemical Research, Kyoto University


Electric field-induced ferromagnetic phase transition in semiconductors and metals


Abstract When Prize Awarded

Electrical control of magnetism adds a new dimension to future spin-based information processing methods. Use of an electric field instead of an electric current is expected to make ultra-low power driving devices possible. Ferromagnetic semiconductors had been the central material for this kind of research because their magnetic properties are a function of the carrier concentration.

We have reported, for the first time, on the electric field control of the ferromagnetic phase transition and tuning of the Curie temperature using (In, Mn) As in 2000, a ferromagnetic semiconductor [1]. We also reported, in 2003, an electric field-induced coercivity change, and an electric-field assisted magnetization switching was demonstrated by using it [2]. We also demonstrated, in 2008, that the magnetization direction can be manipulated by electrically controlling the magnetic anisotropy of (Ga, Mn) As [3]. These efforts open up an entirely new route for electrical magnetization switching without using a magnetic field or current. Although one of the problems had been a low Curie temperature of the ferromagnetic semiconductors, after our findings the electric field-induced change in magnetic properties using ferromagnetic ultra-thin metals even at room temperature has been reported [4-9]. Using ferromagnetic ultra-thin metallic cobalt, we realized the electric field-induced ferromagnetic phase transition around room temperature [7,8].

I will show the experimental results of electric field

control of various ferromagnetic properties in field effect structures with a channel made of III-V ferromagnetic semiconductors or 3d ferromagnetic transition metals.

I would like to thank H. Ohno, T. Ono, T. Dietl, F. Matsukura, K. Kobayashi, S. Ono, and members of Ohno and Ono labs for their help.

[1]    H. Ohno and D. Chiba et al., Nature 408, 944 (2000).
[2]    D. Chiba, M. Yamanouchi, F. Matsukura, and H. Ohno, Science 301, 943 (2003).
[3]       D Chiba et al., Nature 455, 515 (2008).
[4]       M. Weisheit at al., Science 315, 349 (2007).
[5]       T. Maruyama et al., Nature Nanotechnol. 4, 158 (2009).
[6]       M. Endo et al., Appl. Phys. Lett. 96, 212503 (2010).
[7]       D. Chiba et al., Nature Mater. 10, 853 (2011).
[8]       K. Shimamura and D. Chiba et al., Appl. Phys. Lett. 100, 122402 (2012).
[9]       D. Chiba et al., Nature Comm. 3, 888 (2012).