Electrical manipulation of domain walls and magnetization in ferromagnetic semiconductor structures

Hideo Ohno ^{1, 2}
1 Laboratory for Nanoelectronics and Spintronics, Research Institute of Electrical Communication, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan
2 ERATO Semiconductor Spintronics Project, JST, Japan Phone/Fax: +81-22-217-5553, E-mail: ohno@riec.tohoku.ac.jp

Ferromagnetic III-V semiconductor (Ga,Mn)As is characterized by p-d exchange stabilized ferromagnetism, small magnetization, and strong spin-orbit interaction [1, 2], thus offering a unique combination of physical parameters related to current-induced magnetization reversal. Here we present our study on (1) current driven magnetic domain wall motion in a lithographically defined (Ga,Mn)As structure [3], and (2) current driven magnetization reversal in fully epitaxial (Ga,Mn)As magnetic tunnel junctions (MTJ's) using GaAs as a barrier [4]. In the former, two regimes are found to be present in the domain wall velocity - current density characteristics, showing the importance of spin-polarized current in assisting thermal motion of domain walls. The estimated spin-transfer efficiency is as high as 10% or even higher. In the latter, current density required for the reversal in MTJ is found to be lower than that expected from scaling of magnetization. This work was done in collaboration with D. Chiba, M. Yamanouchi, Y. Sato, T. Kita, and F. Matsukura. This work was supported in part by the IT-Program of RR2002 from MEXT. [1] H. Ohno, Science, 281, 951 (1998). [2] T. Dietl et al., Science, 287, 1019 (2000). [3] M. Yamanouchi et al., Nature, 428, 539 (2004). [4] D. Chiba et al., Phys. Rev. Lett., 93, 216602 (2004).