Research Director: Dr. Hideo Ohno
(Professor, Reserch Institute of Electrical Communication, Tohoku University)
Research Term: 2002-2007

The Ohno Semiconductor Spintronics project is aimed at understanding how to utilize the spin degree of freedom in semiconductors while integrating materials and device science and technology.

One of our recent progresses is the observation of pulsed current induced magnetic domain wall motion in the ferromagnetic semiconductor (Ga,Mn)As, with a low current density of the order of 105A/m. We demonstrated the motion to be understood in terms of the spintransfer mechanism. Furthermore, we found that in the subthreshold creep regime, the current and the magnetic field drives belong to different universality classes.

Secondly, the electrical manipulation of the coercive force and electrically assisted magnetization reversal were demonstrated by modifying the carrier density through the application of an electric field in both (In,Mn)As and (Ga,Mn)As FET. This electrical manipulation may become useful for reversing the magnetization of nanoscale bits in ultrahigh density information storage.

Thirdly, the local manipulation and detection of the nuclear spin coherence in GaAs/AlGaAs quantum wells were demonstrated by an optical pump-probe technique combined with pulse rf NMR. By time-resolved Kerr rotation with pulsed rf magnetic fields, the Rabi oscillations of the nuclear spins as well as quantum gate actions were traced, while the intrinsic coherence time was evaluated by a spin-echo technique. These open a door for future semiconductor quantum information technologies using nuclear spins.