Pure Spin Currents In Silicon Generated, Modulated, And Electrically Detected

Scientists at the Naval Research Laboratory (NRL) have generated, modulated and electrically detected a pure spin current in silicon, the semiconductor used most widely in the electronic device industry. Magnetic contacts on the surface of an n-type silicon layer enable generation of a spin current which flows separately from a charge current. The spin orientation is electrically detected as a voltage at a second magnetic contact. The relative magnetizations of these contacts allow full control over the orientation of the spin in the silicon channel. This was accomplished in a lateral transport geometry using lithographic techniques compatible with existing device geometries and fabrication methods.

In this very recent work, NRL scientists first inject a spin polarized electrical current from a ferromagnetic iron / aluminum oxide tunnel barrier contact into silicon, which generates a pure spin current flowing in the opposite direction (see figure). This spin current produces shifts in the spin-dependent electrochemical potential, which can be electrically detected outside of the charge path at a second magnetic contact as a voltage.

The NRL team showed that this voltage is sensitive to the relative orientation of the spin in the silicon and the magnetization of the detecting contact . They further showed that the orientation of the spin in the silicon could be uniformly rotated by an applied magnetic field, a process referred to as coherent precession, demonstrating that information could be successfully imprinted into the spin system and read out as a voltage. The generation of spin currents, coherent spin precession and electrical detection using magnetic tunnel barrier contacts and a simple lateral device geometry compatible with "back-end" silicon processing will greatly facilitate development of silicon-based spintronic devices.

Posted: Dec 04,2007 by Ron Mertens