Exploring spin-transfer and spin-Hall effects in mesoscopic metallic structures
University of Delaware
Spintronics relies on the functionalities of spin currents. The
concept of a pure spin current holds a unique place in spintronics.
One can visualize a pure spin current by considering electrons with
opposite spins flow in opposite directions. Pure spin currents are
less invasive and less dissipative compared to spin polarized charge
currents. A pure spin current can be generated by electrical
injection from a ferromagnet in a mesoscopic lateral structure known
as nonlocal spin valve (NLSV). With low-resistance oxide injection
interfaces and high quality nonmagnetic channels, the pure spin
current can be large enough to induce magnetization reversal for a
nanoscale magnet through the spin transfer effects.
A different approach to generate a pure spin current without a
ferromagnet has been recently discovered and known as the spin-Hall
effects. When electron currents flow in a heavy nonmagnetic metal such
as platinum (Pt), the spin-orbit coupling causes electrons with
opposite spins to be scattered into opposite transverse
directions. Therefore a pure spin current is generated in the
direction that is transverse to the electron current. We have
fabricated mesoscopic structures in which a Pt wire is in contact with
a Cu channel and an AlOx barrier is placed in between. The pure spin
current due to the spin-Hall effect in Pt is injected into the Cu
channel across the AlOx barrier. The injected spin accumulation in Cu
is comparable to that from an electric spin injection using a
ferromagnet, demonstrating the effectiveness of spin-Hall effect as a
novel way to generate spin currents.
This work was supported by US DOE grant No. DE-FG02-07ER46374.