Nonlocal
Magnetization Dynamics in Magnetic Heterostructures
Prof John Q Xiao
Department of Physics
and Astronomy
Spin torque transfer refers to a phenomenon that a spin polarized
current can reorient magnetization in multilayer structures. The reorientation
takes place through spin procession caused by the torque from the spin
polarized current. On the equal footing, a processing ferromagnet excited by an
rf external magnetic field
can inject spins into a neighboring layer, termed as spin pumping or spin
battery effect. Such spin pumping can be used to create a pure spin current, which
is heavily investigated and debated in the field of spintronics.
Spin pumping can be indirectly investigated through Gilbert damping
enhancement. More recently, direct electrical measurements has also been
reported in magnetic heterostructures
with ohmic interfaces [1] and tunneling barrier
[2]. While the former have been
well described within the standard spin pumping theory [3], the voltage
generation by magnetization precession of a ferromagnetic layer in tunneling
structures is very intriguing.
Surprising results have also been observed in Gilbert damping
experiment. In this talk, we will
present a systematic experimental investigation of spin pumping effects in
tunneling structures, as well as possible mechanisms.
Ref:
1.
M.
V. Costache, M. Sladkov, S.
M. Watts, C. H. van der Wal,
and B. J. van Wees, Phys. Rev. Lett.
97, 216603 (2006).
2. T. Moriyama, R. Cao, X. Fan, G. Xuan,
B. K. Nikolic, Y. Tserkovnyak, J. Kolodzey, and J. Q. Xiao, Phys. Rev. Lett. 100, 067602 (2008).
3. Y. Tserkovnyak, A. Brataas, G. E. W. Bauer, and B. I. Halperin,
Rev. Mod. Phys. 77, 1375 (2005).