Probing Spin Flip Scattering in Ballistic Nanosystems
Z. M. Zeng, J. F. Feng, Y. Wang (all at Chinese Acad of Sci) X. F.
Han (Chinese Acad of Sci, now CNMS User),
W. S. Zhan (Chinese Acad
of Sci) X.-G. Zhang (CNMS staff) and
Z. Zhang (Bejing Univ of Tech)
Using data provided by colleagues at the Institute of Physics, Chinese
Academy of Science, we have demonstrated a way to measure the electron
spin-flip length in nanoscale materials. We showed that the measurement
could be made by comparing the magnetoresistance of electrons traveling
through single and double layer arrangements of an insulating material
(barrier layers) made of the same materials and connected to the same
type of magnetic electrodes. The voltage and temperature dependences
of the spin-flip conductance in the spacer layer are extracted from
the magnetoresistance measurements. In addition to the spin scattering
information including the electron mean-free-path of 70 nm and the
spin-flip scattering length of 1-2.6 microns at 4.2K, this technique
also yields information on the density of states and quantum well resonance
in the spacer layer. The quantum well resonance is shown to greatly
enhance the spin-flip scattering. The linear temperature dependence
of the spin flip scattering strength in copper suggests a phononic
original of such scattering.
One of the challenges in the physics of spintronics is the study of
spin-flip scattering and its effect on magnetotransport. Spin-flip
scattering in nonmagnetic metals has been studies in the past by connecting
a metal wire hundreds of nanometers in length to multiple magnetic
electrodes. Such measurements are difficult in nanoscale devices because
electrons' spins in a nonmagnetic material rarely flip until they travel
a distance many times the size of the device itself. This means that
possibly just a small fraction of electrons would flip inside a nanoscale
device, an attribute that may make electrons' magnetic properties attractive
for storage, sensors and, potentially, quantum computing.
demonstrates for the first time that the spin-flip scattering can
be measured in nanoscale systems, even when the spin-flip length
is thousands of times greater than the physical size of the system.
The ability to determine the precise spin-flip lengths for each device
will allow scientists to better exploit those properties to create
spintronics-based electronics of the future.
of this work is published as Phys. Rev.Lett. 97, 106605 (2006).
Z. M. Zeng1, J. F. Feng1, Y. Wang1, X. F. Han1, W. S. Zhan1, X.-G.
Zhang2, and Z. Zhang3, of 1Institute of Physics, Chinese Academy
of Science, 2Center for Nanophase Materials Sciences, Oak Ridge
National Laboratory, and 3Beijing University of Technology.