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)

Scientific Achievement

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.

Significance

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.

Our work 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.

The result of this work is published as Phys. Rev.Lett. 97, 106605 (2006).

Performers:
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.