University of Minnesota
School of Physics & Astronomy

Academic Calendar

Monday, June 21st 2010
1:30 pm:
Ph. D. Thesis Defense in 435 Physics
Speaker: Eric Garlid, University of Minnesota
Subject: Electrical Detection of the Spin Hall Effect in Ferromagnet-Semiconductor Heterostructures

My thesis investigates the effects of spin-orbit coupling on spin
transport in Ferromagnet/Semiconductor heterostructures. Spin-orbit coupling is a relativistic phenomenon that couples the spin of an electron to its momentum by means of a momentum-dependent effective magnetic field. The effects of spin-orbit coupling in bulk InGaAs are observed by measuring the direct spin Hall effect, where an applied charge current induces a perpendicular spin current. The spins are oriented perpendicular to the flow directions of both the charge current and the spin current.
This spin current leads to an out-of-plane spin accumulation that is
opposite in sign at opposite edges of the channel. The spin accumulation
is identified through the observation of a Hanle effect in the Hall
voltage measured by pairs of ferromagnetic contacts. The data are fit
using a model which includes spin diffusion, precession, and relaxation.
We use the parameters determined from the fit to calculate the spin Hall
conductivity. We find that the magnitude of the spin Hall conductivity is
in agreement with models of the extrinsic SHE due to ionized impurity
scattering. By analyzing the dependence of the spin Hall signal on channel
conductivity we determine the contributions of both skew and side jump
scattering to the total spin Hall conductivity. We calculate that the
spin-orbit coupling parameter is larger than predicted by standard k•p
perturbation theory.

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