  Recent experimental work on Au thin films demonstrated signs of charge
current-induced spin polarization through open circuit voltage measurements. In
this study, we are investigating the underlying mechanism(s) that induces this
measured signal in the Au devices. We determine the theoretically expected spin
polarization from both Rashba-Edelstein effect and bulk spin Hall effect. The
discrepancy in the scaling of the measured signal as a function of the
thickness of the Au thin film in the two cases is our key to differentiate
between the two effects when compared to experimental data. Experiments show
reversal of spin polarization at a critical thickness which reveals the
presence of multiple spin polarization mechanisms. Characteristics of both
RashbaEdelstein and spin Hall effects are observed in different thickness
regimes. In addition, we study the magnetoresistance of the same Au samples,
which reveal the presence of weak anti-localization (WAL) at low temperatures
for the low-thickness samples. More interestingly, it is revealed that the open
circuit voltage difference and magnetoresistance due to WAL have very similar
scaling with film thickness and temperature, suggesting the crucial importance
of spin-orbit interaction in understanding the phenomenon.
