  To conduct spin-sensitive transport measurements, a non-local device geometry
is often used to avoid spurious voltages that are caused by the flow of
charges. However, in the vast majority of reported non-local spin valve, Hanle
spin precession, or spin Hall measurements background signals have been
observed that are not related to spins. We discuss seven different types of
these charge-induced signals and explain how these artifacts can result in
erroneous or misleading conclusions when falsely attributed to spin transport.
The charge-driven signals can be divided into two groups: Signals that are
inherent to the device structure and/or the measurement setup and signals that
depend on a common-mode voltage. We designed and built a voltage-controlled
current source that significantly diminishes all spurious voltage signals of
the latter group in both DC and AC measurements by creating a virtual ground
within the non-local detection circuit. This is especially important for
lock-in-based measurement techniques, where a common-mode voltage can create a
phase-shifted, frequency-dependent signal with an amplitude several orders of
magnitude larger than the actual spin signal. Measurements performed on
graphene-based non-local spin valve devices demonstrate how all spurious
voltage signals that are caused by a common-mode voltage can be completely
suppressed by such a current source.
