  Competition between superconducting and ferromagnetic ordering at interfaces
between ferromagnets (F) and superconductors (S) gives rise to several
proximity effects such as odd-triplet superconductivity and spin-polarized
supercurrents. A prominent example of an S/F proximity effect is the spin
switch effect (SSE) observed in S/F/N/F superconducting spin-valve multilayers,
in which the superconducting transition temperature T$_c$ is controlled by the
angle $\phi$ between the magnetic moments of the F layers separated by a
nonmagnetic metallic spacer N. Here we present an experimental study of SSE in
Nb/Co/Cu/Co/CoO$_x$ nanowires measured as a function of bias current flowing in
the plane of the layers. These measurements reveal an unexpected dependence of
T$_c(\phi)$ on the bias current: T$_c(\pi)$--T$_c(0)$ changes sign with
increasing current bias. We attribute the origin of this bias dependence of the
SSE to a spin Hall current flowing perpendicular to the plane of the
multilayer, which suppresses T$_c$ of the multilayer. The bias dependence of
SSE can be important for hybrid F/S devices such as those used in cryogenic
memory for superconducting computers as device dimensions are scaled down to
the nanometer length scale.
