  Lateral spin valves are used to generate and characterize pure spin currents.
Non-local voltage measured in such structures provides information about spin
polarization and spin decay rates. For wide high-transparency F/N contacts it
was shown that the Johnson-Silsbee non-local effect is substantially enriched
by closed-loop electric currents driven by local spin injection in the
electrically dangling part of the valve. For valves with low-transparency F/I/N
tunnel contacts such circular currents are strongly suppressed, yet we show
that the voltage modifications persist, may be significant, and must be
accounted for in the data analysis.
