  We report experimental study of spin transport in all-metal nanowire spin
valve structures. The nanowires have a diameter of 50 nm and consist of three
layers - cobalt, copper and nickel. Based on the experimental observations, we
conclude that the primary spin relxation mechanism in the paramagnet copper is
the Elliott-Yafet mode associated with frequent interface roughness scattering.
This mode is overwhelmingly dominant over all other modes, so that we are able
to study the pure Elliott-Yafet mode in isolation. We deduce that the effective
spin relaxation length associated with this mechanism is about 16 nm in our
nanowires and is fairly independent of temperature in the range 1 - 100 K. The
corresponding spin relaxation time is about 100 femtoseconds. We also find that
the spin relaxation length or time is fairly independent of the electric field
driving the current in the range 0.75 - 7.5 kV/cm.
