The problem of spin current across a ferromagnetic/normal metal/ferromagnetic junction is formulated. It
is shown that the spin current is controlled by the phase difference across the junction. Under zero bias, J Szz is time-independent and J Sx (Sy )z is sinusoidal function, where J Szz is the Sz current along z-direction.
Under a dc bias, J Szz and J Sxz + iJSy
z are sinusoidal and the phase of the latter is in front by ÃÂ.