  We investigate magnetization reversal of two-body uniaxial Stoner particles,
by injecting spin-polarized current through a spin-valve structure. The
two-body Stoner particles perform synchronized dynamics and can act as an
information bit in computer technology. In the presence of magnetic
dipole-dipole interaction (DDI) between the two particles, the critical
switching current $I_c$ for reversing the two dipoles is analytically obtained
and numerically verified in two typical geometric configurations. $I_c$
bifurcates at a critical DDI strength, where $I_c$ can be decreased to about
70% of the usual value without DDI. Moreover, we also numerically investigate
the magnetic hysteresis loop, magnetization self-precession, reversal time and
the synchronization stability phase diagram for the two-body system in the
synchronized dynamics regime.
