  Through time-resolved two-color magneto-optical Kerr spectroscopy we have
demonstrated that photogenerated transient carriers decrease the coercivity of
ferromagnetic InMnAs at low temperatures. This transient ``softening'' persists
only during the carrier lifetime ($\sim$ 2 ps) and returns to its original
value as soon as the carriers recombine to disappear. We discuss the origin of
this unusual phenomenon in terms of carrier-enhanced ferromagnetic exchange
interactions between Mn ions and propose an entirely nonthermal scheme for
magnetization reversal.
