  We present a femtosecond optical pump-probe study of the multiferroic
manganite Eu$_{0.75}$Y$_{0.25}$MnO$_3$. The optical response of the material at
pump energies of 1.55 and 3.1 eV is dominated by the $d$-$d$ and $p$-$d$
transitions of the Mn$^{3+}$ ions. The relaxation of photoexcited electrons
includes the relaxation of the Jahn-Teller distortion and polaron trapping at
Mn$^{2+}$ and Mn$^{4+}$ sites. Ultrafast switching of superexchange
interactions due to modulated $e_g$ orbital occupancy creates a localized spin
excitation, which then decays on a time scale of tens of picoseconds at low
temperatures. The localized spin state decay appears as a tremendous increase
in the amplitude of the photoinduced reflectance, due to the strong coupling of
optical transitions to the spin-spin correlations in the crystalline $a$-$b$
plane.
