  We use a non-equilibrium many-body theory that engages the elements of
transient coherence, correlation, and nonlinearity to describe changes in the
magnetic and electronic phases of strongly correlated systems induced by
femtosecond nonlinear photoexcitation. Using a generalized tight--binding mean
field approach based on Hubbard operators and including the coupling of the
laser field, we describe a mechanism for simultaneous insulator--to--metal and
anti-- to ferro--magnetic transition to a transient state triggered by
non-thermal ultrafast spin and charge coupled excitations. We demontrate, in
particular, that photoexcitation of composite fermion quasiparticles induces
quasi-instantaneous spin canting that quenches the energy gap of the
antiferromagnetic insulator and acts as a nonadiabatic "initial condition" that
triggers non-thermal lattice dynamics leading to an insulator to metal and
antiferromagnetic (AFM) to ferromagnetic (FM) transitions. Our theoretical
predictions are consistent with recent ultrafast pump-probe spectroscopy
experiments that revealed a magnetic phase transition during 100fs laser pulse
photoexcitation of the CE--type AFM insulating phase of colossal
magnetoresistive manganites. In particular, experiment observes two distinct
charge relaxation components, fs and ps, with nonlinear threshold dependence at
a pump fluence threshold that coincides with that for femtosecond magnetization
photo excitation. Our theory attributes the correlation between femtosecond
spin and charge nonlinearity leading to transition in the magnetic and
electronic state to spin/charge/lattice coupling and laser-induced quantum spin
canting that accompanies the driven population inversion between two
quasi--particle bands with different properties: a mostly occupied polaronic
band and a mostly empty metallic band, whose dispersion is determined by
quantum spin canting.
