  Ultrafast photo-induced phase transitions occurring under the impact of
femtosecond laser pulses provide versatile opport unities for switching solids
between distinctly-different crystalline, electronic, and magnetic states and
thus modify their functional properties in a significant way. In this paper, we
report on the laser-induced spin reorientation and Verwey phase transitions in
a single crystalline ferrimagnetic magnetite Fe$_3$O$_4$. Using femtosecond
optical and magneto-optical pump-probe techniques, we define the range of the
initial sample temperatures and laser fluences when partialor complete
photo-induced phase transitions occur from a monoclinic insulating to a cubic
metallic state with concomitant switching of magnetic anisotropy from the
uniaxial to the cubic one. We thus reveal a connection between these phase
transitions when driven by femtosecond laser pulses.Using transient linear and
quadratic magneto-optical effects, we examine magnetization dynamics launched
the switching of the magnetic anisotropy axis. We unveil the presence of the
domains under going the laser-induced phase transitions even below the
established threshold fluence for the transitions, as well as when the material
is initially in the cubic phase. This is the manifestation of the first-order
of these both laser-induced phase transitions beyond the range of thermodynamic
equilibrium.
