The theory of light-induced formation of spin autowaves in weak ferrom
agnets, such as FeBO3, caused by special non-equilibrium photo-induced
magnetic anisotropy is constructed. The description is based on the c
oupled set of phenomenological equations for the iron sublattice magne
tizations and for the parameters describing the induced anisotropy. Th
e theoretical results are in good agreement with the experimental data
. Some bifurcations of the solution appear with the changing of the pa
rameters of the magnet.