  Magneto-optical effect refers to a rotation of polarization plane, which has
been widely studied in traditional ferromagnetic metal and insulator films and
scarcely in two-dimensional layered materials. Here we uncover a new
nonreciprocal magneto-inelastic light scattering effect in ferromagnetic
few-layer CrI3. We observed a rotation of the polarization plane of inelastic
light scattering between -20o and +60o that are tunable by an out-of-plane
magnetic field from -2.5 to 2.5 T. It is experimentally observed that the
degree of polarization can be magnetically manipulated between -20% and 85%.
This work raises a new magneto-optical phenomenon and could create
opportunities of applying 2D ferromagnetic materials in Raman lasing,
topological photonics, and magneto-optical modulator for information transport
and storage.
