Observation of nonreciprocal magnetophonon effect in nonencapsulated few-layered CrI(3)

“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 magnetophonon Raman scattering effect in ferromagnetic few-layer CrI(3). We observed a rotation of the polarization plane of inelastically scattered light between −20(o) and +60(o) 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 two-dimensional ferromagnetic materials in Raman lasing, topological photonics, and magneto-optical modulator for information transport and storage.