experimentally. [9][10][11][12][13][14] In addition, graphene allows the FR angles being controlled continuously by external parameters such as chemical potential or an external magnetic field, which is superior to that of conventional bulky magnetic materials always with fixed MO properties. Therefore, graphene opens up great possibilities for MO functionalities, such as optical isolators and one-way transmission devices based on 2D layered materials. [15,16] The successful exfoliation of monolayer transitional metal dichalcogenides (TMDC) inspires a broad exploration of optical and MO properties in related materials. [17][18][19][20][21][22][23][24][25][26][27][28][29][30] Monolayer TMDC family can be represented as the type of MX 2 (M = Mo, W, V and X = S, Se, or Te), in which M atoms are sandwiched between two planes of X atoms. The coexistence of broken inversion symmetry and strong spin-orbit coupling (SOC) of monolayer MX 2 makes them promising platforms for various valley-related properties, such as valley Hall effects as well as valley polarization. [18,20,21] It was known that the electronic structures of monolayer MoS 2 are protected by time reversal symmetry and thus there are no intrinsic magneto-optical effects in its pristine form. A key requirement for the generation of MO effects is to break time reversal symmetry, thus it is a promising way to apply an external magnetic field upon the system. [25][26][27][28] In this regard, there have been significant advancements in the MO effects of monolayer MX 2 . It has been reported that valley Zeeman splitting, polarization, and coherence of the excitonic valley pseudospin can be controlled by virtue of magnetic field, which have been observed in monolayer WSe 2 by performing polarization-resolved magnetophotoluminescence. [25] The possibility of producing a rotation of the emission polarization with respect to the excitation (the coherent superposition of valley states) has been confirmed in monolayer WS 2 (WSe 2 ), whose rotation angle can be up to 35° (30°) when the applied magnetic field reaches up to be 25 T (9 T). [29,30] These works establish the key steps toward understanding the intrinsic spin and valley properties of monolayer MX 2 .However, the above MO-related behaviors in monolayer MX 2 always require strong magnetic fields, severely restricting their realistic applications. The generation of MO effects in monolayer MX 2 will be particularly interesting if there is no need of magnetic field, as that would allow 2D layered materials in more practical positions for the realization of MO devices.Monolayer transition metal dichalcogenides represent a class of 2D directbandgap semiconductors, which do not support magneto-optical (MO) effects in the absence of magnetic field due to time reversal symmetry. Magnetic exchange field (MEF) has been demonstrated to be able to generate MO effects in monolayer transition metal dichalcogenides, causing Faraday rotation of several tenths of degree without the need of magnetic field. Here, the possibility of...