Realizing multiferroics in α-Ga ₂ S ₃ via hole doping: a first-principles study

Using first-principles calculations, we report the realization of multiferroics in an intrinsic ferroelectric α-Ga₂S₃ monolayer. Our results show that the presence of intrinsic gallium vacancies, which is the origin of native p-type conductivity, can simultaneously introduce a ferromagnetic ground state and a spontaneous out-of-plane polarization. However, the high switching barrier and thermodynamic irreversibility of the ferroelectric reversal path disable the maintenance of ferroelectricity, suggesting that the defect-free form should be a prerequisite for Ga₂S₃ to be multiferroic. Through applying strain, the behavior of spontaneous polarization of the pristine α-Ga₂S₃ monolayer can be effectively regulated, but the non-magnetic ground state does not change. Strikingly, via an appropriate concentration of hole doping, stable ferromagnetism with a high Curie temperature and robust ferroelectricity can be concurrently introduced in the α-Ga₂S₃ monolayer. Our work provides a feasible method for designing 2D multiferroics with great potential in future device applications.