  Two-dimensional (2D) Janus semiconductors with mirror asymmetry can introduce
novel properties, such as large spin-orbit coupling (SOC) and normal
piezoelectric polarization, which have attracted a great interest for their
potential applications. Inspired by the recently fabricated 2D ferromagnetic
(FM) semiconductor CrI3, a stable 2D (in x-y plane) antiferromagnetic (AFM)
Janus semiconductor Fe2Cl3I3 with normal sublattice magnetization (m//z) is
obtained by density functional theory calculations. By applying a tensile
strain, the four magnetic states sequentially occur: AFM with m//z of
sublattice, AFM with m//xy of sublattice, FM with m//xy, and FM with m//z. Such
novel magnetic phase diagram driven by strain can be well understood by the
spin-spin interactions including the third nearest-neighbor hoppings with the
single-ion anisotropy, in which the SOC of I atoms is found to play an
essential role. In addition, the electric polarization of Fe2Cl3I3 preserves
with strain due to the broken inversion symmetry. Our results predict the rare
Janus material Fe2Cl3I3 as an example of 2D semiconductors with both spin and
charge polarizations, and reveal the highly sensitive strain-controlled
magnetic states and magnetization direction, which highlights the 2D magnetic
Janus semiconductor as a new platform to design spintronic materials.
