  Monolayer NaCrX2 (X=Te,Se,S) were theoretically proposed to be
two-dimensional intrinsic ferromagnetic semiconductors while their physical
properties have not been thoroughly investigated in bulk single crystals. We
report the single-crystal growth, structural, magnetic and electronic transport
properties of NaCr(Te1-xSex)2 (0 6 x 6 1) and NaCrS2. For NaCr(Te1-xSex)2, the
strong perpendicular magnetic anisotropy of NaCrTe2 can be gradually tuned to
be a nearly isotropic one by Se-doping. Meanwhile, a systematic change in the
conductivity with increasing x is observed, displaying a doping-induced
metal-insulator-like transition. Under magnetic field larger than 30 koe, both
NaCrTe2 and NaCrSe2 can be polarized to a ferromagnetic state. While for
NaCrS2, robust antiferromagnetism is observed up to 70 kOe and two
field-induced metamagnetic transitions are identified along H||ab. These
intriguing properties together with the potential to be exfoliated down to
few-layer thickness make NaCrX2 (X=Te,Se,S) promising for exploring spintronic
applications.
