Magnetic skyrmion, as a topologically protected whirl-like soliton, has been subjecting to growing interest in non-volatile spintronic memories and logic devices. More recently, much effort has been devoted to searching for skyrmion host materials in two-dimension (2D) systems, where intrinsic inversion symmetry breaking and large Dzyaloshinskii-Moriya interaction (DMI) are most desirable to realize the field-free skyrmion state. Among these, 2D magnetic Janus materials become important candidates for inducing sizable DMI and chiral spin textures. Herein, we demonstrate that layer-dependent DMI and field-free magnetic skyrmion can exist in multilayer MnSTe. Moreover, the strong interlayer exchange coupling existing Bethe-Slater-curve-like behaviors and arising from the Mn-Mn double exchange mechanism is illustrated in bilayer MnSTe. Concurrently, we uncover that the distributions of DMIs in multilayer MnSTe can be understood as the significant contribution of intermediate part DMI via using the three-site Fert-Lévy model. Our results unveil the great potential for designing skyrmion-based spintronic devices in multilayer 2D materials.

Based on the first-principles calculations, we examine the effect of hole doping on the ferromagnetism and Dzyaloshinskii-Moriya interaction (DMI) for PbSnO2, SnO2 and GeO2 monolayers. The nonmagnetic to ferromagnetic transition and the Dzyaloshinskii-Moriya interaction can emerge simultaneously in the three two-dimensional (2D) IVA oxides. By increasing the hole doping concentration, we find the ferromagnetism can be strengthened for the three oxides. Due to different inversion symmetry breaking (ISB), isotropic DMI is found in PbSnO2，whereas anisotropic DMI presents in SnO2 and GeO2. More appealingly, for PbSnO2 with different hole concentrations, DMI can induce a variety of topological spin textures. Interestingly, a peculiar feature of synchronously switch of magnetic easy axis and DMI chirality upon hole doping is found in PbSnO2. Hence, topological magnetism can be tailored via changing hole density in PbSnO2. Our findings demonstrate the presence and tunability of topological chiral structures in p-type magnets and open up new possibility for spintronics.