High Curie temperature ferromagnetism has been realized in atomically thin MoS2 and WS2 nanosheets. The ultrathin nanosheet samples were prepared via a novel, simple and efficient chemical vapor deposition method; different kinds of transition metal disulfides (MoS2 and WS2) could be obtained by sulphuring the corresponding cation sources (MoO3 and WCl6). Through related morphological and structural characterization, we confirm that large-area, uniform, few-layer MoS2 and WS2 nanosheets were successfully synthesized by this method. Both nanosheet samples exhibit distinct ferromagnetic behavior. By careful measurement and fitting of the magnetization of MoS2 and WS2 samples at different temperatures, we deconstruct the magnetization into its diamagnetic, paramagnetic and ferromagnetic contributions. The ferromagnetic contributions persist until 865 K for MoS2 and 820 K for WS2. We attribute the observed ferromagnetic properties to the defects and dislocations produced during the growth process, as well as the presence of edge spins at the edge of the nanosheets.
Two-dimensional ferromagnetic ultrathin nanosheets hold great promise for next generation electronics and spintronics. Here, intrinsic ferromagnetism was achieved through a new effective strategy by fluorine adsorption on MoS2 nanosheets, where the fluorinated MoS2 nanosheets exhibit stable ferromagnetic hysteresis at room temperature with saturation magnetization of 0.06 emu g(-1) and magnetoresistance of 4.1%. The observed ferromagnetism can be tuned by changing the concentration of the adatom. On the basis of first-principle calculations, it is shown that not only fluorine absorbed MoS2 monolayer favours spontaneous spin polarization and local moment formation, but also that the spin moments can exhibit long range magnetic ordering. This work paves a new pathway to engineer the magnetic properties of the two-dimensional nano-materials.
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