Realization of high Curie temperature ferromagnetism in atomically thin MoS2 and WS2 nanosheets with uniform and flower-like morphology

Abstract

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.