Half-metallicity in two-dimensional Co₂Se₃ monolayer with superior mechanical flexibility

Pursuing two-dimensional (2D) intrinsic ferromagnetism with high Curie temperature and great mechanical flexibility has attracted great interest in flexible spintronics. In the present work, we carried out a density functional theory (DFT) investigation on the 2D M₂Se₃ (M = Co, Ni, and Pd) monolayers to understand their structural stabilities, electronic, magnetic and mechanical properties. Our results show that the Co₂Se₃ monolayer exhibits a fascinating half-metallic ferromagnetism with high Curie temperature (~600 K). In addition, due to their unique buckling hinge-like structure, M₂Se₃ monolayers possess the large out-of-plane negative Poisson's ratio (NPR) and superior mechanical flexibility evidenced by their unusual critical strain (~50%-60%) two times greater than the well-known 2D materials. These findings imply that 2D M₂Se₃ family is the promising materials for the applications in the flexible and high-density spintronic nanodevices.