Direct Exchange in Ultra‐Thin Ferromagnetic Janus MXenes

The development of spintronic devices urgently requires ultra‐thin two‐dimensional (2D) ferromagnetic materials with high Curie temperature (Tc), TC however, there are few natural intrinsic ferromagnetic 2D materials. The successful synthesis of Janus monolayer MoSSe in experiments provides a new approach for designing new 2D materials. By replacing transition metal carbides with two different transition metal atoms, we have designed over 70 Janus MXence materials and determined that 30+ materials have ferromagnetic ground states, of which three have robust ferromagnetism through density functional theory analysis. The ferromagnetic coupling in such materials mainly originates from the direct exchange of d‐orbitals between transition metal atoms in different layers. Further, using K‐nearest neighbours (KNN) machine learning (ML) method, six out of the remaining 360 Janus MXence systems were screened for ferromagnetism, with one system exhibiting strong ferromagnetism. This work provides an alternative and convenient method for developing ultra‐thin 2D magnetic materials for next generation spintronic device applications. The first principles calculations are combined with machine learning (ML) and 30+ ferromagnetic materials are discovered among 400+ double transition metal Janus MXenes materials. The Curie temperature of CrWC and TiNiC exceeds the room temperature. The ferromagnetism in these materials mainly comes from direct exchange between the d‐orbitals of different transition metal atoms.