High throughput discovery of 2D ferromagnetic and multiferroic transition metal oxyhalides and nitrogen halides

Two-dimensional (2D) transition metal oxyhalides and nitrogen-halides ( T M BXs , where T M = transition metal, B = O-group and N-group elements, X = halogen) have emerged as promising candidates for exploring multiferroic orders and spintronic applications. In this study, we conduct a systematic first-principles high-throughput screening combined with machine learning to identify novel 2D ferromagnetic and multiferroic materials within T M BX family. From a comprehensive dataset comprising 672 T M BX monolayers, we identify 78 ferromagnetic systems, of which 38 exhibit high Curie temperatures ( T C ≥ 200 K), significantly expanding the known library of 2D magnetic materials. A machine learning model is developed to elucidate the key factors governing ferromagnetism, revealing that the second-nearest neighbor exchange interaction ( J 2 ) plays a dominant role in determining T C . Furthermore, we discovered seven ferromagnetic-ferroelectric multiferroic systems, revealing unique polarization switching pathways. Notably, spin transport simulations using the nonequilibrium Green’s function formalism demonstrate exceptional spin filtering capabilities (~100%) and giant bias-dependent tunneling magnetoresistance (>10 5 %). These findings deepen the fundamental understanding of 2D multiferroics and establish a desired platform for future experimental exploration and the development of next-generation spintronic devices.