Mott transition and superexchange mechanism in magnetically doped XSi2 N4 caused by large 3d orbital onsite Coulomb interaction

Magnetic two-dimensional materials have great potential in the preparation of nanoelectronic and spintronic devices. Recently, a new two-dimensional material with no corresponding bulk-structure, MoSi2N4, has been prepared, attracting public attention to the XA2Z4 series of materials. Naturally, doping with 3d magnetic element will result in various magnetic orderings. In our work, we replaced the Mo element with different transition-metal elements whose property varies from magnetic to nonmagnetic and screened out a variety of two-dimensional exchange scenarios. Then, we provided an analysis that shows the existence of a huge on-site Coulomb interaction at 3d orbitals which is strongly related to the Mott transition and therefore causes the superexchange interaction.