First-principles study on the electronic structures and ferromagnetism of tetragonal AlN monolayer doped with Be and C

The electronic and magnetic properties of Be- and C-doped t-AlN monolayers are studied using spin-polarized density functional calculations. The results show that the Be- and C-doped t-AlN monolayers have magnetic semiconductor feature, and the generated magnetic moments are free of d electrons. Both of the Be- and C-doped t-AlN monolayers show the traits of ferromagnetic (FM) state. Especially for the Be-doped system, it can exhibit robust long-distance magnetic coupling. Finally, under the biaxial strains from -6% to +6%, they still possess the magnetic semiconductor feature, except that the Be-doped t-AlN monolayer becomes half-metallic characteristic by applying -4% compressive strain.