Grain boundary-driven magnetism in aluminum nitride

Introducing magnetism into III-nitrides to achieve diluted magnetic semiconductors (DMSs) is promising to broaden the applications of III-nitrides. The most popular technique is doping transition metals; however, these structural imperfections are unstable due to significant lattice incompatibility with the host. As a result, the fabrication of high-quality samples is quite difficult through the current growth techniques. Therefore, realizing intrinsic and robust magnetism in III-nitrides is quite desirable. Here, we adapted aluminum nitride as the example to theoretically predict the stable magnetism driven by the ubiquitous grain boundaries (GBs). The magnetism strongly depends on GBs tilt angles. These GBs cores contain homo-elemental bonds antiferromagnetically coupled at high tilt angles (>16.7°) due to the short coupling distances. The Tc was as high as 293 K at the tilt angle of 32.2°. Importantly, the magnetism induced by GBs is robust regarding carrier doping and strain, implying stable magnetism under working conditions. Our results provided a feasible and flexible approach to convert III-nitride into a wide-gap DMS by engineering the topological GBs.