Magnetism driven by surface dangling bonds in gallium nitride nanoclusters

Magnetic properties of gallium nitride (GaN) semiconductor nanoclusters (NCs) of different sizes were systematically studied by using first-principles calculations. It is observed that the pure GaN NCs can be magnetic even without magnetic elements doping. Similar to the observed magnetism in undoped oxide NCs, the magnetism of the undoped GaN NCs is attributed to the spin polarization of the dangling bond electrons of the 2-coordinate surface nitrogen anions and originates from the spatially localized nature of the dangling bond states and associated on-site Hubbard interaction. It is demonstrated that the magnetism driven by the surface dangling bonds can be suppressed or enhanced via hydrogen passivation or structural design. These results indicate that it is promising to combine the surface magnetism of the GaN NCs with their unique optical properties to fabricate nanosized magneto-optical devices.