Magnetic Properties of Graphene Quantum Dots Embedded in h-BN Sheet

We investigate the energetics and magnetic properties of two graphene dots with triangular shapes embedded in an h-BN sheet. Our first-principles total-energy calculations show that the graphene dots in h-BN prefer the closest interdot spacing as their ground state arrangement. Furthermore, total energy of the heterosheet monotonically increases with increasing interdot spacing and immediately becomes saturated at 0.21 and 0.12 eV for NC and BC borders, respectively, at the interdot spacing of 7.5 Å. We also find that ferrimagnetic spin polarization occurs on each graphene dot with S = 1 / 2 magnetic moment, which are aligned in singlet and triplet arrangement between two dots under interdot spacings of 5.0 Å or larger. The spin polarization energy becomes saturated at approximately 100 meV per graphene dot at an interdot spacing of 8.0 Å. The spin–spin interaction J prefers an antiparallel spin coupling to a parallel one with an energy of 25 meV at an interdot spacing of 5.0 Å.