Ferromagnetism in p-Type Manganese-Doped Zinc Oxide Quantum Dots.

The magnetic exchange interactions between paramagnetic Mn(2+) dopants in the presence of a N(2-) p-type defect in zinc oxide quantum dots are studied using density functional theory. Spin-dependent delocalization of the N(2-) 2p acceptor level among the nearest-neighbor Mn(2+) dopants is observed. The calculations show that parallel Mn(2+) spin alignment is favored upon the formation of a nitrogen-bridged Mn-Mn dimer.