Role of vacancy-type defects in magnetism of GaMnN**Project supported by the National Natural Science Foundation of China (Grant Nos. 61204008, 11075176, and 11505211) and the National Key Basic Research Special Foundation of China (Grant No. 2013CB328705).

Abstract

Role of vacancy-type (N vacancy (VN) and Ga vacancy (VGa)) defects in magnetism of GaMnN is investigated by first-principle calculation. Theoretical results show that both the VN and VGa influence the ferromagnetic state of a system. The VN can induce antiferromagnetic state and the VGa indirectly modify the stability of the ferromagnetic state by depopulating the Mn levels in GaMnN. The transfer of electrons between the vacancy defects and Mn ions results in converting Mn3+ (d4) into Mn2+ (d5). The introduced VN and the ferromagnetism become stronger and then gradually weaker with Mn concentration increasing, as well as the coexistence of Mn3+ (d4) and Mn2+ (d5) are found in GaMnN films grown by metal–organic chemical vapor deposition. The analysis suggests that a big proportion of Mn3+ changing into Mn2+ will reduce the exchange interaction and magnetic correlation of Mn atoms and lead to the reduction of ferromagnetism of material.