Role of vacancy-type defects in magnetism of GaMnN

Role of vacancy-type (N vacancy (V_N) and Ga vacancy (V_Ga)) defects in magnetism of GaMnN is investigated by first-principle calculation. Theoretical results show that both the V_N and V_Ga influence the ferromagnetic state of a system. The V_N can induce antiferromagnetic state and the V_Ga 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 V_N 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.