Electronic and magnetic properties of manganese and iron-doped GanAsn nanocages (n=7-12)

The electronic and magnetic properties of Mn- or Fe-doped GanAsn (n=7-12) nanocages were studied using gradient-corrected density-functional theory considering doping at substitutional, endohedral, and exohedral sites. When doped with one atom, the most energetically favorable site gradually moves from surface (n=7-11) to interior (n=12) sites for the Mn atom, while the most preferred doping site of the Fe atom alternates between the surface (n=7,9,11) and interior (n=8,10,12) sites. All of the ground-state structures of Mn@GanAsn have the atomlike magnetic moment of 5 mu(B), while the total magnetic moments of the most stable Fe@GanAsn cages for each size are about 2 mu(B) except for the 4 mu(B) magnetic moment of Fe@Ga12As12. Charge transfer and hybridization between the 4s and 3d states of Mn or Fe and the 4s and 4p states of As were found. The antiferromagnetic (AFM) state of Mn-2@GanAsn is more energetically favorable than the ferromagnetic (FM) state. However, for Fe-2@GanAsn the FM state is more stable than the AFM state. The local magnetic moments of Mn and Fe atoms in the GanAsn cages are about 4 mu(B) and 3 mu(B) in the FM and AFM states, respectively. For both Mn and Fe bidoping, the most energetically favorable doping sites of the transition metal atoms are located on the surface of the GanAsn cages. The computed magnetic moments of the doped Fe and Mn atoms agree excellently with the theoretical and experimental values in the Fe(Mn)/GaAs interface as well as (Ga, Mn)As dilute magnetic semiconductors. (c) 2008 American Institute of Physics.