The observed ferromagnetism in Gd-doped GaN appeared to arise from lattice

defects incorporated along with Gd rather than from Gd itself. A previous model,

invoking Ga vacancies as the primary defect responsible for the magnetism was

here argued to be unlikely because Ga vacancies have a high energy of formation

in the neutral charge state that carries magnetic moment. Interstitial nitrogen as well as oxygen in octahedral sites next to Gd were shown to be a more likely

source of defect induced magnetism. They not only support magnetic moments and

ferromagnetic coupling in semi-insulating conditions but were also energetically

attracted toward the Gd and energetically more likely to form in the presence of

Gd.

Interstitial-Nitrogen- and Oxygen-Induced Magnetism in Gd-Doped. C.Mitra,

W.R.L.Lambrecht: Physical Review B, 2009, 80[8], 081202