Chemical synthesis, structural elucidation and quantum-chemical modeling of a doped gallium oxynitride prepared by precursor nitridation

Chromium doped gallium oxynitrides having the wurtzite structure were prepared by ammonia nitridation of oxide precursors derived via the citrate route. The solid solution limits of less than 1 at.% Cr3+ were confirmed by both XRD and EXAFS on the nitrided product at 750 ∘C in the wurtzite-type crystal lattice. The doped product was paramagnetic with a small amount of an antiferromagnetic impurity, but there was no ferromagnetic interaction among the doped Cr3+ ions in the gallium oxynitride. Density-functional electronic structure calculations on the basis of a wurtzite-type supercell containing 194 atoms reveal the oxynitride material to be metastable, and confirm the presence of spin-polarized Cr3+ cations located exactly on former Ga3+ tetrahedral sites.