Influence of oxygen impurities in generating ferromagnetism in GaN doped with Mn, Fe, and Cr

We report the influence of oxygen impurities in generating ferromagnetism in GaN doped with Mn, Fe, and Cr through superexchange involving Mn–O–Mn, Fe–O–Fe, and Cr–N–Cr atomic configurations. Density Functional Theory (DFT) calculations demonstrated that these configurations originate within V_Ga-O_N complex defects by incorporating Mn²⁺, Fe²⁺, and Cr³⁺ ions into gallium vacancies (V_Ga) sites promoted by the presence of oxygen as a substitutional impurity (O_N). These co-doped GaN microstructures were synthesized using the thermal evaporation method. Cathodoluminescence (CL) and photoluminescence (PL) measurements confirmed the presence of V_Ga-O_N complex defects in all GaN-grown samples. X-ray photoelectron spectroscopy (XPS) measurements confirmed the successful incorporation of Mn²⁺, Fe²⁺, and Cr³⁺ ions in GaN samples. SQUID measurements demonstrated room-temperature ferromagnetism with respective saturation magnetization (M_s) and coercive field (H_c) values of ± 1.5 × 10⁻⁵ emu and 4 mT for GaN:O,Mn, ± 4.4 × 10⁻⁵ emu and 2.6 mT for GaN:O,Fe, and ± 1.7 × 10⁻⁵ emu and 2.6 mT for GaN:O,Cr.