We reported optical, defect levels and spin coherence properties of Ni-Mg center in MgO, which consists of a substitutional nickel atom in a magnesium site. Our study is based on the first-principles calculation and experimental analysis. The neutral of Ni-Mg center is stable in the p-type MgO. The defect center possesses a triplet ground state and is optically accessible. According to a mean-field-based scheme, the spin coherence time of neutral Ni-Mg center is estimated to be 0.33 s at T = 0 K. Moreover, it is confirmed that ion implantation at room temperature can be an efficient way to produce the neutral Ni-Mg centers in MgO.
