Novel magnetic Ni-N-Ni Centers in NiO: A Path to Quantum Sensing

Defect centers, such as nitrogen-vacancy (NV) centers in diamond, have emerged as promising platforms for quantum technologies, including quantum sensing and spin-based qubits. Following the concept of creating individual centers, we investigate local electronic states and magnetic ordering in nickel oxide (NiO) induced by substituting oxygen (O) with nitrogen (N). Each N introduces an additional N 2p hole and alters the state of the magnetic moment at a neighboring nickel (Ni) cation site, as the exchange interaction between this hole and the Ni e_g electrons is larger than the Ni-O-Ni superexchange interaction. This leads to the formation of Ni-N-Ni centers consisting of five spins that are magnetically decoupled from the rest of the antiferromagnetic (AFM) NiO lattice and exhibit degenerate spin states. These centers are studied using density functional theory and confirmed through high-resolution spectroscopy on N-substituted NiO thin films grown by molecular beam epitaxy. This type of magnetic design could potentially advance quantum technologies based on strongly correlated materials, such as quantum sensors and spin-qubits.

Reference: S. Godin, I. S. Elfimov, F. Li, B. A. Davidson, R. Sutarto, J. D. Denlinger, L. H. Tjeng, G. A. Sawatzky, and K. Zou, “Novel magnetic Ni-N-Ni centers in N-substituted NiO”, arxiv.org/abs/2412.19250