Optical detection of magnetic resonance of nitrogen and nickel in high-pressure synthetic diamond

Diamonds grown by the temperature-gradient method using a nickel catalyst exhibit a luminescence spectrum that is dominated by a broad band with sharp lines around 2.56 eV. We report optical detection of magnetic resonance of substitutional ${\mathrm{N}}^0$ and substitutional ${\mathrm{Ni}}^{\mathrm{-}}$ in this luminescence system. The results indicate that the luminescence arises from two overlapping bands, one resulting from distant deep nitrogen donor to shallow acceptor recombination, the other a localized transition involving the nickel that accounts for the sharp structure.