Inhomogeneous broadening of optically detected magnetic resonance of the ensembles of nitrogen-vacancy centers in diamond by interstitial carbon atoms

We study the impact of the negatively charged nitrogen-vacancy (NV–) center density on the lattice strain resulting in the splitting of the optically detected magnetic resonance of HPHT diamond. A simple model, taking into account the presence of the interstitial carbon atoms, acting like a wedge force on the crystal lattice, explains the broadening and splitting of the optically detected magnetic resonance of the ensemble of NV– centers at densities within the range of 1013 ÷ 1014 cm−3. This model uses a complete generalized spin Hamiltonian, takes into account the strain-effect of each center in the ensemble and gives good agreement with experimental data.