Figure A.1

The dependencies of the \(\pmb{T_{1}^{-1}}\) rates as a function of temperature. Relaxation rates \(T_{1}^{-1}\) at magnetic field \(\mathrm{B}=10\mbox{ G}\) directed along the [100] direction as a function of temperature (a), and as a function of the estimated NV⁻ concentration for \(T=77\mbox{ K}\) (b). For comparison, we also plot previously reported experimental data from Ref. [26], obtained with samples S2, S3, and S8 at \(\mathrm{B}=25\mbox{ G}\) for various temperatures (c), and values of \(\mathrm{A}_{1}\) for \(T=10\mbox{ K}\) and different NV⁻ concentrations (d).