Fig. 3. Spin relaxation time as function of the temperature T.

The relaxation time, τ, in milliseconds at B = 5 T as a function of the temperature is reported for the simulations of one electronic spin coupled to one nuclear spin and relaxing due to the modulation of the Zeeman and hyperfine energies by harmonic phonons (black line and dots), phonons with 1 cm⁻¹ of line width (red line and dots), and phonons with a linearly T-dependent phonon lifetime (green line and dots). A coefficient γ = 0.1 cm⁻¹/K is chosen. The experimental relaxation time as extracted from AC magnetometry (19) is also reported (blue dots and line).