Low-temperature spin relaxation inn-type GaAs

Low-temperature electron-spin relaxation is studied by the optical orientation method in bulk n-GaAs with donor concentrations from ${10}^{14}{\mathrm{cm}}^{-3}$ to $5\times {10}^{17}{\mathrm{cm}}^{-3}.$ A peculiarity related to the metal-to-insulator transition is observed in the dependence of the spin lifetime on doping near $n_D=2\mathrm{}\times {10}^{16}{\mathrm{cm}}^{-3}.$ In the metallic phase, spin relaxation is governed by the Dyakonov-Perel mechanism, while in the insulator phase it is due to anisotropic exchange interaction and hyperfine interaction