Proton spin diffusion in a nanodiamond

We report on a proton magnetic resonance study of a powder nanodiamond sample. We show that ¹H spin-lattice relaxation in this compound is mainly driven by the interaction of nuclear spins with unpaired electron spins of paramagnetic defects. We measured the spin-lattice relaxation time T ₁ by means of a saturation comb pulse sequence followed by dipolar dephasing, and plotted T₁ as a function of the dephasing time in different external magnetic fields. The received T₁ () dependence provides a striking manifestation of the spin diffusion-assisted relaxation regime. The obtained experimental data allow us to estimate the spin diffusion coefficient and spin diffusion barrier radius.