Power-law versus exponential relaxation of 29Si nucleus spins in Si:B crystals

•29Si nuclear magnetization relaxation follows mixed power-exponential law.•Power-law corresponds to direct electron–nuclear relaxation.•Admixture of exponential relaxation corresponds to the nuclear spin diffusion.•Inhomogeneously distributed deformation defects are responsible for power low.•Homogeneously distributed Boron acceptors are responsible for exponential part.

The Si:B micro-crystals enriched with 29Si isotope have been studied by high resolution nuclear magnetic resonance (NMR) in the 300–800 K temperature range. The recovery of nuclear magnetization saturated by radiofrequency impulses follows pure power-law kinetics at 300 K, while admixture of exponential relaxation takes place at 500 K. The power-law relaxation corresponds to direct electron–nuclear relaxation due to the inhomogeneous distribution of paramagnetic centers, while exponential kinetics corresponds to the nuclear spin diffusion mechanism. The inhomogeneous distribution of deformation defects is a most probable reason of the power-law kinetics of nuclear spin relaxation.