NMR and spin relaxation in systems with magnetic nanoparticles.

The ¹H NMR spectra and spin dynamics of the host systems have been studied in liquid and solid suspensions of γ-Fe₂O₃ nanoparticles. Significant broadening of ¹H NMR spectra and growing relaxation rates were observed with increased concentration of nanoparticles in the liquid systems, with the relation T₁/T₂ depending on the particular host. Solid systems demonstrate inhomogeneous broadening of the spectra and practically no dependence of T₁ upon the nanoparticle concentration. We explain the experimental results taking into account the predomination of self-diffusion as a source of the relaxation in liquid suspensions, and estimate effective parameters of relaxation in the systems under study.