Size effect in the (PrF$_3$ nanoparticles-$^3$He) system

Spin kinetics of adsorbed and liquid $^3$He in contact with crystalline nanopowders of the Van Vleck paramagnet PrF$_3$ at a temperature of $1.5$ K has been studied by nuclear magnetic resonance. The correlation between the parameters of the nuclear magnetic relaxation of $^3$He and the sizes of the sample particles has been found. A qualitative model of the magnetic relaxation of $^3$He describing the experimental results has been proposed.