Nuclear spin diffusion in a rare spin species

We derive an approximate theory for the spin diffusion tensor in a rare nuclear spin species imbedded into an abundant one, with special reference to 43Ca in CaF2. The usefulness of the theory is examplified by the description of an investigation of ferromagnetism with domains of the 19F spins, where the knowledge of the 43Ca spin diffusion constant allows a determination of the ferromagnetic domain thickness