1H relaxation of H2O enhanced by suspended α-Fe2O3 particles

Abstract

Spin-lattice and spin-spin relaxation measurements are performed on 1H in water molecules as a function of the concentration of suspended fine (1500 Å) α-Fe2O3 particles. To facilitate stability of the suspension and also to maintain a uniform distribution of the particles during the measurements, an aqueous colloidal suspension of α-alumina (Al2O3) is used for the diluting agent. The particle-concentration-dependent spin-lattice relaxation rates T1(c)−1 are analyzed with the Bloembergen–Purcell–Pound [Phys. Rev. 73, 679 (1948)] theory of spin relaxations in liquids by assuming that each particle possesses an average magnetic moment that is sitting at their centers. A departure from the Bloembergen–Purcell–Pound theory is noticed, namely a steeper concentration dependence than the usual linear one. The spin-spin relaxation measurements indicate the presence of strong diffusion effects. The magnetic-field gradient, which is deduced from the diffusion measurement, changes more strongly with the Fe2O3 particle concentrations than expected. The departures are attributed to the interactions between the magnetic moments of the Fe2O3 particles.