The effect of varying surface passivation and solvent environment on the dynamics of spin-lattice relaxation in iron oxide nanocrystals has been studied via pump-probe Faraday rotation measurement. Magnetization recovery through spin-lattice relaxation following photoinduced demagnetization was monitored in magnetite nanocrystals in various combinations of surfactants and solvents. The nanocrystals passivated with oleic acid did not exhibit any dependence of the dynamics of spin-lattice relaxation on the change of solvents viscosity and polarity. On the other hand, tetramethylammonium hydroxide (TMAH)-passivated nanocrystals dispersed in the water-propanol mixture exhibited faster spin-lattice relaxation with increasing water content. We envisage that the small surfactants such as TMAH allows solvent molecules to access the surface of the particles more readily and different solvent molecules providing different vibrational bath results in solvent dependent spin-lattice relaxation. More effective barrier between the surface and the solvent molecules formed by the longer surfactant (oleic acid) weakens such solvent effect.

Effect of surface and solvent environment on spin-lattice relaxation dynamics of iron oxide nanocrystals

244th National Meeting (2012)

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