From Hollow to Dense Spheres: Control of Dipolar Interactions by Tailoring the Architecture in Colloidal Aggregates of Superparamagnetic Iron Oxide Nanocrystals


  • Financial support from CICYT (MAT2002–04001-C02) is gratefully acknowledged. P. Tartaj thanks the financial support from the Ramon y Cajal program.


The synthesis of spherical colloidal aggregates (see Figure) of superparamagnetic iron oxide nanocrystals with different packing fractions is reported. Using a mean-field model, the magnitude of dipolar interactions between nanomagnets has been correlated with differences in their assembly. The results could help understanding of the magnetic behavior of magnetic liposomes and hollow capsules, which are promising for drug delivery.