Birefringence and transmission electron microscopy of maghemite-based biocompatible magnetic fluids

Static magnetic birefringence (SMB) and transmission electron microscopy were used to investigate maghemite-based magnetic fluids surface coated with citrate and dispersed in physiologic solution. The model used to investigate the birefringence signal considers the monomer and dimer contributions and dimer magnetic permeability dependence to the applied field. The particle size distribution obtained from the fit of the SMB data is compared to the data obtained from the microscopy. Zero-field birefringence, present in the birefringence data, was also taken into account, and analyzed by the dimer model.