Challenging the frontiers of superparamagnetism through strain engineering: DFT investigation and co-precipitation synthesis of large aggregated Fe3O4 (magnetite) powder

Superparamagnetic magnetite (Fe3O4) has potential biomedical applications, but its synthesis can be challenging and costly. We present a simple and facile method for synthesizing superparamagnetic magnetite via the coprecipitation method. The pH and stabilizer concentration were optimized to obtain high purity Fe3O4 nanoparticles with superparamagnetic characteristics, despite having an aggregated morphology. The results showed that the synthesized particles were micrometer-sized, and exhibited superparamagnetic behavior with a value of 40 emu/g. The conventional wisdom on superparamagnetic behavior is to attribute the phenomenon to the presence of nanosized crystallites and nanoparticles in the aggregated structure, however, our computational analysis through density functional theory shows that strain-related effects are an underlying cause for the paramagnetism of magnetite as well, which explains our experimental observations. Overall, the co-precipitation method presented in this study offers an easy, non-toxic, and fast method for synthesizing Fe3O4 nanoparticles, which is suitable for industrial-scale production.