Achieving a noninteracting magnetic nanoparticle system through direct control of interparticle spacing

Monodisperse magnetite (Fe(3)O(4)) nanoparticles (NPs) were synthesized and coated using a SiO(2) shell with controlled thickness ranging from 3.0 to 20.0 nm. The temperature-dependent zero-field-cooled (ZFC) and field-cooled (FC) magnetizations of the 7.5 nm Fe(3)O(4) NPs with systematically increasing interparticle spacing were studied using the continuous and intermittent cooling protocol. The experimental evidence from dc magnetization and simulated ZFC/FC curves reveal that the increasing interparticle spacing modulated the collective magnetic behavior by effectively lowering the interparticle dipolar coupling, and for 7.5 nm Fe(3)O(4) NPs a noninteracting particle system formed with interparticle spacing above 31.5 nm.