Hydrothermal synthesis, off-axis electron holography and magnetic properties of Fe3_{3}O4_{4} nanoparticles

The hydrothermal synthesis of Fe3O4 nanoparticles (NPs) (< 50 nm) from mixed FeCl3 / FeCl2 precursor solution at pH ~ 12 has been confirmed using complementary characterisation techniques of transmission electron microscopy and X-ray diffractometry. Off-axis electron holography allowed for visualisation of their single domain (SD) nature, as well as inter-particle interactions, with the latter attributed to explain the pseudo-SD/multi-domain behaviour demonstrated by bulk magnetic measurements