Inducing glassy magnetism in Co-ferrite nanoparticles through crystalline nanostructure

摘要

This work reports on the study of three samples of 8 nm Co-ferrite particles prepared by standard methods based on the thermal decomposition of metal-organic precursors. Although all samples are single phase according to conventional techniques of structural and chemical characterization, they show strongly sample-dependent magnetic properties ranging from bulk-like ferrimagnetism to glassy magnetic behaviour. We show that the presence of crystallite domains associated with crystallographic defects throughout the particles leads to highly-frustrated ferrimagnetic cores that are responsible for the glassy phenomenology, while only samples almost free of structural imperfections show bulk-like magnetic properties. These results suggest the key role of the crystal quality in the large variability of magnetic properties previously reported for Co-ferrite nanoparticles. Besides, achieving control of the amount of structural defects in monodisperse, stoichiometric Co-ferrite nanoparticles can be an additional nano-structuring procedure to tailor their final magnetic properties.