Magnetic memory effect in self-assembled nickel ferrite nanoparticles having mesoscopic void spaces

Abstract

Self-assembled magnetic nanoparticles, which are fascinating for their potential applications in high-density data storage, nanoscale electronics, sensors, and medicines, attracted significant attention over the years. Controlled self assembly of magnetic nanoparticles is an art of chemical synthesis, because self assembly does not correspond to the thermodynamically minimum energy state. In order to construct the self-assembled nanostructure an input of external energy is required to direct the self assembly. In this article we report a novel approach of fabricating nanocrystalline and mesoporous nickel ferrite of 5–9 nm size particles by using supramolecular assembly of lauric acid (anionic surfactant) as a structure directing agent under hydrothermal conditions. Thermal, field and time variation of magnetization as well as careful studies of ageing effect clearly demonstrates strong interparticle interaction of the nanoparticle assembly. Interestingly, the memory effect is observed at low temperature as a consequence of interparticle interaction of the nickel ferrite nanoparticle assembly.