Synthesis and magnetic properties of highly crystalline Fe$_{3}$O$_{4}$ nanorods

Anisotropic one-dimensional magnetic nanostructures have drawn considerable attention due to their high surface to volume ratio, which drastically influences physical and chemical properties. In the past decade, most attention has been paid to the synthesis of Fe$_{3}$O$_{4}$ nanoparticles (NPs), mainly focusing on a spherical morphology. In this work, we report the first systematic study of the magnetic properties of highly crystalline Fe$_{3}$O$_{4}$ nanorods (NRs), which were synthesized by the hydrothermal method. XRD and TEM confirm the formation of highly crystalline Fe$_{3}$O$_{4}$ NRs with narrow size distribution. For high aspect ratio NRs (65\texttimes 6nm), room temperature saturation magnetization is close to that of bulk Fe$_{3}$O$_{4}$ (\textasciitilde 90emu/g) and much larger than that of spherical NPs of the same volume (60-70emu/g). DC magnetization vs. temperature data display a sharp change in the magnetization at 120K, which is attributed to the Verway transition, whose presence affirms the excellent crystallinity of Fe$_{3}$O$_{4}$ NRs. Owing to their high effective anisotropy and saturation magnetization, the Fe$_{3}$O$_{4\, }$NRs show enhanced heating efficiency relative to their spherical NP counterparts when tested in a standard hyperthermia set-up.