Influence of Processing Methodology on Magnetic Behavior of Multicomponent Ferrite Nanocrystals

A novel and facile reverse microemulsion route has been developed for the synthesis of multicomponent ferrite nanocrystals, namely, Co0.5Zn0.5Fe2O4 and Ni0.5Zn0.5Fe2O4. In addition to microemulsions, these ferrite nanocrystals are also synthesized via a general chemical coprecipitation route. The crystals possess cubic spinel structure and spherical morphology as revealed by Fourier transform infrared (FTIR), X-ray diffraction (XRD), and field emission transmission electron microscopy (FETEM) analysis. The average diameters of Co0.5Zn0.5Fe2O4 and Ni0.5Zn0.5Fe2O4 nanocrystals obtained from chemical coprecipitation method are about 14 and 10 nm, respectively, and for those obtained from reverse microemulsion route they are calculated to be 5 and 2 nm, respectively. Vibrating sample magnetometery (VSM) reveals that the ferrite nanocrystals obtained from the reverse microemulsion route exhibit superparamagnetism whereas the ferrite nanocrystals obtained from chemical coprecipitation show ferromagnetism. The decrease in Curie (TC) and blocking (TB) temperature with size is attributed to the structural changes