Synthesis and magnetic properties of the core–shell Fe$_{3}$O$_{4}$/CoFe$_{2}$O$_{4}$ nanoparticles

The Fe$_{3}$O$_{4}$/CoFe$_{2}$O$_{4}$ nanoparticles with a core–shell structure with an average size of 5 nm have been obtained by codeposition from the iron and cobalt chloride solutions. An analysis of the magnetic properties of the obtained system and their comparison with the data for single-phase Fe$_{3}$O$_{4}$ (4 nm) and CoFe$_{2}$O$_{4}$ (6 nm) nanoparticles has led to the conclusion about a noticeable interaction between the soft magnetic (Fe$_{3}$O$_{4}$) and hard magnetic (CoFe$_{2}$O$_{4}$) phases forming the core and shell of hybrid particles.