Monodisperse FePt nanoparticles were successfully synthesized using simple wet chemical method.

Fe₃O₄ was used as a magnetic shell around each FePt nanoparticles.

A theoretical model presented to calculate the shell thickness dependence of Coercivity.

Magnetic shells increase effective coupling between particles with increasing shell thickness.

Magnetization modes are more localized in the regions with higher exchange stiffness.